Petroleum Systems

BALTIMORE CANYON UNTESTED GAS POTENTIAL

Epstein, Samuel Abraham¹; Clark, Donald<sup>2

1</sup>Certified Petroleum Geologist 3701 173 Beach 134 th Street, Belle Harbor, New York, 11694, United States; ²Northeastern Science Foundation, Staten Island, New York, 10304, United States

Emerging markets (China, India, etc.) demand-pull for energy resources have altered the historical petroleum pricing cycle to the upside. As a result, frontier areas may require a reinvestigation using new technology or scientific knowledge. A prime example of this may be in the Baltimore Canyon Trough, offshore eastern United States.

Exploration in the Baltimore Canyon (32 wells) targeted Upper Jurassic and younger clastics and carbonates in structural traps. Five wells encountered hydrocarbons with cumulative flow rates testing 90 mm cfg/d (Ball, 1982). Apparent discontinuity in reservoir extent resulted in project abandonment.

Thus far, organic high mature source rocks have not been identified (Prather, 1991). An organic reinterpretation by (Sassen and Post 2007) of gas condensate from the Hudson Canyon suggests a deeper Lower Jurassic source, analogous to that of the U.S. Gulf Coast’s Smackover Formation, Late Jurassic in age. Even in the Smackover, a highly productive hydrocarbon reservoir, the identified source rock contained only a select few areas of organic rich source rocks (Sassen and Moore, 1998). Reprocessed seismic data (AVO Analysis) indicates reflectors typical of widespread salt layers deposited during the Early Jurassic (60 m thick and 25 km wide) (McKinney, et al, 2004) suggesting arid and restricted depositional climatic conditions in the Early Jurassic. Sea level rise during the Early Jurassic, suggested by Vail, could have set the stage for anoxic conditions and rich organic limestone sources similar to that found in the U.S. Gulf coast, dependent upon the degree of restrictions of the Proto Atlantic. Lacustrine syn-rift source rocks are found inter- fingering with the major evaporitic sequences (salt) in Gabon, West Africa.

Reservoirs should be in carbonates and shelf clastics as in the modeled Early Jurassic. (Lawerence et. al.1990) Analogous Smackover carbonates are extremely productive at depth (6100 meters). Early rift zone carbonates currently experience excellent reservoir characteristics (Epstein and Friedman 1983).

Impermeable evaporates and shales, between the Lower and Upper Jurassic, may provide excellent seals explaining the lack of significant migrated hydrocarbons in porous (30%) rocks of the Upper Jurassic and Cretaceous. Emplacement of igneous rocks from the Middle Jurassic to Cretaceous may have breached the trapped hydrocarbon. Lopatin calculations from a syn-rift section to the south (Bahamas) considered a cold basin (low geothermal gradient) match the core samples from the Baltimore canyon (Ro=.7 at 4250 meters) (Epstein and Brink, 1983). The igneous movements may have burnt out the older potential source rocks or the hydrocarbons diffused out.

A Baltimore Canyon Isopach map of the Triassic-Jurassic suggests that a significant area of Lower Jurassic age rocks is buried to depths of mature hydrocarbon generation (gas) (Schlee, 1980). The United States Geological Survey estimated a total of 500 million bbl of oil and 20 tcf of gas. (D. Dinofi, 1991).

Current depositional analogs are found along the East African Red Sea-Dead Sea-Sea of Galilee rift zone where carbonates, evaporates, and clastics are accumulating penecontemporaneously (Epstein and Friedman, 1981, 1982). In the Dead Sea, 5 km of subsidence has occurred since the Pliocene, reflected in the stratigraphic subsurface, exceeding that of the early Jurassic Baltimore Canyon deep trough.

Prospective areas should focus on deeper sections of Lower and Middle Jurassic nearer to the Baltimore canyon Jurassic depo-center at much greater depths than previously drilled and away from igneous emplacements.

PETROLEUM SYSTEMS OF THE U.S. CENTRAL ATLANTIC MARGIN

Post, Paul J¹; Sassen, Roger<sup>2

1</sup>MMS 1201 Elmwood Park Blvd., New Orleans, LA, 70123, United States; ²Dept. of Geology & Geophysics - Geochemical & Environmental Research Group - Texas A&M University, College Station, TX, 77845, United States

From 1975–1988, a single stage of expensive, disappointing hydrocarbon exploration took place on the U.S. Atlantic margin (USAM). Fifty-one wells (5 COST – 46 industry) were drilled in the Georges Bank basin, Baltimore Canyon Trough (BCT), and Southeast Georgia Embayment: none were drilled in the Carolina Trough.

Tested play types included drape/compaction structures, amplitude anomalies, listric fault traps, a dyke-swarm cored uplift, various carbonate margin plays, and slope-apron siliciclastics. The only positive results in the USAM were the gas encountered and/or tested in the eight wells drilled in the four-block Hudson Canyon (HC) 598 area, a listric fault trap in the BCT.

Analogs previously applied to USAM basins are inappropriate. While the same geologic age, they differ in regional and local setting. Carbonate and clean/mature siliciclastic reservoir analogs in the Gulf of Mexico Mesozoic basins are located on salt rollers, or related to salt-cored or salt-withdrawal structures. Other than in the Carolina Trough, similar structures are not widely recognized in USAM basins. The productive Sable sub-basin siliciclastic depocenter is located basinward from the carbonate margin and reservoirs are often overpressured, preserving porosity and permeability. In USAM basins, siliciclastic depocenters are generally landward from the margin and reservoirs encountered to date are not overpressured.

Throughout the USAM, issues regarding petroleum system elements include: generally degrading siliciclastic reservoir quality with depth, poorly developed carbonate reservoir facies, identification and areal distribution of source rocks, and timing of seal deposition/lithification in carbonate margin tests drilled to date. Petroleum system processes; i.e., timing of hydrocarbon generation–migration–accumulation are also poorly understood and appreciated.

Assessment of these basins using a forensic petroleum system approach may provide guidance for future exploration strategies.

COMPARING CONTROLS ON DEPOSITION OF MESOZOIC AND CENOZOIC MIXED CARBONATE-SILICICLASTIC SYSTEMS FROM THE CENTRAL ATLANTIC MARGIN, NORTH CAROLINA, USA

Coffey, Brian P.¹; Read, Fred<sup>2

1</sup>University of North Carolina/ N.C. Geological Survey 205 Perry Creek Drive, Chapel Hill, NC, 27514, United States; ²Virginia Tech Geosciences, 4044 Derring Hall, Blacksburg, VA, 24061-0420, United States

Regional lithology-based sequence stratigraphic frameworks constructed across the subsurface of the Albemarle basin of eastern North Carolina (USA) from Jurassic, Cretaceous, and Paleogene time intervals reveal striking similarities within each of these passive margin shelf successions. Studied units were deposited over a broad temporal range at very different paleolatitudinal positions and global climatic regimes.

Previous interpretation of the Paleogene depositional facies successions concluded that deposition was heavily influenced by paleolatitudinal position (subtropical to warm-temperate), oceanographic controls (boundary currents and nutrients), and with the major global transition from greenhouse to icehouse conditions. However, examination of more deeply buried Lower Cretaceous mixed carbonate-siliciclastic strata from the same basin reveals carbonate lithofacies that resemble late Paleogene updip shelf facies and stacking patterns consisting of admixed quartz sands/silts and mollusk-foraminifera dominated skeletal carbonate sands. Deep shelf marls also are comparable. Preliminary analyses suggest that facies similarities also exist into the underlying Upper Jurassic interval.

These observations suggest that while eustasy and climate strongly influence thickness and stacking patterns, the paleogeographic position of the shelf as a promontory exposed to open ocean wave energy and currents plays a major role in facies development through time. This region of the Atlantic margin was subjected to repeated pulses of ocean-derived elevated nutrient levels, similar to the modern palimpsest Carolina shelf. These observations further suggest that boundary currents (cool, proto-Labrador and warm, ancestral Gulf Stream) may have existed and mixed in this study area during Mesozoic times, albeit with lower intensities than observed in late Paleogene-Neogene icehouse conditions.

LITHOLOGY-BASED, HIGH-RESOLUTION SEQUENCE STRATIGRAPHIC FRAMEWORK OF LOWER CRETACEOUS, MIXED CARBONATE-SILICICLASTIC SEDIMENTS, ATLANTIC COASTAL PLAIN, EASTERN UNITED STATES

Sunde, Richard A. ¹; Coffey, Brian P. <sup>2

1</sup>Earth Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1s6, Canada; ²University of North Carolina / N.C. Geological Survey 205 Perry Creek Drive, Chapel Hill, NC, 27514, United States

A lithology-based sequence stratigraphic framework for the Lower Cretaceous mixed carbonate-siliciclastic sediments of the subsurface Albemarle Basin of eastern North Carolina was developed using thin sectioned well cuttings, wireline logs, and 2D seismic. Thin sections were analyzed to characterise lithology, fossil components, depositional facies, and diagenetic events, because the study interval is confined to the deep subsurface in a basin lacking core control. Integration of lithologic data with 2D seismic data and biostratigraphic control allowed regional correlation of major transgressive-regressive events between wells, resulting in the generation of a sequence stratigraphic framework for the onshore basin. Dominant lithofacies include: (shallow to deep): sandstone, skeletal sandstone, variably sandy mollusk packstone/grainstone, siltstone to shale, skeletal wackestone, variably sandy (quartz and glaucony) lime mudstone, and marl.

Comparison of observed facies with cores and wireline logs from the Baltimore Canyon and Southeast Georgia Embayment confirms that many updip sequences consist of upward-shoaling siliciclastic shoreface successions, with basal open shelf mollusk-rich carbonates often marking transgressive events. Basin-scale depositional trends indicate greater accumulation of the carbonate facies in the southern portion of the basin, with increased fine siliciclastic material to the north. This trend may reflect a major siliciclastic point-source in the vicinity of the ancestral Chesapeake region. The depositional and diagenetic models generated provide insight into the facies and reservoir properties in coeval offshore units comprising frontier exploration targets along the Western Atlantic margin of the U.S. and Canada.

RIVER SOURCE AND DISPERSION OF LOWER CRETACEOUS SANDS, SCOTIAN BASIN

Pe-Piper, Georgia¹; Triantafyllidis, Stavros¹; Piper, David J.W.<sup>2

1</sup>Saint Mary's University 933 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada; ²Geological Survey of Canada Atlantic, Dartmouth, Nova Scotia, B2Y 4A2, Canada

Understanding the source and dispersion of Lower Cretaceous deltaic sandstones is important for predicting (1) the distribution of sandstone; (2) the availability of quartz; and (3) regional variation in diagenesis. Many analytical techniques to identify sediment provenance have been applied to samples from conventional cores from offshore Scotian basin wells and fields ranging from Naskapi N-30 in the west to Dauntless D-45 in the east. The results were compared with similar analyses of onshore Chaswood Formation samples.

Geochronology of detrital monazite shows several modes: ~330 and ~400 Ma at the Naskapi N-30 well; ~400 Ma in wells from the Alma field to the Venture field, with minor ~1.0 and ~1.65 Ga modes; and predominant ~1.0 and ~1.8 Ga modes at the Peskowesk A-99 well, with a minor ~380 Ma mode. Detrital zircons show similar modes. However, the ~1.0 Ga mode predominates from the Alma field to the Venture field, and an additional ~650 Ma mode is present. Morphology and texture show that 45–80% of detrital zircon is of first cycle igneous origin, with the proportion of polycyclic zircon decreasing stratigraphically upward. Sources of monazite and zircon are further constrained by mineral chemistry. Variation in abundance and chemical composition of heavy minerals, notably chromite, tourmaline and garnet, has been determined.

Bulk-rock geochemistry provides information on the total source area, whereas mineralogical studies emphasize source rocks containing heavy minerals. The Ti content of Scotian basin shales is almost double the world average due to detrital ilmenite. Fe is also abundant and Ca very low. Sandstones show geochemical variability within the basin; however, shales are more uniform geographically.

The integration of this data suggests that the Naskapi N-30 well was supplied by a river that also furnished sediment to the Chaswood Formation in central Nova Scotia. The sandstones in the area from the Alma field to the Venture field were sourced from a major river draining Newfoundland. Sandstones on the eastern Scotian Shelf were sourced by one or more separate rivers, also draining Newfoundland.

OLIGOCENE CANYON AND FAN DEVELOPMENT: THE RESPECTIVE ROLES OF SEA LEVEL AND SEDIMENT DELIVERY IN EVOLUTION OF THE EASTERN SCOTIAN MARGIN

Brake, Virginia¹; Mosher, David ²; Wach, Grant<sup>3

1</sup>Dalhousie University Dalhousie University, Room 3006, Life Sciences Centre, Halifax, Nova Scotia, B3H 4J1, Canada; ²Geological Survey of Canada- Atlantic, Dartmouth, Nova Scotia, B2Y 4A2, Canada; ³Dalhousie University, Room 3006, Life Sciences Centre, Halifax, Nova Scotia, B3H 4J1, Canada

The Cenozoic sedimentary section of the eastern Scotian margin is characterized as a progradational sequence incised by canyons, valleys and gullies. These features provide conduits for offshelf sediment transport, slope by-pass and deposition on the continental rise and abyssal plain during periods of low relative sea level. The Stonehouse 3D seismic volume, spanning outer shelf and upper slope terrain of a portion of the modern eastern Scotian Slope, provides an opportunity to study the detailed Cenozoic stratigraphy and modern and buried seafloor morphologies in this critical shelf to slope transition zone. Sequence stratigraphic concepts were applied to the Neogene section of this depth-migrated 3D data set to map the distribution of seismic facies and their bounding unconformities. Several widespread unconformity surfaces were identified and compared to the present-day seafloor. Canyon incision appears to be episodic throughout the Cenozoic section. As with the modern seafloor, ancient canyon systems are fundamental to slope sedimentary processes and sediment delivery mechanisms. Canyon formation requires significant removal of slope material to the deep ocean floor, following which these canyons act as sediment pathways. A particularly widespread Oligocene (?) erosive surface has a complex morphology that is potentially analogous to the modern Sable Gully canyon system that “drains” much of the central and eastern Scotian Shelf through a system of feeder channels and valleys. The implications of repeated canyon formation on the Scotian Slope imply that the residence period of sediments on the slope is geologically short and that preservation potential is confined to periods of canyon fill or local reductions in gradient. Canyon formation on the slope presumably requires significant sea level lowering, so repeated canyon formation raises the question of eustatic versus tectonic controls on sedimentary processes. Given the extent of the Oligocene (?) erosional unconformity, it is suggested that eustatic change alone cannot explain this consequence, thus tectonic inversion on this passive margin may have contributed to sea level lowering.

UNUSUAL JURASSIC CONDENSATE OF THE HUDSON CANYON AREA, U.S. ATLANTIC

Sassen, Roger ¹; Post, Paul J.<sup>2

1</sup>Geochemical and Environmental Research Group (GERG) 833 Graham Road, College Station, TX, 77845, United States; ²U.S. Department of the Interior, Minerals Management Service, Office of Resource Evaluation / 1201 Elmwood Park Blvd., New Orleans, LA, 70123, United States

Gas and minor condensate was discovered in Late Jurassic and Early Cretaceous reservoirs in the Hudson Canyon (HC) 598 area of the Baltimore Canyon Trough (BCT).

The oldest sedimentary rocks in the BCT are interpreted to be Triassic syn-rift deposits. Predominantly carbonate Early to Middle Jurassic units overlie the Triassic and underlie the Late Jurassic–Early Cretaceous siliciclastic reservoirs.

Condensates from the Kimmeridgian (HC 598-1) and Albian (HC 642-2) reservoirs originate from the same source rock. While biomarkers are absent or in low relative abundance in the condensate, diamondoids, consisting primarily of adamantane and diamantane, along with their methyl and ethyl derivatives, are relatively abundant. The diamondoids have been concentrated during intense thermal cracking of an original oil. The carbon isotopic properties of the condensate are extremely enriched in ¹³C (-23.7‰ to -24.6‰ PDB), consistent with a Jurassic marine kerogen source. Triassic source rocks appear unlikely to have sourced these condensates because Triassic-sourced oils in the Newark and Culpepper basins are strongly depleted in ¹³C. The unusual geochemistry of the condensate is interpreted to be the result of extreme thermal cracking of oil sourced from the underlying Early to Middle Jurassic carbonate-rich source rocks. Diamondoid maturity indices suggest that the maturity of the condensate ranges from ~1.3% to ~1.6% vitrinite reflectance (R_o), significantly higher than the estimated ~0.9% R_o of the deepest Kimmeridgian reservoir. Vertical migration of deeper, more mature hydrocarbons into shallower reservoirs was facilitated by faults connecting the source and the reservoir.

The enrichment of diamondoids and ¹³C are similar to condensates sourced by the Late Jurassic Smackover Formation of the U.S. Gulf Coast. The role of Jurassic oil-prone source rocks in the Central Atlantic is underappreciated.

FUTURE PROSPECTS OF OIL AND GAS WITHIN SELECTED TARGET AREAS OF SCOTIAN SHELF AND SLOPE, OFFSHORE NOVA SCOTIA, EASTERN CANADA: EVALUATION BASED ON PETROLEUM SYSTEMS RISK ASSESSMENT

Mukhopadhyay (Muki), Prasanta K.¹; Harvey, Paul, J.<sup>2

1</sup>Global Geoenergy Research Ltd. ,, Halifax, --, B3J 2A1, Canada; ²Nova Scotia Department of Energy, Halifax, NS, B3J 3P7, Canada

Recent deepwater drilling surrounding the Sable Subbasin within the Scotian Slope, Eastern Canada has indicated that the successes/failures in finding economic hydrocarbon discoveries are closely related to complex petroleum systems and mobilization of Jurassic salts compared to deepwater basins of both the Gulf of Mexico and Angola. New comprehensive research combining seismic stratigraphy, heat flow assessment, geochemical fingerprinting, and petroleum system modeling of the Triassic-Tertiary sediments from the Scotian Slope reveals that the formation, timing, and fluidity of several large allochthonous salt canopies (Sable Subbasin) or autochthonous salt diapers (area between Sable and Shelburne Subbasins) are closely connected to source rock anoxicity, bypassing of turbidite sands (in early Tertiary and late and middle Cretaceous), and the survival of hydrocarbons within various play types. Early mobilization of Jurassic salt forming large canopies (especially within the Tertiary sediments of the Sable Slope) possibly originated from enhanced heat flow and three-phase fluid flow in the late Jurassic-early Cretaceous. Our study indicates that the various play types (especially the salt flank and salt top reservoirs) in the late Jurassic and early Cretaceous may possibly be charged with three petroleum system hydrocarbons (gas-condensate, light oil-gas and heavy oil-gas) within the Sable (beyond 2500m water depth) and Shubenacadie-Shelburne Slopes (beyond 1500m). The late Triassic/Early Jurassic lacustrine and Jurassic/Cretaceous Verrill Canyon marine source rocks are the most significant components within various petroleum system hydrocarbons although the timing of hydrocarbon charge could be significantly different in various parts of the Scotian Basin.

MID TO LATE CRETACEOUS STRUCTURAL AND SEDIMENTARY ARCHITECTURE AT THE TERRA NOVA OILFIELD, OFFSHORE NEWFOUNDLAND – IMPLICATIONS FOR TECTONIC HISTORY OF THE NORTH ATLANTIC

Sinclair, Iain¹; Withjack, Martha O.<sup>2

1</sup>Husky Energy Suite 901, Scotia Centre, 235 Water St., St. John's, NL, A1C 1B6, Canada; ²Rutgers University, Geological Sciences, 610 Taylor Road , Piscataway, NJ, 08854-8066, United States

Multiple exploration, delineation, and development wells, in association with a high-quality 3D seismic survey over the Terra Nova oilfield, provide a detailed data set for the analysis of the mid to Late Cretaceous structural and stratigraphic development of the Jeanne d’Arc basin on the Grand Banks of Newfoundland.Closely spaced wells allow for recognition of multiple parasequences of shoreface to shelf silciclastic sediments deposited during falling relative sea level in Hauterivian through Barremian time.The northward translation of the coastline with progressive truncation of the parasequences to the south demonstrates that regional uplift of the southern margin of the Jeanne d’Arc basin occurred during and immediately following deposition of these progradational parasequences.The upper bounding surface, defined by an angular unconformity with widespread evidence of valley incision, is dated as mid-Aptian.Highly variable thicknesses of back-stepping coastal plain, shoreface and marine shelf strata document a long-term increase in relative sea level accompanied by abrupt changes in subsidence rates occurring across W- to NW-striking, syn-depositional normal faults active during the mid-Aptian through Middle or Late Albian. What do these patterns of uplift, subsidence, and faulting reveal about the tectonics of the Jeanne d’Arc basin during the mid-Cretaceous? Specifically, are the W- to NW-striking normal faults related to gravity-driven processes or plate-tectonic processes?Although the basin tilting and the presence of Triassic/Jurassic salt would support gravity-driven processes, erosion in the south and deposition in the north would inhibit the northward flow of salt.Additionally, evidence of synchronous detached shortening is lacking.Basement-involved extension would produce W- to NW-striking subsalt and suprasalt normal faults.These decoupled faults occur exclusively to the east of the border fault of the Jeanne d’Arc basin (i.e., the Murre fault).Thus, the Murre fault would have had both normal and strike-slip components of displacement during the mid-Cretaceous extension.

EARLY INFILL OF THE TRIASSIC FUNDY BASIN: ARCHITECTURE OF THE WOLFVILLE FORMATION AND FLUVIAL EVOLUTION.

Leleu, Sophie¹; Hartley, Adrian J.²; Jolley, David W.²; Williams, Brian P.J.<sup>2

1</sup>University of Aberdeen Meston Building, Aberdeen, Scotland, AB24 3UE, United Kingdom; ²Meston Building, Aberdeen, Scotland, AB24 3UE, United Kingdom

The Fundy Basin forms one of a series of early Mesozoic rift basins developed along the north-western Atlantic margin. Syn-rift continental sediments were deposited during Late Triassic times within the basin. The sedimentary succession comprises the lower fluvio-aeolian Wolfville Fm, the overlying ephemeral fluvial/playa Blomidon Fm capped by basaltic lava (Olsen et al., 1989; Wade et al., 1996). Three sub-basins are present in the Fundy Basin: the Fundy sub-basin, the Minas sub-basin to the east and the Chignecto sub-basin to the north. The Wolfville Fm displays a complex interplay of coarse and fine-grained fluvial sandstones, aeolian dune deposits and alluvial fan sediments. This study focuses on the Wolfville Fm stratigraphy and correlation within the gravely- and younger sandy-dominated fluvial deposits of the Minas sub-basin. This contribution will present a detailed analysis of the large scale architecture (27 km) of a gravely braided river system deposited within this endorheic basin, and will discuss the major changes in fluvial style within the basin. The palaeogeography of the Wolfville Fm is analyzed by determining the size of the braided river system and by taking an allostratigraphic approach to the recognition and correlation of extensive bounding surfaces. The bounding surfaces and cycles within both coarse and fine-grained fluvial units allow correlation across the basin. Together with a palynological analysis, the stratigraphy of the Wolfville Fm is assessed in the Minas sub-basin. This new scheme of the Wolfville Fm architecture in a better constrained timescale has the potential to help predict sand-fairways and reservoir architecture within similar coarse grained alluvial deposits.

CONTINENTAL RIFT BASIN FILLS: EVOLUTION FROM OPENED TO CLOSED STAGE (WOLFVILLE/ BLOMIDON FM, NOVA SCOTIA).

Leleu, Sophie<sup>1

1</sup>University of Aberdeen Meston Building, Aberdeen, Scotland, AB24 3UE, United Kingdom

Rift basins in continental settings tend to display a similar sedimentary evolution with an initial stage (1) characterized by alluvial fan deposition around the basin flanks and fluvial sequences in the basin centre and a later stage (2) dominated by lacustrine sedimentation in the basin centre. The syn-rift Late Triassic sedimentary succession of the Minas sub-basin (Bay of Fundy, Nova Scotia) shows this evolution. The sedimentary succession comprises the lower fluvio-aeolian Wolfville Fm (stage 1 deposits) and the overlying ephemeral fluvial/lacustrine/ playa Blomidon Fm (stage 2 deposits). This contribution presents a facies analysis of the transition between the two stages. The Wolfville Fm displays a complex interplay of coarse and fine-grained fluvial sandstones, aeolian dune deposits and alluvial fan sediments. The upper part of the Wolfville Fm (250 m of vertical section) which occurs beneath and is transitional into the lacustrine/ playa deposits of the Blomidon Fm is described here. Cyclicity within the sedimentary succession is illustrated by well organized and repetitive alternations of fluvial/ ephemeral fluvial/ lacustrine and aeolian sediments, which suggests a gradual evolution from stage 1 and stage 2 and a strong climatic influence on depositional architecture.

SEAFLOOR DIAGENESIS OF THE SCOTIAN BASIN: THE ROLE OF FE, TI AND P

Okwese, Ann Chioma¹; Pe-Piper, Georgia²; Piper, David J.W<sup>3

1</sup>Saint Mary's University 923 Robie Street, Halifax, Nova Scotia, B3H3C3, Canada; ²923 Robie Street, Halifax, Nova Scotia, B3H3C3, Canada; ³Geological Survey of Canada, Dartmouth, Nova Scotia, B2Y4A2, Canada

Diagenesis in Lower Cretaceous sandstones of the Scotian basin is an important reservoir quality. Diagenetic processes include the effects of seafloor redox-controlled changes in pore water and the re-mineralization of organic matter; as well as later cementation and secondary porosity resulting from increases in the temperature and pressure with burial and the flux of formation waters and hydrocarbon expelled from compacting shales. Lower Cretaceous rocks of the Scotian basin are deltaic, with cycles of delta progradation characterized by high sedimentation rates capped by transgressive systems tracts typified by low sedimentation rates.

Transgressive systems tracts (TST) in one well (Peskowesk A-99 with 7 conventional cores) from the Scotian basin were identified in conventional cores with the support of available wireline logs, and core photographs (CNSOPB Geoscience Research Laboratory). The TST sediment facies include bioturbated medium- to coarse-grained sandstones with patchy siderite cementation and some bioclasts, grading upward into bioturbated mudstones. Geochemically, the Lower Cretaceous sedimentary rocks of the Scotian basin are unusual in having high titanium (Ti) and iron (Fe) and very low calcium (Ca). As a result, the early diagenetic system is dominated by Fe minerals and locally by phosphorus (P) minerals. Samples have been collected from conventional cores through representative TSTs and underlying high-sedimentation rate deltaic sandstones in the Peskowesk A-99 well for whole-rock geochemical analysis. The vertical variation in particular Fe, Ti and P can be used to understand the seafloor diagenetic system and its relationship to abrupt changes in sedimentation rates in the TST.

DISTRIBUTION OF DIAGENETIC MINERALS IN LOWER CRETACEOUS SANDSTONES WITHIN A DEPOSITIONAL FACIES AND SEQUENCE STRATIGRAPHIC FRAMEWORK: GLENELG, THEBAUD AND CHEBUCTO FIELDS, OFFSHORE SCOTIAN BASIN

Karim, Atika¹; Pe-Piper, Georgia²; Piper, David J.W.<sup>3

1</sup>Saint Mary's University Departement of Geology, 923 Robie St. , Halifax, Nova Scotia, B3H 3C3, Canada; ²Departement of Geology, 923 Robie St. , Halifax, Nova Scotia, B3H 3C3, Canada; ³Geological Surevy of Canada, Dartmouth, Nova Scotia, B2Y 4A2, Canada

The spatial and temporal distribution of diagenetic cements has been constrained in relationship to lithofacies and sequence stratigraphy of the Lower Cretaceous sandstones from the Glenelg, Chebucto and Thebaud fields in the Sable Subbasin. Coated grains of illite and chlorite occur in transgressive systems tracts (TST) in Glenelg N-49 and Thebaud I-93 and are cemented by Fe-calcite. Early kaolinite occurs as booklets and vermicular stacking textures principally in sandstones immediately beneath the TSTs, particularly in cross-bedded, coarse-grained, channel sandstones. Illite occurs as fibrous crystals, which in the Chebucto K-90 are included by ankerite. Fe-rich chlorite rims, found only in the Thebaud samples, have developed from earlier Fe-rich clay. Early pore-filling chlorite occurs in contact with detrital quartz lacking quartz overgrowths and is commonly associated with illite. Quartz cement, well developed in medium and coarse grained sandstones, postdates kaolinite and predates most other cements. Calcite, Fe-calcite, Mg-calcite, ankerite and siderite are the major cementing minerals in the studied wells. In Glenelg H-59, two siderite cements were defined; the earlier one occurs in TSTs as large, corroded crystals and is low in Mg. The late microcrystalline siderite (< 10 μm) is Mg-rich (~ 9 wt.%). It forms the tiny crystals that fringe detrital grains and fill intercrystalline micropores. Early calcite cement is found principally in bioturbated sandstones and mudstones with bioclasts, typical of the highstand systems tract (HST). In samples from the Glenelg field, perthite is replaced by Fe-calcite. Late framboidal pyrite in carbonate cement indicates burial under both reducing and alkaline conditions. Rare traces of francolite (1 to 6wt.% P₂O₅) are found in the Glenelg wells associated with illite and calcite cements. This study demonstrates that the distribution of diagenetic minerals and their impact on reservoir-quality evolution can be better elucidated when linked to a sequence stratigraphic framework.

SECOND-ORDER SEQUENCES AND THEIR APPLICATION FOR EXPLORATION IN THE DEEP-WATER SCOTIAN SLOPE

Davies, Andrew¹; Etienne, James L²; Mike, Simmons D²; Davies, Roger B²; Sharland, Peter R²; Sutcliffe, Owen E<sup>2

1</sup>Neftex Petroleum Consultancy Ltd 115BD Milton Park, Abingdon, --, OX14 4SA, United Kingdom; ²115BD Milton Park, Abingdon, --, OX14 4SA, United Kingdom

Large-scale changes in lithofacies and stratigraphic architecture resulting from relative sea-level changes have been a prime research focus for the past few decades. Within industry, prediction of hydrocarbon play elements using sequence stratigraphic techniques is well-established. In 2001 we demonstrated the veracity of a sequence stratigraphic model for the Arabian Plate identifying 63 major Maximum Flooding Surfaces (MFS) and Sequence Boundaries (SB). Ongoing work, incorporating nearly all of Earths sedimentary basins, now demonstrates the occurrence of 118 biostratigraphically constrained sequences that are global and observed independent of tectonics or sediment supply. The rapidity and magnitude of sea-level changes inferred from our model implicate eustatic forcing. In Eastern Canada, recent exploration has shifted focus towards the deepwater of the Scotian Slope driven by successes in other circum-Atlantic deepwater basins. Despite a proven petroleum system, the slope remains underexplored. Sandy lowstand fans comprise the principal reservoir targets, but are risky, borne out by few commercial successes. Biostratigraphically constrained sections from the Scotian Shelf provide a framework within which sequence stratigraphy can be applied. The recognition of large hiatus relating to second-order SB’s allows prediction of viable lowstand reservoirs down systems-tract. For example, the absence of Early Paleocene in many shelf wells, relates to an important late Maastrichtian SB during which significant down-slope transport of sediment is predicted. Major transgressions are often associated with development of organic-rich facies. Such is the case for Naskapi Member source rocks which relate to a second-order intra-Aptian MFS. Here, major second-order sea-level fluctuations are identified which are postulated to have exerted an important control on reservoir and source rock development on the Scotian Slope.

INTEGRATED RESERVOIR CHARACTERISATION, DEEP PANUKE GAS POOL, OFFSHORE NOVA SCOTIA

Corbett, Norman¹; Uswak, Gordon ²; Skrypnek, Terrance (Terry)<sup>2

1</sup>EnCana Corporation EnCana on 9th 150 -9th Avenue PO Box 2850, Calgary, Alberta, T2P 2S5, Canada; ²EnCana on 9th 150 -9th Avenue PO Box 2850, Calgary, Alberta, T2P 2S5, Canada

The Deep Panuke gas pool is the first, significant carbonate reservoir gas discovery on the Scotian Shelf. Development of the pool is currently proceeding. The Jurassic Abenaki Formation-hosted (Eliuk, 1978), lean, slightly-sour gas accumulation was delineated in two rounds of drilling involving seven wells resulting in five successes (Weissenberger, 2006). Well test rates exceed 50 million cubic feet per day per well.

Diagenesis controls secondary porosity development in the Deep Panuke fractured dolostone and associated leached vuggy limestone reservoir (Wierzbicki et al, 2006). Three litho-types were defined in the reservoir characterisation process: non-reservoir unleached limestone, porous vuggy limestone and dolostone. Petrophysical analysis of the wells defines relationships between lithology, porosity, Sw and fracturing for each litho-type. In particular, it has been important to recognize the presence of a bimodal porosity distribution in the High Permeability Reef Front (HPRF) region of the pool which contains 80% of the gas resource. The bimodality is a consequence of the presence of both dolostone and unleached limestone litho-types. Similar reservoir characteristics have been documented at Simonette, Alberta (Duggan, 2004). Neural Net methods were used to integrate the petrophysical results with 3D seismic-derived rock properties, resulting in bimodal low/mid/high case porosity predictions for the HPRF. This multi litho-type approach and aquifer modeling has led to significant improvements in the integrated reservoir characterisation, well test matches and in the static and dynamic reservoir simulation models.

The approved development plan (EnCana, 2006; CNSOPB, 2007) involves subsea tie-back of wells to a new jack-up production field centre and new export pipeline to shore.

References

CNSOPB, 2007, Deep Panuke Offshore Gas Development, Canada-Nova Scotia Benefits Plan Decision Report and Development Plan Decision Report, Canada-Nova Scotia Offshore Petroleum Board (CNSOPB) 108 p., available online at www.cnsopb.ca

Duggan, J.P., 2004, Burial Dolomites at Swan Hills Simonette Reef, West Central Alberta Basin, Can.Soc.Petrol.Geol. 2004 Dolomite Conference, 29 p.

Eliuk, L.S., 1978, The Abenaki Formation, Nova Scotia Shelf, Canada – A Depositional and Diagenetic Model for a Mesozoic Carbonate Platform, Bull. Can. Petrol. Geol., V. 26, No. 4, p. 424-514.

EnCana, 2006, Deep Panuke Development Plan, available online at www.deeppanukereview.ca/publicrecord/index.html

Weissenberger, J.A.W., R.A. Wierzbicki and N. J. Harland, 2006, Carbonate sequence stratigraphy and petroleum geology of the Jurassic deep Panuke field, offshore Nova Scotia, Canada, in P. M Harris and L. J. Weber, eds., Giant hydrocarbon reservoirs of the world: From rocks to reservoir characterization and modeling: A.A.P.G. Memoir 88/SEPM Special Publication, p.395-431.

Wierzbicki, R., J.J. Dravis, I. Al-Aasm, and N. Harland, 2006, Burial dolomitization and dissolution of Upper Jurassic Abenaki platform carbonates, Deep Panuke reservoir, Nova Scotia, Canada: AAPG Bulletin, V.90, No. 11, p. 1843-1861.

HYPERPYCNAL RIVER FLOODS AND THE DEPOSITION OF LOWER CRETACEOUS SANDS, SCOTIAN BASIN

Piper, David J.W.¹; Karim, Atika²; Pratt, Heidi²; Noftall, Ryan ²; Gould, Kathleen²; Foley, James²; Pe-Piper, Georgia<sup>2

1</sup>Geological Survey of Canada (Atlantic) Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, NS, B2Y 4A2, Canada; ²Department of Geology, Saint Mary's University, Halifax, NS, B3H 3C3, Canada

The large supply of sand to the Scotian Basin in the latest Jurassic and early Cretaceous, resulting from tectonic reactivation of the Appalachian hinterland, produced coarse-grained braided rivers preserved in the Chaswood Formation. Such rivers have the propensity to discharge hyperpycnally during floods. The importance of such hyperpycnal flows can be evaluated from sedimentological criteria in conventional core. Thick bedded reservoir sandstones from fields such as Thebaud and Venture appear to be inner shelf hyperpycnal deposits (facies 9), forming graded sandstone beds decimeters to metres thick, with Bouma Ta-Tc sequences, abundant phytodetritus, detrital intraclasts of mudstone and siderite, and minor bioturbation at the top of beds. This facies passes stratigraphically upward into tidally influenced river-mouth and river-channel sandstones (facies 4) and downward into thinner graded sandstone beds with interbedded mudstone (facies 0). Highly bioturbated thin bedded sandstones (facies 2) in places show hummocky cross-stratification, concentration of shells at the base of beds, and wave-ripples, suggestive of storm reworking. In the Glenelg field, tidally-influenced hypopyncal silts interbed with hyperpycnal sands and both change character distally. Turbidites in the middle Missisauga Formation at Tantallon show petrography and sedimentary structures that indicate deposition from overbank hyperpycnal flows. Exploration models for the Scotian Basin must take account of this reinterpretation of the major sandstone facies. The presence of widespread hyperpycnal flows means that there may have been major transfer of sand to deep water. The rapid deposition of hyperpycnal flow sands, overlain by slowly sedimenting transgression surfaces, may have strongly influenced the style of early diagenesis and the neoformation of iron-rich clays that transformed on burial to chlorite rims.

PALEOCEANOGRAPHIC AND PALEOENVIRONMENTAL IMPLICATIONS FOR HYDROCARBON EXPLORATION OF THE CONTINENTAL SLOPE OFF NOVA SCOTIA

Jansa, Luba F.<sup>1

1</sup>Emeritus Scientist Geological Survey of Canada-Atlantic, Dartmouth, N.S., B2Y4A2, Canada

The continental slope off Nova Scotia has recently become of interest for oil exploration as a potentially new gas province, under the assumption that past success in exploration on the shelf can be extended onto the continental slope. Is such an assumption supported by the sediment depositional history on the shelf and by the general paleoceanography of the Central Atlantic Ocean during the late Mesozoic?

Of all elements of the Petroleum System, only the source rock and presence of reservoir rocks will be discussed. Source rock occurrences depend on marine organic matter generation and preservation. The former are controlled by the availability of nutrients supplied either by continental runoff (therefore controlled by climate), or as a result of coastal upwelling, surface water mixing, and open ocean divergence. Could such conditions have developed during the Mesozoic on the Scotian Slope? An additional constraint to be considered is ocean bottom water oxygenation, as such conditions changed dramatically during Mesozoic-Cenozoic time in the Central Atlantic. During the Late Jurassic, Late Cretaceous and early Cenozoic, oceanic bottom waters in this region were highly oxygenated, resulting in the destruction of organic matter deposited in ocean bottom sediments. In contrast, the middle Cretaceous was a period of organic matter preservation in deep sea and marginal basin sediments, either due to changes in deep water circulation, climate and/or increases in depositional rates.

Occurrence of reservoir rocks is another important parameter to be considered. The existence of both sandstone and carbonate reservoirs was proven by drilling on the shelf. For continental slope exploration, the petroleum industry applied known models of turbidite fans, apparently without giving sufficient consideration to the sediment supply and sea level changes affecting development of the shelf area during the Cretaceous. This may prove to be the major factor in a lack of commercial hydrocarbon discoveries in exploration wells drilled on the Scotian Slope. Deeper understanding of the geologic evolution of the continental margin and paleoceanographic conditions affecting it, together with a modification of exploration strategy are needed to improve the success of hydrocarbon exploration in the Scotian upper slope domain.

THE PENICHE BASIN:TECNO-SEDIMENTATION AND EXPLORATORY ASPECTS

França, Almério Barros¹; Gontijo, Rogério Cardoso¹; Bueno, Gilmar Vital<sup>1

1</sup>Petrobras Avenida Chile, 65 sala 1401, Rio de Janeiro, RJ, 20031-912, Brazil

Petrobras in partnership with Galp and Partex, has acquired a total of 12.000 Km² in the Peniche Basin, offshore Portugal – a counterpart of some Northeast North American basins. The main subject of the present work is to show some geological aspects of the Peniche Basin, based mostly on seismic data and a few wells drilled nearby. There is no well drilled in the whole concession area.

The Jurassic Peniche Basin is bounded by SW-NE lineaments, subdividing the basin into horst and grabens and, by NW-SE lineaments, most likely transfer faults. From the end of the Jurassic onward, compressional stress seems to have predominated, reactivating old lineaments, creating thrusting faults and a series of flower structures. Normal faulting associated with sediment growth due to salt movement (middle to late Jurassic) are also a common feature in seismic lines. Uplifting in the shallow portion of the Peniche Basin brought about slumping and rotation of huge blocks in deep water realm.

Three major unconformities are easily mapped in seismic, corroborated by well data: 1) base of lower Cretaceous; 2) pre upper Jurassic sequence (strongly erosive), and 3) Cretaceous-Tertiary boundary. The erosive phases associated with all the above unconformities have great potential of sediment transport deep into the basin suggesting the possibility of sandstones reservoirs, either channelized or unconfined lobes. Channelized, coarse grained Cretaceous sandstones are well exposed along the coast in Santa Cruz, Portugal. The wells drilled shallow in the basin have shown porosity ranging from 15% to 30% (Cretaceous) and 15% in deeper sandstones (Jurassic).

Carbonates are another possibility as reservoir rocks with porosity ranging from 15% to 20%. Bioconstruction, probably rudist reefs such as the ones exposed in several onshore locations and along the coast, such as Praia do Guincho, near Estoril.

The potential source rocks (Pliensbachian and Kimmeridgian), present in outcrops and wells in the Lusitanian Basin, have been traced to deep horizons in the Peniche Basin, where the sedimentary section is thicker, suggesting greater potential than the shallow areas.

CONTINENTAL SLOPE SEDIMENTATION MODELS: LAURENTIAN CHANNEL AND HALIBUT CHANNEL REGIONS, EASTERN CANADA

Giles, Michael ¹; Mosher, David²; Piper, David²; Nedimovic, Mladen³; Wach, Grant<sup>3

1</sup>Dalhousie University 3006 Department of Earth Sciences, Dalhousie University, Halifax, NS, B3H 4J1, Canada; ²Geological Survey of Canada (Atlantic), BIO, Dartmouth, Nova Scotia, B2Y 4A2, Canada; ³3006 Department of Earth Sciences, Dalhousie University, Halifax, NS, B3H 4J1, Canada

Recently acquired seafloor multibeam, and 2D and 3D seismic reflection data of the St. Pierre and Halibut Slope regions provide evidence for successive mass failures at a variety of scales. The occurrence of stacked and regionally extensive mass failures suggests that this is a fundamental process for slope sedimentation in this area; the most recent mass-transport event was in 1929. There are a variety of factors that explain the significance of mass failures in this area: 1) Drainage of the Great Lakes, which are the largest inland bodies of water in North America, cause the St. Lawrence River and Laurentian Channel to act as major fluvial and sediment transport conduits for most of eastern North America. It was also a major ice-outlet corridor during numerous Quaternary glaciations. As a result, sedimentation rates at the mouth of Laurentian Channel and on Laurentian Fan have been periodically high, leading to potential generation of high pore pressures and a thick column of underconsolidated sediment. 2) Sediment sampling in the region has shown the presence of intra-formational methane gas within the shallow portion of the sediment column. Generation of gas within sediment reduces its strength properties. 3) Gas hydrates, which may be indicated by bottom-simulating reflectors, are interpreted to occur in the region. Their dissociation may provide another potential source for shallow gas. 4) Recognition of buried sedimentary bedforms suggests sandy intervals underlying St. Pierre and Halibut Slope areas. Listric faults extending from surface escarpments into this interval suggests that possible detachment surfaces, perhaps in response to generation of overpressures occur within them. 5) The area overlies the Cobequid-Chedabucto fault, a paleo-transform margin, which appears to have a higher level of seismicity than most of the Canadian east coast margin. Ground accelerations due to earthquakes plays a critical role in initiating sediment failure, as in the 1929 Grand Banks submarine landslide during a M7.2 earthquake. Mass transport processes are clearly a significant mechanism of sediment delivery in the shelf to slope setting of the greater Laurentian Channel region. These processes are dependent upon a variety of pre-conditioning factors, both lithologic and structural, yet likely initiated by seismicity. The ubiquitous nature of such processes in the Quaternary section is a critical component to understanding reservoir potential of underlying rocks that reside in the same geologic setting.

A QUANTITATIVE 3D OUTCROP MODEL OF A GRAVEL DOMINATED FLUVIAL SYSTEM (LATE TRIASSIC, MINAS BASIN, NOVA SCOTIA, CANADA)

van Lanen, Xavier¹; Hodgetts, David²; Redfern, Jonathan²; Williams, Brian³; Leleu, Sophie<sup>3

1</sup>PhD student Williamson Bld, Oxford Road, Manchester , Lancashire, M13 9PL, United Kingdom; ²Williamson Bld, Oxford Road, Manchester , Lancashire, M13 9PL, United Kingdom; ³Department of Geology & Petroleum Geology, King's College, Aberdeen, Aberdeenshire, AB24 3UE, United Kingdom

The Wolfville Formation was deposited in a rift basin setting during Anisian to Norian age. It is superbly exposed in both cliff sections and on extensive wave-cut platforms along the Minas Basin shore, Nova Scotia (Canada). This nature of the exposure provides unique three-dimensional sections, offering a valuable insight in the sedimentology and the facies geometries and distribution of a red bed braided fluvial-aeolian facies suite.

The selected study area is located on the southern Minas Basin shore and represents the lower unit of the Wolfville Formation. The area measures 400 m by 350 m and comprises Carnian to Norian age sediments that show a cyclicity of conglomerate / pebbly rich sandstone to a coarse lithic sandstone with sparse pebble sized clasts. The limited amount of preserved finer grained material throughout this gravel dominated system contains the faunal remains and palaeosol horizons. The base is characterised by the discordant contact with the Carboniferous and a thin alluvial breccia unit.

To obtain quantitative outcrop data, both LiDAR and DGPS data were collected and integrated with traditional geological field and laboratory data into a digital outcrop model (DOM). In the DOM the observed geological object are mapped and their geometries and distribution evaluated. The results offer a better understanding of the depositional system, and provide a geological framework for reservoir models. Such information aids improved reservoir characterisation and geostatistical modelling, as well as help explain seismic reflection data and improve flow model simulations for subsurface reservoirs.

CONTROLS ON FACIES DISTRIBUTION AND RESERVOIR DEVELOPMENT OF UPPER TRIASSIC RIFT CONTINENTAL SYSTEMS IN INTERMONTANE RIFT SETTINGS: A COMPARATIVE STUDY OF EXTENSIVE OUTCROPS IN SW MOROCCO

Redfern, Jonathan¹; Mader, Nadine²; Fabuel Perez, Ivan³; Hodgetts, David³; El Ouataoui , Abedelmajid<sup>4

1</sup>University of Manchester Williamson building, Oxford Road, Manchester, Gt Manchester, M139Pl, United Kingdom; ²Hess Ltd, London, Greater London, WC2N 6AG, United Kingdom; ³Williamson building, Oxford Road, Manchester, Gt Manchester, M139Pl, United Kingdom; ⁴ONHYM, Rabat, xx, 10050, Morocco

Upper Triassic (Carnian) sediments in SW Morocco comprise a continental red bed sequence deposited in discrete rifted basins following the break up of Pangea and opening of the Atlantic. This comparative study examines extensive outcrops of the Oukaimeden Sandstones Formation (F5) in the High Atlas and Unit T6 in the Argana Basin, SW Morocco, deposited within a series of narrow fault bounded intermontane basins. Both contain a variety of braided fluvial, overbank, shallow ephemeral lacustrine, alluvial fan and aeolian facies.

Traditional sedimentological data (sedimentary facies logs, palaeocurrent information, gamma ray logs etc) has been combined with high resolution 3D laser (LIDAR) and Differential Global Positioning System (DGPS) to map these outcrops and provide a detailed dataset.

On a basin scale, the often complex facies distribution evident in the Argana Basin suggests a highly variable fill within these basin types. Correlation of individual facies elements is often difficult and relies on identification of key stratal surfaces. Local tectonics control accommodation and influence facies patterns, such as development of alluvial fans and entry points of major drainage systems. Significant changes in fluvial style, from ephemeral to perennial, are recognized in both basins within this interval, which suggests rejuvenation of the source areas and a potential interplay of climatic and tectonic control. An overall drying upward pattern is observed, with increasing influence of aeolian processes towards the top of both the Oukaimeden sandstone (F5) and T6 of Argana. This supports previous work that has demonstrated a change from humid to increasingly arid conditions during the Upper Triassic, recognized both throughout SW Morocco and in the Fundy Basin, Canada, and highlights the climatic control on the depositional system.

These studied sections offer potential analogues for subsurface Triassic hydrocarbon systems in similar settings, and provide valuable information on the tectonic and climatic control on depositional facies and architecture. Analysis of basin-wide facies variation, provenance and sediment pathways provide regional scale analogue data. More detailed field scale reservoir models have also been developed for the high net:gross intervals in the Oukaimeden sandstone.

PERMO-TRIASSIC BASINS FROM IRELAND TO NORWAY: BASIN ARCHITECTURE AND CONTROLS

Shannon, Patrick M.¹; Stolfova, Katerina<sup>2

1</sup>University College Dublin UCD School of Geological Sciences, University College Dublin, Belfield, Dublin, 4, Ireland; ²UCD School of Geological Sciences, University College Dublin, Belfield, Dublin, 4, Ireland

Permo-Triassic strata are locally preserved in a swath of elongate basins of various shapes and sizes along the European margin of the North Atlantic. The burial of these basins beneath Jurassic, Cretaceous and Cenozoic strata, combined with tectonic effects of later rifting and continental breakup, means that the original extent and the large-scale depositional geometries of these basins are poorly constrained. This study uses seismic data, supplemented by core, wireline and outcrop information, to document the extensive development of proven (but poorly dated), largely non-marine, Permo-Triassic strata along the Irish, UK and Norwegian Atlantic margins. Data are examined from basins of different sizes, thicknesses and structural settings in the European North Atlantic region. A wide range of regional depositional geometries is identified within the Permo-Triassic to lowermost Jurassic succession. In some areas basins show pronounced asymmetry, controlled by long-standing reactivated faults. In other areas subtle broad fault-controlled geometries with switching fault polarities are documented. In yet other areas the Permo-Triassic to Lower Jurassic succession is characterized by simple uniform thicknesses across large regions. The basin architecture is controlled by a complex interplay of crustal thickness and thermal structure, inherited Variscan, Caledonian and older basement fabrics, inherited palaeotopography and the spatial and temporal rift history.

MIDDLE CENOZOIC DEPOSITIONAL PROCESSES ALONG THE WESTERN SCOTIAN MARGIN

Campbell, Calvin¹; Mosher, David²; Wach, Grant<sup>3

1</sup>Dalhousie University Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada; ²Geological Survey of Canada Atlantic, Dartmouth, Nova Scotia, B2Y 4A2, Canada; ³Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada

Extensive 2D and 3D seismic exploration data on the deep water margin off Nova Scotia reveals prospective hydrocarbon bearing structures, yet seven recent exploration wells met with only moderate success. The difficulties encountered in finding quality reservoirs reveal that geologic models successfully applied in other parts of the world need to be refined for the Scotian margin. It is the purpose of this study to develop an understanding of margin-scale geologic process relevant to the middle Cenozoic section of the Scotian margin in order to develop appropriate exploration models.

Published studies of the Oligocene to Pliocene geological history of the outer Scotian margin show that canyon incision on the slope and local depositional lobe progradation dominates sedimentation during periods of relative sealevel lowstands. During this same period, development of Antarctic glaciation and opening of Arctic Ocean circulation established North Atlantic oceanic currents that influenced sedimentation on the lower slope and rise. There is also evidence for occasional tectonic activity, presumably due to changes in intracrustal stress, salt migration, and movement along ancient faults. Throughout the Cenozoic, large scale sediment mass-wasting events wield considerable influence over the evolution of depositional systems along parts of the margin.

Preliminary analysis of 2D and 3D seismic reflection data from the western Scotian margin reveals evidence of widespread erosion and associated depositional elements which, through correlation with biostratigraphic data at the Shubenacadie H-100 and Shelburne G-29 wells, are of Oligocene to Miocene age. Here, the geological history of the outer margin records a complex interplay of down-slope and along-slope processes. The relationship of these various processes; sea level change, canyon cutting, contour current intensification, tectonics, sediment slope by-pass and sediment instability, for example, is unknown at this time but is critical, both for understanding the geology of the Scotian margin and how continental margins evolve in general.

THE MOHICAN CHANNEL GAS HYDRATE ZONE, SCOTIAN SLOPE: GEOPHYSICAL STRUCTURE

Cullen, Janette¹; Mosher, David C²; Schlesinger, Angela³; Haacke, Ross⁴; Louden, Keith<sup>5

1</sup>Department of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada; ²Geological Survey of Canada - Atlantic, Natural Resources Canada, P.O. Box 1006, Dartmouth, Nova Scotia, B2Y 4A2, Canada; ³School of Earth and Ocean Sciences, University of Victoria, P.O. Box 3055, Victoria, BC, V8W 3P6, Canada; ⁴Geological Survey of Canada, Natural Resources Canada, P.O. BOX 6000, Sidney, BC, V8L 4B2, Canada; ⁵Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada

The Cenozoic section of the Scotian margin largely consists of turbidity current, mass transport and glacial sediments, with related canyon and valley formation. A significant portion of the continental slope of this margin falls within the methane gas hydrate stability zone (GHSZ), yet a prominent bottom simulating reflector (BSR) was identified at only one location. 3D seismic reflection, ocean bottom seismometer (OBS) and long offset (9 km) pre-stack 2D multichannel seismic data were used to study the velocity structure, geophysical characteristics and volume of this Mohican Channel gas hydrate zone. The Mohican Channel area shows a double BSR 0.35 to 0.45 s below the seafloor within channel levee deposits in water depths of 1,200 to 1,500 m. Primary and secondary BSRs are ~280 km² and 50 km² in area. A system of polygonal faults extends from an apparent gas-charged zone at ~1.2 s subbottom (Miocene-Eocene Unconformity) to ~0.3 s subbottom. Some faults form vertical chimneys and appear as conduits for gas leakage into the GHSZ. Some chimneys reach the seafloor producing positive-relief gas-charged mounds. A total of 39 OBSs were deployed along 3 profiles; one strike line and 2 dip lines. A few of the P and S-wave velocity profiles derived from these data over the BSR show anomalies consistent with the presence of hydrate and free gas, but others are ambiguous. Dissimilarities within the low velocity zone (LVZ) and amplitude variations suggest hydrate is laterally inhomogeneous. Shear-wave anisotropy appears related to changes in density of polygonal faults. As in any petroleum system, source, pathway, reservoir and trapping mechanisms are necessary for hydrate occurrence. Rare appearance of BSRs on the Scotian margin with low gas and hydrate concentrations imply that gas hydrates are in far less abundance than theoretical calculations suggest.

REVISITING THE EAST GEORGES BANK BASIN, OFFSHORE NOVA SCOTIA - WHAT THE EXPLORATIONISTS SAW TWO DECADES AGO

Koning, Tako<sup>1

1</sup>Advisor, Tullow Oil Angola No 43, Largo Ingombotas, --, Luanda, Angola

The East Georges Bank Basin is located offshore Nova Scotia on the southeastern Canadian continental shelf. The basin covers 10,000 square kilometers (2.5 million acres) and is one of the last undrilled basins in North America.

The geological understanding of this basin is based on 16,000 km of seismic data which was studied and interpreted in the 1980’s by Texaco Canada’s geoscientists. The first public presentation of the interpreted data was at a CSPG-GAC-MAC conference in 1988 in St. John’s, Newfoundland and thereafter the geological and geophysical interpretations were presented at a number of oil industry conferences worldwide (San Diego, Calgary, Lagos, Rio de Janeiro). This presentation is a re-presentation of the 1988 and subsequent papers. In 1988, the government placed an oil activity moratorium on Georges Bank. No activity such as seismic surveying has taken place since that time. Therefore, although this presentation is based on old seismic data, it must be viewed as up-to-date since no new data has been acquired on the bank for well over twenty years.

The overall Georges Bank Basin formed during the Triassic when the landmass of Pangea began separating along rift zones. A prominent Paleozoic basement high, the Yarmouth Arch, separated the East Georges Bank Basin from the West Georges Bank Basin, and had a dominant influence on sedimentation until Middle Jurassic. During the Middle Jurassic, major growth faulting and halokinesis commenced in the basin.

The structural and stratigraphic evolution of the East Georges Bank Basin has resulted in the development of a number of economically attractive seismically-defined prospects. The Geological Survey of Canada (GSC) published in 1983 (Proctor et al) that the average hydrocarbon expectation of the basin was 168 x 10⁶m³ barrels oil (1.0 billion barrels) and 150 x 10⁹m³ natural gas (5.3 TCFG). The GSC’s speculative estimate for the basin was 350 x 10⁶m³ barrels of oil (2.1 billion barrels) and 307 x 10⁹m³ gas (10.8 TCFG).

PETROLEUM SYSTEMS DEVELOPED ALONG THE NW AFRICA OFFSHORE MARGIN: CHALLENGES FACING EXPLORATION & PRODUCTION COMPANIES

Chaney, Alistair John<sup>1

1</sup>Tullow Oil 3rd Floor, Building 11, Chiswick Park, 566 Chiswick High Rd,, London, NA, W4 5YS, United Kingdom

The offshore NW African Atlantic margin extends from northern Morocco to the Guinea Fracture Zone in the south and comprises up to 6km of Mesozoic and Cenozoic silicilastics and carbonates overlying Triassic salt.

The primary source rocks are Albian, Cenomanian and Turonian mudrocks, with lesser contributions from Palaeocene intervals that are thought to have reached marginal maturity in some areas, and restricted Liassic shelfal carbonates. Deep water gravity deposits provide the main reservoirs and include confined canyon systems and unconfined turbidite lobes. Less well explored plays include carbonate reefs and deltaic topsets further up-dip. The most prominent trapping mechanism along the length of the NW African margin is related to halokinesis. Allochthonous salt diapirs and canopies (largely absent from offshore Western Sahara, Senegal, Gambia and Guinea Bissau) have generated proven and unproven traps including sub-salt, salt stock, and supra salt closures. Other trapping mechanisms include tilted fault blocks (some are counter regional faults), stratigraphic pinchout (Banda gas discovery), extensional roll-over folds, and toe trust compressional folding.

The under explored nature of the NW African Atlantic margin provides E&P companies with numerous challenges. The lack of detailed well control makes prediction of sandstone problematic, particularly as many of the canyons appear to be by-pass systems. Where geobodies have been mapped, lack of seismic imaging makes it difficult to differentiate with confidence between prospective sheet turbidite sandstones and reservoir-poor debrites, particularly in the deeper Cretaceous section. Other pitfalls have recently come to light after drilling. These include reef-like morphologies along the carbonate platform break of slope that are possibly contourites of siliceous ooze, and bright seismic amplitude anomalies that are not hydrocarbon filled sands, but low velocity shales.

These challenges are generally prospect specific, but there are further difficulties which relate to the cost of exploration in immature basins. Increasing water depth places restrictions on rig availability, and requires increasingly larger prospects to be considered commercially viable. As the restrictions imposed by the water depth drive companies to explore deeper in the basin it becomes more likely that prospects will be overpressured as they are in other deep passive margins (e.g. Nigeria, Borneo). This will only increase well costs, placing greater pressures on commerciality.

GEOLOGY AND HYDROCARBON POTENTIAL OF THE NW AFRICAN ATLANTIC MARGIN

Davison, Ian <sup>1

1</sup>Earthmoves Ltd. Chartley, 38-42 Upper Park Road, Camberley, Surrey, Gu15 2EF, United Kingdom

The NW African Atlantic Rift System began to open in Carnian times (ca. 235 Ma) and produced a series of half graben with red-bed clastic fill in Morocco. Near the end of rifting, a 1-2 km thick salt was deposited, and is interpreted to be the same age as the CAMP volcanic rocks (200±1 Ma). Farther south, the deep Triassic rifts have not been drilled, but they could contain good oil prone source rocks similar to the southern USA basins. New evidence is presented that salt is present along the Cap Boujdour area of Aaiun Basin 450 km farther to the south of present mapped salt limit. The salt on the North American margin may also extend farther south, linking the South Georges Basin with the Baltimore Canyon Stone Dome occurrence. The northern limit of the Moroccan salt basin is currently mapped to terminate at the overthrust southern edge of the Rif Thrust Belt, but the salt must continue northward below the Rif. A sub-thrust play exists in Northern Morocco, which has never been tested due to the lack of good imaging below the thrust belt. The Cenomanian-Turonian source rock may be mature in this area, due to the tectonic loading in the Oligo-Miocene. The overlying Jurassic sequence is mainly a carbonate slope facies, but occasionally a rimmed platform edge developed (Senegal, Gambia and Mauritania). The carbonate play has still to be fully tested, because the wells drilled on the USA margin appear to miss the rimmed carbonate edge, and very few wells have drilled the carbonates in NW Africa. The carbonate platform eventually became drowned in the Early Cretaceous, when clastic deltas were deposited. The increased clastic sediment input may be due to the internal rifting and flank uplift occurring throughout North Africa. Cretaceous -Cenozoic clastic sediments constitute the main deepwater target reservoirs. Recent wells in Morocco appear to have failed due to lack of reservoir.

REGIONAL SETTING OF THE LATE JURASSIC DEEP PANUKE FIELD, OFFSHORE NOVA SCOTIA, CANADA – CUTTINGS-BASED SEQUENCE STRATIGRAPHY AND DEPOSITIONAL FACIES ASSOCIATIONS ABENAKI FORMATION CARBONATE MARGIN.

Eliuk, Leslie<sup>1

1</sup>Dalhousie University and GeoTours Consulting Inc Box 852 (91 Creighton St.), Lunenburg , Nova Scotia, B0J 2C0, Canada

Deep Panuke, discovered in 1998, is the only carbonate gas field in the eastern North America continental shelf. Several recently published studies (Weissenberger et al., 2006; Wierzbicki et al., 2005, 2006; EnCana 2006) give details on the hydrothermally-dolomitized reef margin gas field itself. Expanding on those studies using mainly cuttings and core data, Panuke is placed in a larger context between the northeast contemporaneous major Sable Island paleodelta prograding ramp shelf and the southwest thicker cleaner carbonate platform. Wells can be grouped based on geometry and position relative to the shelf margin as follows: prograding ramp margin (only a few of the numerous wells in the Sable Island paleodelta are included), margin slope, margin with full shoaling sequence, margin with paleohighs and encased pinnacles (typical of Deep Panuke area), margin inboard flexure with shoals, interior platform oolitic shoals, interior platform shaly lagoon and ‘moat’ and near-shore ridge/siliciclastic-rich. The large-scale (second order?) vertical full-shoaling stratigraphic sequence is seen in nearly all margin wells. It comprises a basal transgressive oolite usually, then forereef with microbial mud mounds, then shallow coral-coralline sponge reefs, then oolites and two types of capping beds – either oolites (with or without sandstone interbeds) or lithistid sponge-rich beds. Only Deep Panuke does not show this pattern. Laterally there is a curious pattern to the argillaceous sponge-rich cap beds in being flanked by wells with oolite caps both nearer the delta and southwestward of the Panuke area wells. There is also a regional trend in the color from darker to lighter (and finally even red in the slope beds) away from the Sable Island paleodelta. These facies trends relative to the Sable Island delta and the associated early, deep prodeltaic burial are key factors that contributed to Deep Panuke’s reservoir, trap, seal and charge properties.

ABENAKI CARBONATE MARGIN FACIES ASSOCIATIONS: POSTER 1 - UPDATED DEPOSITIONAL FACIES TEMPLATE AND VERTICAL-LATERAL MARGIN VARIATIONS AS PIE DIAGRAM SECTIONS-MAPS

Eliuk , Leslie<sup>1

1</sup>Dalhousie University Earth Sciences & GeoTours Consulting Box 852 (91 Creighton St), Lunenburg, Nova Scotia, B0J 2C0, Canada

Although artificially static, a carbonate facies template and schematic carbonate facies model are useful for high-lighting the general relationship of facies in a dip transect of a carbonate platform from shore to basin. The biological-sedimentological criteria in cuttings and core for facies association identification are thus tabulated. However contemporaneous local variability such as channels versus reef buildups versus skeletal shoals at the margin are more difficult to show sometimes even on 3D models. And in some cases facies many not be contemporaneous locally such as argillaceous sponge reef beds versus clear-water deeper coral or microbialite reefs or mounds. While perhaps in the same depositional depth and relative position, they occur widely separated in space and/or time but are shown on a single facies template or model for practical presentation and simplification. Modified from Wilson (1975) template by Eliuk (1978), Eliuk and Levesque (1988) then Wierzbicki, Harland and Eliuk (2002), the Abenaki facies associations are as follows: 1) Open marine shale – bathyal/deep, 2) open marine shale – neritic/shallow, 3A) foreslope channel, 3B) proximal foreslope (forereef), 3C) distal foreslope including microbial mounds (see 5C), 4A) ‘deep’ siliceous sponge reef mound & intermound, 4B) ‘shallow’ siliceous/lithistid sponge mound, 4C) ‘shallow’ lithistid-stromatoporoid/coral sponge reef, 5A) skeletal rich, 5B) shallow coralgal reef (coral-coralline sponge), 5C) pelleted ‘mud’ (see 3C), 5D) oolitic, 5E) oncolitic, 5F) thin bypass sandstones, 6) ‘moat’ open inner shelf (deep lagoon), 7) mixed carbonate-siliciclastic platform interior (nearshore ridge), 8) coastal deltaic-interdeltaic-restricted lagoon (loferite)-continental (coals). As discussed in the accompanying talk, geometry and position relative to the shelf margin (see seismic in Kidston et al. 2005) is another way of subdividing the well ‘magnafacies’ especially when they have a particular vertical depofacies pattern. Yet another method of viewing relative changes is showing percentage lithofacies-essential biotic-sedimentological components on pie diagrams placed vertically on sections or areally on maps by stratigraphic sequences.

ABENAKI CARBONATE MARGIN FACIES ASSOCIATIONS: POSTER 2 - SLOPE-FOREREEF SETTINGS AND SPECTRUM OF MICROBIAL MUD/REEF MOUNDS

Eliuk, Leslie<sup>1

1</sup>Dalhousie University Eath Sciences & GeoTours Consulting Box 852 (91 Creighton St), Lunenburg, --, B0J 2C0, Canada

With the exception of M-79 in Deep Panuke and Cohasset D-42 that is a bit back of the margin flexure, all thick shelf margin wells (Marquis L-35 & L-35A, Cohasset L-97, Dominion J-14, Musquodoboit E-23, Demascota G-32, Acadia K-62, Albatross B-13) have a significant portion of their lower and middle sections (lower Baccaro Member or EnCana’s Sequences 2 and 3) in a microbial-hard peloid-carbonate mudstone lithofacies rich in calcite cements. These lithofacies are interpreted as distal carbonate slope with microbial mud/reef mounds. This is strongly supported by core (G-32, K-62, sidewall cores in B-13 and core at the base of the Baltimore Canyon Trough ‘Civet’ OCS-0337 well) which show isopachous submarine cements, marine geopetals, microbial thrombolitic-stromatolitic and even stromatactis textures. The amount and variety of associated biota, degree and openness of submarine cavity systems and presence of debris flows varies, possibly systematically with distance from the Sable Island delta. Color changes show this with B-13 most distal and white and red. In contrast, two wells with core (Penobscot L-30, West Venture C-62) in the Sable Island paleodelta with prograding ramp geometries have microbial mud mound facies that are considerably darker and less biotically varied compared to those of cores in wells to their southwest. Queensland M-88 is the only well drilled completely on the Abenaki carbonate slope to test possible bypass sandstone reservoirs immediately basinward of the Deep Panuke field. Cuttings, strongly supported by drilled sidewall cores, indicate a distal slope setting with abundant microbial mud/reef mound facies. An exception is thin sponge or stromatoporoid-rich limestone beds that define the sequence boundaries with overlying often-black shales. Proximal slope or forereef facies are fairly common in most margin wells especially in Deep Panuke. There, these generally sandier carbonates are often ‘leached’ limestones or dolomites forming much ofthe porous reservoir. Even in core distinguishing forereef from reef flat sands can be a difficultinterpretive problem. However in the Margaree F-70 core, the inclined dips and interbedding of thin in situ relatively low-energy hence deeper-water microbial-sponge-microsolenid coral reeflets support a proximal forereef interpretation for the dolomites and graded echinodermal grainstone interbeds.

ABENAKI CARBONATE MARGIN FACIES ASSOCIATIONS: POSTER 3 - VARIETIES OF REEFS AND REEF MOUNDS OF THE OUTER MARGIN

Eliuk, Leslie<sup>1

1</sup>Dalhousie University Earth Sciences & GeoTours Consulting Box 852 (Creighton St), Lunenburg, Nova Scotia, B0J 2C0, Canada

Worldwide, the Late Jurassic is noted for great quantities of varied reefs and of hydrocarbons in carbonates. Surprisingly, with just a handful of exceptions, it is not the Jurassic reefs that contain the hydrocarbons but rather platform interior carbonates in structural traps. Deep Panuke is one of those exceptions. The gas is in the reef complex and the trap is partially stratigraphic with even the structural component mainly due to reefal growth. And in the Abenaki margin, all three Jurassic reef-reef mound end-members (Leinfelder’s, 1994) are present: coral reefs, siliceous sponge and microbial (mud) reef mounds. These end-members have intermediate transitional forms but only the shallow-water coral-coralline sponge (stromatoporoids and chaetetids) reef complexes are significant reservoirs. Microbial mud/reef mounds (see poster 2) are well-cemented limestones and occur in slope facies below the reservoir levels. (As a caution against generalizations, some Jurassic Gulf of Mexico microbialite reefs occur in restricted shallow settings and are hydrocarbon reservoirs.) Siliceous (lithistid) sponge reefs (see poster 5) generally occur above the porosity-reservoir levels and actually contribute to the trap seal by their argillaceous content. These three reef type end-members can be distinguished even in cuttings. But only in core can one appreciate and possibly subdivide the shallow-water reef complex into reef flat, core (typically rubbly from bioerosion then storm and wave action) and proximal forereef (cores in Cohasset L-97, Margaree F-70, Panuke H-08, Demascota G-32, Acadia K-62). And in most cases the common presence of carbonate mud in the matrix, crinoidal debris and encrusting microbialites indicate that, unlike many modern Acropora-dominated reefs, these Late Jurassic hexacoral-rich reefs probably grew in slightly deeper margin water not at the crest. Probably particularly true when large phaceloid corals are seen still standing (L-97 core and on FMI in Panuke M-79). Seismic and dip-meter data clearly show that the reef-prone outer margin slope, between the updip oolitic inner flexure and the distally steepened downdip flexure, has considerable local topography. Some forereef beds on local pinnacle-like buildups even dip landward (F-70, MarCoh D-41). Usually that topography is encased by carbonates but Dominion J-14 shows that rarely shale can be trapped between individual buildups. In Baltimore Canyon Trough, the southward extension of the Jurassic gigaplatform, margin pinnacle reefs keep growing as the shelf interior is drowned and buried in shale.

ABENAKI CARBONATE MARGIN FACIES ASSOCIATIONS: POSTER 4 - SHELF EDGE OOLITIC SHOALS OF THE INNER MARGIN AND ONCOLITE, BYPASS SAND, UNCONFORMITY THOUGHTS

Eliuk, Leslie<sup>1

1</sup>Dalhousie University Earth Sciences & GeoTours Consulting Box 852 (Creighton St), Lunenburg , Nova Scotia, B0J 2C0, Canada

Worldwide, Jurassic carbonates are also noted for oolites. The Abenaki too has oolite nearly everywhere and in many cases it allows cyclic and sequence subdivision to be made. But rarely are these grainy rocks an important contributor to reservoir porosity at least in the deeply buried Panuke trend, in the carbonate ramp shelf associated with the Sable Island paleodelta, in the basal transgressive beds of the platform, or in the very oolitic Scatarie Member at the base of the Abenaki Formation. Seismically at the inboard margin flexure and sedimentologically, oolites occur in the shallowest carbonate settings and should be subject to effective winnowing and subaerial exposure. Both should create porosity but likely Late Jurassic calcitic seas may have made for less soluble ooids. And most oolites are completely occluded by burial cement except on the Western Shelf where they occur less deeply buried beneath the present-day deep-water slope. At Deep Panuke the oolitic grainstones are impermeable enough to form part of the seal for stratigraphic trapping as opposed to their usual role as platform reservoir rock . A very thick oncolitic facies was defined using core in Acadia K-62 where the common presence of ooids, megalodont clams and coral fragments with the large oncoids suggested a reef flat interpretation. Since the oncolite facies is not obvious in other wells, speculatively it may reflect a more local or special event - possibly nutrient enrichment corresponding to the influx of deltaic clays and siliceous sponge reefing closer to the Sable Island delta. Another facies definitely related to siliciclastic influx is thin bypass sands. These are widespread at particular levels and have been interpreted to represent unconformity related low-stand periods with sand influx. As well the sand may overlie unconformities when reworked during the next transgression. In bracketing the inferred unconformities they represent maximum regression surfaces. Thus they are a key to establishing a sequence stratigraphic framework on the platform whether that is based on transgression-regression or more elaborately on relative sea-level stands of transgressive, high, forced regression and low.

ABENAKI CARBONATE MARGIN FACIES ASSOCIATIONS: POSTER 5 - SPONGE REEFS AND ARGILLACEOUS SPONGE-RICH CARBONATES RELATED TO DELTAS: THE JURASSIC-CRETACEOUS BALTIMORE CANYON-NOVA SCOTIA ABENAKI EXAMPLES COMPARED TO THE MODERN FRASER PRODELTA EXAMPLE.

Eliuk, Leslie<sup>1

1</sup>Dalhousie University Earth Sciences & GeoTours Consulting Box 852 (91 Creighton St), Lunenburg, Nova Scotia, B0J 2C0, Canada

Of the three Jurassic reef-reef mound end-members (see poster 3), the siliceous sponge reef mounds occur uniquely at the top of the Abenaki and at the top of equivalent carbonates in the Baltimore Canyon Trough (BCT). Then shales overlie both. A major oceanographic or relative sea-level carbonate drowning event or series of events affecting both areas seemed like an obvious explanation. However a limestone core just below the Venture Field shelf margin delta, diachronous age dating of sponge-rich beds and their limited distribution on the Nova Scotia shelf (NSS), and the discovery of siliceous sponge reefs adjacent to prodeltaic shales of the Fraser River delta, British Columbia (Conway, Barrie and Krautter 2004), may give an alternative explanation with a modern analogue. Seismic and Ringer’s Valanginian model ( in Eliuk and Prather 2005, repeated at this conference) in BCT show that after and perhaps even contemporaneously with the shelf margin pinnacle reefs, sponge mounds formed in nearby deeper water (several 100 feet or ~50-100m) below the pinnacle reef and in front of small deltas prograding over drowned inner platform carbonate. In the NSS, argillaceous sponge-rich beds at the top of the Abenaki are younger in wells further southwest of the large Sable Island delta. Even further away from the delta on the Western Shelf the Abenaki (Roseway unit) carbonates no longer have a sponge facies but continue in typical shallow platform facies and are younger yet. In the bottom of West Venture C-62 the older thin Late Jurassic #9 Limestone has a few metre thick sponge-stromatoporoid-microbial reef mound capping a pure microbialite reef mound of similar thinness. Laminated black prodeltaic shales at the base of a 50 m thick shelf margin deltaic sequence (Cummings and Arnott 2005) abruptly overlie the limestone. This is like a miniature version of the Abenaki carbonate platform terminations to the southwest and ignoring subsidence indicates an initial water depth around 50m. The change from microbialite up tosponge reef with possible red algae in a total of less than 5m indicates a relative sea-level fall and supports an interpreted forced regression. Like the modern Fraser delta sponge reefs, these more calcareous Jurassic sponge reefs were in deep quiet nutrient-rich waters but not yet engulfed and buried by clay sediment of an encroaching delta. Such a setting was environmentally untenable for shallow-water carbonate sedimentation that had therefore already "drowned".

CARBONATE AND SILICICLASTIC SEQUENCE STRATIGRAPHY- EXAMPLES FROM THE LATE JURASSIC ABENAKI LIMESTONE AND WEST VENTURE DELTAIC BEDS, OFFSHORE NOVA SCOTIA, CANADA

Eliuk, Leslie¹; Wach, Grant<sup>2

1</sup>Dalhousie University Earth Sciences Box 852 (Creighton St), Lunenburg , Nova Scotia, B0J 2C0, Canada; ²Earth Sciences Dept. Dalhousie University, Halifax , Nova Scotia, B3H 4H6, Canada

Relative to their occurrence in thick siliciclastic sections, thin carbonates show utility as sensitive indicators of the surrounding sand and shale sedimentation. When composed of in situ framebuilders (microbial and skeletal) as demonstrated by inter-growth position, bioerosion, associated submarine cements and marine geopetals, the carbonates are particularly helpful for environmental inferences. Within the Sable Island paleodelta, cores in Penobscot L-30 and South Venture C-62 show both dark colors and limited biotic diversity with microbial textures. The C-62 cores are particularly interesting because they provide an independent check on the shelf-margin delta model and sequence stratigraphic scenario previously presented by others for the Venture gas field. In less than 7 meters, facies and fauna in limestone change upward from a biotically depauperate marl to a microbial mud mound, which is succeeded by an argillaceous sponge-microsolenid coral reef mound with some stromatoporoids and possible red algae. The sequence is interpreted to reflect a forced regression and falling sea level. This closely supports the published deltaic sequence stratigraphy as long as it is appreciated that the "condensed limestone facies" is actually a distal composite, recording changes in sea level, nutrient supply, and ultimately sediment type that replaces the carbonate as the delta progrades. The maximum flooding surface (MFS) occurs during the microbial mound stage, below an abrupt lithologic change across a pyritized hardground which is overlain by laminated black shale. This placement of the MFS reflects problematic differences in sequence stratigraphic concepts of carbonates versus siliciclastics. Relative to understanding the Abenaki platform, the C-62 core provides insights into relationships seen only in cuttings and sidewall cores in Queensland M-88 which drilled the slope and basin facies immediately in front of the Deep Panuke (Abenaki reservoir) gas field. M-88 and C-62 may be potential links for correlating and dating the massive (Abenaki) carbonates and the deltaic siliciclastics.

CHARACTERIZATION OF PARALIC PALEOENVIRONMENTS USING BENTHIC FORAMINIFERA AND THECAMOEBIANS FROM EARLY CRETACEOUS SEDIMENTS (SCOTIAN SHELF)

Fiorini, Flavia 1¹; Wach, Grant D²; Scott, David B<sup>2

1</sup>1Smithsonian Tropical Research Institute, Ancon, Panama, none, Panama; ²5 Edsel dr, Halifax, Nova Scotia, B3H3J5, Canada

The benthic foraminifera and thecamoebians from an early Cretaceous cored interval of Cohasset A-52 well (located on the Scotian Shelf- North Atlantic), were used to interpret the depositional environments of these sediments. Paleoenvironmental interpretation was based on the analysis of samples from four cored intervals of A-52 corresponding to 25 m of interbedded, gray-black shale, mudstone and sandstone belonging to the Cree Member of the Logan Canyon Formation (Aptian –Albian). The foraminiferal association recovered from the samples is comprised mainly of agglutinated species of Trochammina, Haplophragmoides, Ammobaculites and Verneulinoides which are comparable at the generic level with the microfauna that live in modern marshes. A scattered occurrence of calcareous benthic foraminifera (typical of marginal marine environment) and thecamoebians (freshwater to brackish environment) is also recorded. The comparison of this microfauna with modern and fossil foraminiferal associations from paralic environment suggests that the sediments in the Cretaceous of A-52 were deposited in a marsh-estuarine environment. Additionally the species from A-52 were identical to those found in the Cretaceous of Alberta’s Bearpaw Fm.

RESERVOIR CONNECTIVITY ANALYSIS, HYDROCARBON DISTRIBUTION, RESOURCE POTENTIAL & PRODUCTION PERFORMANCE IN THE CLASTIC PLAYS OF THE SABLE SUBBASIN, SCOTIAN SHELF

Richards, Bill ¹; Fairchild, Lee H. ²; Vrolijk, Peter J. ³; Hippler, Susan J. <sup>4

1</sup> ExxonMobil Canada 1701 Hollis Street, P.O.Box 517, Halifax, Nova Scotia, B3J 3MB, Canada; ²Gorge Geotechnical, Parkdale, Hood River, Oregon, 97041, United States; ³ExxonMobil Upstream Research Company, P.O.Box 2189, Houston, Texas, 77098 , United States; ⁴ExxonMobil Exploration Company, 233 Benmar, Houston, Texas, 77060, United States

Reservoir Connectivity Analysis is a systematic approach to understanding reservoir "plumbing". It is based on well-known physical principles and is documented in a 2005 SPE paper (Vrolijk et al, SPE-93577-PP).

RCA is central to understanding fluids, pressures and field/pool size distribution in the clastic reservoirs of the Sable Subbasin. We will illustrate this approach with examples from the five producing Sable gas fields, other significant discoveries, and, the recent, third tranche of exploration and delineation drilling.

Hydrocarbon traps in the clastic system at Sable vary progressively from linear, low relief, extensional fault bend folds (which have small scale internal faulting), to high relief, heavily faulted domes where salt movement is involved in addition to listric faulting. It was recognized pre-production that despite complex overpressure distribution (attributed to recent charge) hydrocarbon accumulations are dominantly controlled geometrically, by "fill & spill" mechanisms: spill and breakovers at structural saddles, and critically, juxtapositional connections at internal and bounding faults. Because the Sable Subbasin is predominantly a high net-to-gross, marginal marine system with limited thick topseals there is - with a few very important exceptions - a propensity for "leaky traps", short hydrocarbon columns, and numerous small hydrocarbon pools.

In the absence of direct seismic indications of hydrocarbons, RCA has been the most effective technique for fluid prediction ahead of the drill. Previous speculation that fault processes and ensuing “fault rocks” would provide lateral seals, with longer gas columns and a larger resource is inconsistent with drilling results and production history.

GEOLOGICAL EVOLUTION AND HYDROCARBON POTENTIAL OF THE HATTON BASIN (UK SECTOR), NORTHEAST ATLANTIC OCEAN

McInroy, David Burns¹; Hitchen, Ken<sup>2

1</sup>British Geological Survey Murchison House, West Mains Road, Edinburgh, --, EH9 3LA, United Kingdom; ²Murchison House, West Mains Road, Edinburgh, --, EH9 3LA, United Kingdom

The deep-water Hatton Basin (flanked by the Hatton and Rockall Highs) is located 600km west of Scotland (NE Atlantic Ocean) on the western margin of the Eurasian continental plate. Prior to Atlantic opening, the area was adjacent to SE Greenland. The basin straddles the UK/Irish median line. Water depths increase southwards from 1000m to over 1300m.

The basin has never been licensed for hydrocarbon exploration and is currently the subject of ownership negotiations related to the UN Convention on Law of the Sea. Consequently it is under-explored. The deepest borehole penetration is by DSDP borehole 116 which terminated at 854m below sea bed in the Upper Eocene.

The Pre-Cambrian metamorphic basement only crops out on Rockall Bank where high-grade gneiss and granulite have been sampled and dated at c. 1900 to 1700 Ma. This is a different terrane from that which underlies most of Scotland. Palaeozoic rocks have not been proved in the area but may provide some of the pre-rift basin infill. The Hatton Basin probably opened during the Cretaceous. Recent (2007) seismic data suggest the presence of tilted fault blocks on the basin margins. Mid Cretaceous (Albian) sandstones and mudstones have been proved at shallow depth on the Hatton High. The area was affected by massive Late Paleocene to earliest Eocene volcanism which emplaced several large central igneous complexes and caused widespread lavas which degrade the seismic data from the deeper geology. Atlantic rifting commenced west of the Hatton High at about 56 Ma. During the Cenozoic the Hatton Basin was affected by differential subsidence and several unconformity-forming compressional events.

Numerous potential hydrocarbon trap styles have been identified including syn-rift tilted fault blocks, folds, truncations, prograding fans, pinch-outs, scarp fans and traps related to sill intrusions. Reservoir intervals are likely to be present in the Cretaceous, Paleocene and Eocene. The overlying Oligocene to Recent sediments are mudstones and oozes and may provide a seal. The main risks for an accumulation are the presence of a source rock and the shallow occurrence of some of the potential traps.

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STRUCTURE AND RIFTING EVOLUTION OF THE NORTHERN NEWFOUNDLAND BASIN FROM ERABLE MULTICHANNEL SEISMIC REFLECTION PROFILES ACROSS THE SOUTHERN MARGIN OF FLEMISH CAP

Welford, J. Kim¹; Smith, Julie ²; Hall, Jeremy²; Deemer, Sharon²; Srivastava, Shiri ³; Sibuet, Jean-Claude <sup>4

1</sup>Memorial University of Newfoundland 300 Prince Philip Drive, St. John’s, NL, A1B 3X5, Canada; ²300 Prince Philip Drive, St. John’s, NL, A1B 3X5, Canada; ³Geological Survey of Canada, Bedford Institute of Oceanography, P.O. Box 1006, Dartmouth, NS, B2Y 4A2, Canada; ⁴Ifremer, Centre de Brest, Département des Géosciences Marines, B.P. 70, 29280 Plouzané, France

We present four multichannel seismic reflection profiles from the 1992 ERABLE experiment collected over the southern margin of Flemish Cap and extending into the Newfoundland Basin. These profiles are between and sub-parallel to lines 1 and 2 from the 2000 SCREECH seismic experiment and provide more comprehensive data coverage over the region. Combining these data with the SCREECH seismic profiles, two ODP drill sites, and other geophysical data has allowed the mapping of distinct zones of continental, transitional, and oceanic crust in this region. Comparisons with mapped crustal boundaries on the Iberian margin from detailed seismic surveys and drilling show asymmetry in the conjugate pair, with the zone of extended continental crust and transitional crust being much wider on the Iberian margin compared to the Newfoundland margin. Furthermore, while detachment faulting is evidenced on both margins, it is less widespread on the Newfoundland margin. We propose either a simple shear or a simple shear/pure shear combination model involving a westward dipping detachment fault, with the Newfoundland margin acting as the upper plate. Along- margin variations in the present- day structure, which deviate from the simple 2-D rifting model, are explained within the context of Late Jurassic to Early Cretaceous rifting and break-up.

RESERVOIR QUALITY, DIAGENETIC HISTORY AND PROVENANCE OF THE LATE TRIASSIC SANDSTONES OF THE WOLFVILLE FORMATION, BAY OF FUNDY, NOVA SCOTIA, CANADA

Kettanah, Yawooz¹; Kettanah, Muhammad²; Wach, Grant <sup>2

1</sup>Dalhousie University Department of Earth Sciences, Halifax, Nova Scotia, B3H 4J1, Canada; ²Department of Earth Sciences, Halifax, Nova Scotia, B3H 4J1, Canada

The provenance of Triassic Wolfville Formation sandstones at Cambridge Cove, Bay of Fundy were investigated using petrography, heavy minerals, and microprobe analysis of tourmalines and garnets as provenance indicators. The study included grain size analysis, diagenesis, porosity, heavy mineral analysis and possible reservoir characteristics dependent on these properties.

These fluvial sandstones are calcite cement-supported feldspathic litharenites to lithic felsarenites. The sandstones have a recycled orogenic provenance derived from metasedimentary and granitic rocks postdating collision and from the early stages of rifting.

The Meguma, Horton and Windsor Groups, and the South Mountain Batholith, which were and still are, the dominant rock units in the area, are the main provenance of Wolfville Formation sediments. Minor contribution from Appalachian exposures north of the Bay of Fundy in New Brunswick, cannot be excluded. However, the absence of volcanics in the studied sediments minimizes that possibility.

The Wolfville Formation, which is overlain by the Blomidon Formation, has a limited exposure area relative to its wide subsurface extension beneath the Bay of Fundy. In this area, it is underlain by the Horton Bluff Formation in the Minas Basin area, and by the Meguma and/or Avalon Terranes in the southwestern parts of the region.

Wolfville sandstones have porosities ranging from 2.6 to 16.6% (averaging 6%). Consequently, in the subsurface (beneath the Bay of Fundy), the sandstones are potentially moderately good reservoir rocks. Hydrocarbon charge could occur where these sandstones overlie potential source rocks; e.g., the organic-rich shales of Horton Bluff Formation, or where overlain by or laterally equivalent to Mesozoic lacustrine shales.

BIOSTRATIGRAPHIC STUDY OF CENOZOIC STRATA OF THE GRAND BANKS, NEWFOUNDLAND

Skilliter, Deborah¹; Williams, G.L.²; Fensome, R.A.²; Guerstein, G.R.³; MacRae, R.A. ⁴; Wach, G.<sup>5

1</sup>Nova Scotia Museum 1747 Summer Street, Halifax, N.S., B3H 3A6 and Dalhousie University, Department of Earth Sciences, Halifax, NS, B3H 4R2 , Canada; ²Natural Resources Canada, Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, 1 Challenger Drive, P.O. Box 1006, Dartmouth, Nova Scotia , B2Y 4A2, Canada; ³Lab de Palinologia, Depart. de Geologia, Universidad Nacional del Sur, San Juan 670, 8000 Bahia Blanca, República Argentina, Argentina; ⁴Saint Mary’s University, Geology Department, 923 Robie Street, Halifax, Nova Scotia, B3H 3C3, Canada; ⁵Dalhousie University, Department of Earth Sciences, Halifax, N.S., B3H 4R2, Canada

The only extensively cored Cenozoic sections from offshore eastern Canada were recovered from a series of coreholes drilled in 1965 by Pan American Petroleum Corporation (now part of BP P.L.C.) and Imperial Oil Canada. The coreholes are from several basins, including the Scotian, Horseshoe, South Whale and Jeanne d’Arc. Previously, only preliminary palynological studies have been made on materials from the coreholes. The current study focuses on Corehole 16 from the southern Jeanne d’Arc Basin and Corehole 2 from Bear Ridge. Corehole 16 penetrates a broadly fining-upwards section through the Banquereau Formation, with excellent dinocyst recovery, spanning the middle Eocene through the middle Miocene. Preliminary results indicate that Corehole 2 represents a similar sequence through broadly fining-upwards strata in the Banquereau Formation, spanning the Late Eocene to Pleistocene. By incorporating pollen and spores with dinocysts, we plan to consolidate the taxonomy, develop detailed event biostratigraphy, interpret local paleoenvironments, and determine the prevalence and age of offshore currents, particularly the Proto-Gulf Stream. The results will provide new insights into the Cenozoic history of offshore eastern Canada, including an awareness of climate change during this time.

UNUSUAL JURASSIC CONDENSATE OF THE HUDSON CANYON AREA U.S. ATLANTIC

Sassen, Roger¹; Post, Paul<sup>1

1</sup> TexasA&M University 16017Woodlake Dr., College Station, TX, 77845, United States

The abstract for the meeting has already been submitted (several months ago) to Ms. Trudy Lewis and it was accepted. Please see the accepted text of the abstract.