Pub Date : 2016-09-01DOI: 10.2113/GSCPGBULL.64.3.415
Liya Zhang, L. Buatois
The Upper Devonian–Lower Mississippian Bakken Formation in the subsurface of the Williston Basin in northeastern Montana, North Dakota, southwestern Manitoba and southern Saskatchewan typically includes three members: the lower and upper organic-rich black shale, and the middle calcareous/dolomitic sandstone and siltstone, which makes a “perfect” petroleum system including source rock, reservoir, and seal all within the same formation. In eastern Saskatchewan, the Bakken Formation is divided into eight facies, and one of which (Facies 2) is subdivided into two subfacies: Facies 1 (planar cross-stratified fine-grained sandstone); Facies 2A (wavy- to flaser-bedded very fine-grained sandstone); Facies 2B (thinly parallel-laminated very fine-grained sandstone and siltstone); Facies 3 (parallel-laminated very fine-grained sandstone and muddy siltstone); Facies 4 (sandy siltstone); Facies 5 (highly bioturbated interbedded very fine-grained sandstone and siltstone); Facies 6 (interbedded highly bioturbated sandy siltstone and micro-hummocky cross-stratified very fine-grained sandstone); Facies 7 (highly bioturbated siltstone); and Facies 8 (black shale). Our integrated sedimentologic and ichnologic study suggests that deposition of the Bakken occurred in two different paleoenvironmental settings: open marine (Facies 4 to 8) and brackish-water marginal marine (Facies 1 to 3). The open-marine facies association is characterized by the distal Cruziana Ichnofacies, whereas the brackish-water marginal-marine facies association is characterized by the depauperate Cruziana Ichnofacies. Isochore maps show that both open-marine and marginal-marine deposits are widely distributed in the study area and suggest the existence of a N-S trending paleo-shoreline. The Bakken strata in the study area represent two different transgressive systems tracts separated by a coplanar surface or amalgamated sequence boundary and transgressive surface. This surface has been identified in previous studies west-southwest of the study area, therefore assisting in high-resolution correlation of Bakken strata. The unusual stratigraphic architecture of the Bakken Formation in this area resulted from its proximal emplacement which favored intense erosion and cannibalization of previously accumulated deposits.
{"title":"Sedimentology, ichnology and sequence stratigraphy of the Upper Devonian–Lower Mississippian Bakken Formation in eastern Saskatchewan","authors":"Liya Zhang, L. Buatois","doi":"10.2113/GSCPGBULL.64.3.415","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.3.415","url":null,"abstract":"The Upper Devonian–Lower Mississippian Bakken Formation in the subsurface of the Williston Basin in northeastern Montana, North Dakota, southwestern Manitoba and southern Saskatchewan typically includes three members: the lower and upper organic-rich black shale, and the middle calcareous/dolomitic sandstone and siltstone, which makes a “perfect” petroleum system including source rock, reservoir, and seal all within the same formation. In eastern Saskatchewan, the Bakken Formation is divided into eight facies, and one of which (Facies 2) is subdivided into two subfacies: Facies 1 (planar cross-stratified fine-grained sandstone); Facies 2A (wavy- to flaser-bedded very fine-grained sandstone); Facies 2B (thinly parallel-laminated very fine-grained sandstone and siltstone); Facies 3 (parallel-laminated very fine-grained sandstone and muddy siltstone); Facies 4 (sandy siltstone); Facies 5 (highly bioturbated interbedded very fine-grained sandstone and siltstone); Facies 6 (interbedded highly bioturbated sandy siltstone and micro-hummocky cross-stratified very fine-grained sandstone); Facies 7 (highly bioturbated siltstone); and Facies 8 (black shale). Our integrated sedimentologic and ichnologic study suggests that deposition of the Bakken occurred in two different paleoenvironmental settings: open marine (Facies 4 to 8) and brackish-water marginal marine (Facies 1 to 3). The open-marine facies association is characterized by the distal Cruziana Ichnofacies, whereas the brackish-water marginal-marine facies association is characterized by the depauperate Cruziana Ichnofacies. Isochore maps show that both open-marine and marginal-marine deposits are widely distributed in the study area and suggest the existence of a N-S trending paleo-shoreline. The Bakken strata in the study area represent two different transgressive systems tracts separated by a coplanar surface or amalgamated sequence boundary and transgressive surface. This surface has been identified in previous studies west-southwest of the study area, therefore assisting in high-resolution correlation of Bakken strata. The unusual stratigraphic architecture of the Bakken Formation in this area resulted from its proximal emplacement which favored intense erosion and cannibalization of previously accumulated deposits.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.3.415","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68209453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-09-01DOI: 10.2113/GSCPGBULL.64.3.467
M. McMechan, W. Matthews, F. Ferri, B. Guest
Sandstone, shale and conglomerate of the Chinkeh Formation represent shoreface and channelized environments forming the base of the Cretaceous section in Liard Basin of northeast British Columbia, southeast Yukon and southwest Northwest Territories. Biostratigraphic constraints on the formation indicated a Hauterivian to Early Albian age. New U-Pb detrital zircon ages obtained from a subsurface core in the Maxhamish Lake area indicate a maximum depositional age of 112.6 ± 2.0 Ma and an Early Albian to latest Aptian age. Grain roundness and the diversity of zircon crystal morphologies suggest that most of the Cretaceous-aged zircons were derived from plutonic sources. Intrusions of the Anvil Suite, located approximately 550 km westnorthwest of the Maxhamish Lake area in the mid-Cretaceous, form the likely source. Erosion of the few kilometres of sediment originally overlying the intrusions would take at least a million years and plutonic zircon would not enter the sediment supply until then. Because of this delay in plutonic zircon availability, the new detrital zircon results suggest that the Chinkeh Formation in the Maxhamish Lake area is more likely Early Albian than latest Aptian in age, and support the Early Albian age assigned on the basis of foraminifera. Detrital zircon geochronology has proven to be a very useful tool in differentiating the Chinkeh Formation from similar Triassic strata.
{"title":"Maximum age of the basal Cretaceous Chinkeh Formation sandstones, Maxhamish Lake area, Liard Basin, British Columbia","authors":"M. McMechan, W. Matthews, F. Ferri, B. Guest","doi":"10.2113/GSCPGBULL.64.3.467","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.3.467","url":null,"abstract":"Sandstone, shale and conglomerate of the Chinkeh Formation represent shoreface and channelized environments forming the base of the Cretaceous section in Liard Basin of northeast British Columbia, southeast Yukon and southwest Northwest Territories. Biostratigraphic constraints on the formation indicated a Hauterivian to Early Albian age. New U-Pb detrital zircon ages obtained from a subsurface core in the Maxhamish Lake area indicate a maximum depositional age of 112.6 ± 2.0 Ma and an Early Albian to latest Aptian age. Grain roundness and the diversity of zircon crystal morphologies suggest that most of the Cretaceous-aged zircons were derived from plutonic sources. Intrusions of the Anvil Suite, located approximately 550 km westnorthwest of the Maxhamish Lake area in the mid-Cretaceous, form the likely source. Erosion of the few kilometres of sediment originally overlying the intrusions would take at least a million years and plutonic zircon would not enter the sediment supply until then. Because of this delay in plutonic zircon availability, the new detrital zircon results suggest that the Chinkeh Formation in the Maxhamish Lake area is more likely Early Albian than latest Aptian in age, and support the Early Albian age assigned on the basis of foraminifera. Detrital zircon geochronology has proven to be a very useful tool in differentiating the Chinkeh Formation from similar Triassic strata.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.3.467","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68209848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-09-01DOI: 10.2113/GSCPGBULL.64.3.438
G. F. Huff
There is a long and extensive history of study regarding the origins and characteristics of brines within the Alberta Basin of Canada. This study focuses on the origins of Li-enriched (>50 mg/kg) brines of the late Devonian Swan Hills, Nisku and Leduc Formations of the southwestern Alberta Basin. Available data show that two Li-enriched brines having distinctly different geochemical characteristics, and thus distinct evolutionary histories, exist within the late Devonian carbonates of the southwestern Alberta Basin. Li-enriched brine of the Swan Hills Formation appears to have been formed by dissolution of halite and mixing with Li-enriched fluids expelled from Precambrian crystalline basement. The degree of mixing between Swan Hills brines and meteoric water is unknown. Formation of Li-enriched brines in the Nisku and Leduc Formations could be explained by preferential dissolution of Li-enriched late-stage evaporite minerals, likely from the middle Devonian Prairie Evaporite Formation, into evapoconcentrated late Devonian seawater. Dense Li-enriched brine migrated downward into the underlying early Devonian Winnipegosis Formation and then westward in response to westward tilting beginning in Jurassic time. Li-enriched brine was then diluted by mixing with meteoric water driven into the Devonian of the southwestern Alberta Basin in response to hydraulic gradients created by the effects of Laramide tectonics.
{"title":"Evolution of Li-enriched oilfield brines in Devonian carbonates of the south-central Alberta Basin, Canada","authors":"G. F. Huff","doi":"10.2113/GSCPGBULL.64.3.438","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.3.438","url":null,"abstract":"There is a long and extensive history of study regarding the origins and characteristics of brines within the Alberta Basin of Canada. This study focuses on the origins of Li-enriched (>50 mg/kg) brines of the late Devonian Swan Hills, Nisku and Leduc Formations of the southwestern Alberta Basin. Available data show that two Li-enriched brines having distinctly different geochemical characteristics, and thus distinct evolutionary histories, exist within the late Devonian carbonates of the southwestern Alberta Basin.\u0000\u0000Li-enriched brine of the Swan Hills Formation appears to have been formed by dissolution of halite and mixing with Li-enriched fluids expelled from Precambrian crystalline basement. The degree of mixing between Swan Hills brines and meteoric water is unknown.\u0000\u0000Formation of Li-enriched brines in the Nisku and Leduc Formations could be explained by preferential dissolution of Li-enriched late-stage evaporite minerals, likely from the middle Devonian Prairie Evaporite Formation, into evapoconcentrated late Devonian seawater. Dense Li-enriched brine migrated downward into the underlying early Devonian Winnipegosis Formation and then westward in response to westward tilting beginning in Jurassic time. Li-enriched brine was then diluted by mixing with meteoric water driven into the Devonian of the southwestern Alberta Basin in response to hydraulic gradients created by the effects of Laramide tectonics.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.3.438","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68209605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.166
M. Barton
Abstract This study focuses on the stratigraphy and internal architecture within the middle/upper portion of the McMurray Formation as seen at the Shell Albian Sands Lease (Rge 10W4M and Rge 9W4M along Twp 95), NE Alberta. Based on facies patterns and stratal relationships mapped from borehole data and mine exposures a number of conclusions can be made regarding architecture of the middle-to-upper McMurray including: 1) the informal subdivision of the McMurray into middle and upper units, 2) general environments of deposition, 3) the character of the stratigraphic framework, 4) the inferred accommodation setting. Key findings of this work include the following: Subdivision of the McMurray Formation into middle and upper units based on upward change from inclined estuarine strata to flat bedded nearshore marine and coastal plain strata is feasible through much of the study area. However, the boundary displays considerable complexity and is not characterized by a single stratigraphic surface or contact that can be correlated across the study area. Facies and bedding characteristics indicate a significant portion of the IHS was deposited by tidal bars rather than tidal-fluvial point bars as most previous studies assigned the facies to. The middle-to-upper McMurray section is subdivided by a series of high relief unconformities. The morphology of the unconformities suggests they are erosional valleys filled with a transgressive succession of facies that ranges from fluvial or inner estuarine at the base to outer estuarine or nearshore marine at the top. Estuarine and nearshore marine strata within the valley fills show considerable variation in the amount of tide versus wave influence. Initial valley fills are tide-influenced whereas later valley fills show a progressive increase in wave influence. The progressive change in tide versus wave influence is interpreted to reflect a change in shoreline morphology from an initial shoreline setting that was highly embayed to a final shoreline setting that was linear to weakly embayed. The middle-to-upper McMurray largely fills in accommodation space created by changes in relative sea level. Structural subsidence associated with the dissolution of the Prairie Evaporite was likely occurring but to a lesser extent than with the lower McMurray. As a result, stratal relationships within the middle-to-upper McMurray are relatively flat and not strongly correlated with relief on the Pre-Cretaceous unconformity. The stratigraphic architecture of the contrasts sharply with the lower McMurray where widespread unconformities are not observed and facies patterns are controlled by subsidence patterns related to dissolution and collapse of the underlying Devonian Prairie Evaporite.
{"title":"The architecture and variability of valley-fill deposits within the Cretaceous McMurray Formation, Shell Albian Sands Lease, northeast Alberta","authors":"M. Barton","doi":"10.2113/GSCPGBULL.64.2.166","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.166","url":null,"abstract":"Abstract This study focuses on the stratigraphy and internal architecture within the middle/upper portion of the McMurray Formation as seen at the Shell Albian Sands Lease (Rge 10W4M and Rge 9W4M along Twp 95), NE Alberta. Based on facies patterns and stratal relationships mapped from borehole data and mine exposures a number of conclusions can be made regarding architecture of the middle-to-upper McMurray including: 1) the informal subdivision of the McMurray into middle and upper units, 2) general environments of deposition, 3) the character of the stratigraphic framework, 4) the inferred accommodation setting. Key findings of this work include the following: Subdivision of the McMurray Formation into middle and upper units based on upward change from inclined estuarine strata to flat bedded nearshore marine and coastal plain strata is feasible through much of the study area. However, the boundary displays considerable complexity and is not characterized by a single stratigraphic surface or contact that can be correlated across the study area. Facies and bedding characteristics indicate a significant portion of the IHS was deposited by tidal bars rather than tidal-fluvial point bars as most previous studies assigned the facies to. The middle-to-upper McMurray section is subdivided by a series of high relief unconformities. The morphology of the unconformities suggests they are erosional valleys filled with a transgressive succession of facies that ranges from fluvial or inner estuarine at the base to outer estuarine or nearshore marine at the top. Estuarine and nearshore marine strata within the valley fills show considerable variation in the amount of tide versus wave influence. Initial valley fills are tide-influenced whereas later valley fills show a progressive increase in wave influence. The progressive change in tide versus wave influence is interpreted to reflect a change in shoreline morphology from an initial shoreline setting that was highly embayed to a final shoreline setting that was linear to weakly embayed. The middle-to-upper McMurray largely fills in accommodation space created by changes in relative sea level. Structural subsidence associated with the dissolution of the Prairie Evaporite was likely occurring but to a lesser extent than with the lower McMurray. As a result, stratal relationships within the middle-to-upper McMurray are relatively flat and not strongly correlated with relief on the Pre-Cretaceous unconformity. The stratigraphic architecture of the contrasts sharply with the lower McMurray where widespread unconformities are not observed and facies patterns are controlled by subsidence patterns related to dissolution and collapse of the underlying Devonian Prairie Evaporite.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.2.166","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68208430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.218
B. Harris, E. Timmer, M. Ranger, M. Gingras
Abstract The McMurray Formation comprises fluvial, estuary, delta and embayment deposits, for which the ichnology is well studied. Workers have recognized the dominantly brackish-water character of trace-fossil assemblages and those studies have contributed heavily to the interpretation of the deposit. This study considers the significance of lower McMurray Formation strata that contain a continental trace fossil assemblage. The studied outcrops comprise a coarse-grained sandstone channel that overlies and crosscuts large-scale, unidirectionally-dipping, interbedded, finegrained sandstone and minor siltstone (i.e. Inclined Heterolithic Stratification referred to henceforth as IHS). Both lithofacies are overlain by a pedogenically altered clayey siltstone. The coarse-grained channel contains oriented wood clasts, and lacks bioturbation. The cross-cut IHS is devoid of large wood clasts and is commonly bioturbated. The IHS locally displays beds of granular sandstone that are lithologically similar to the channel sandstones. The IHS-associated trace fossil assemblage is composed of a range of forms that hitherto now, have not been formally reported from the McMurray Formation. Trace fossils that contain irregular back-fill and burrow diameters, as well as varying orientations, are assigned to a range of adhesive meniscate backfilled burrows, including the ichnogenus Naktodemasis and Taenidium. Collectively, these trace fossils are associated with insect larvae and are taken as indicators of freshwater sedimentation. Other trace fossils, such as Siphonichnus and Cylindrichnus, are interpreted to be associated with low-salinity waters: as such the outcrops most likely represent sedimentation in the innermost estuary, with the coarse-grained channel representing a cross-cutting fluvial deposit. The fresh-water and low-salinity trace fossil assemblage has not previously been described in the McMurray Formation. Importantly, the presence of continental and brackish-water trace fossils together offers a perspective of this McMurray locale. Lithologically, the fluvial and estuary deposits are clearly discernible.
{"title":"Continental ichnology of the Lower McMurray Formation inclined heterolithic strata at Daphne Island, Athabasca River, north-eastern Alberta, Canada","authors":"B. Harris, E. Timmer, M. Ranger, M. Gingras","doi":"10.2113/GSCPGBULL.64.2.218","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.218","url":null,"abstract":"Abstract The McMurray Formation comprises fluvial, estuary, delta and embayment deposits, for which the ichnology is well studied. Workers have recognized the dominantly brackish-water character of trace-fossil assemblages and those studies have contributed heavily to the interpretation of the deposit. This study considers the significance of lower McMurray Formation strata that contain a continental trace fossil assemblage. The studied outcrops comprise a coarse-grained sandstone channel that overlies and crosscuts large-scale, unidirectionally-dipping, interbedded, finegrained sandstone and minor siltstone (i.e. Inclined Heterolithic Stratification referred to henceforth as IHS). Both lithofacies are overlain by a pedogenically altered clayey siltstone. The coarse-grained channel contains oriented wood clasts, and lacks bioturbation. The cross-cut IHS is devoid of large wood clasts and is commonly bioturbated. The IHS locally displays beds of granular sandstone that are lithologically similar to the channel sandstones. The IHS-associated trace fossil assemblage is composed of a range of forms that hitherto now, have not been formally reported from the McMurray Formation. Trace fossils that contain irregular back-fill and burrow diameters, as well as varying orientations, are assigned to a range of adhesive meniscate backfilled burrows, including the ichnogenus Naktodemasis and Taenidium. Collectively, these trace fossils are associated with insect larvae and are taken as indicators of freshwater sedimentation. Other trace fossils, such as Siphonichnus and Cylindrichnus, are interpreted to be associated with low-salinity waters: as such the outcrops most likely represent sedimentation in the innermost estuary, with the coarse-grained channel representing a cross-cutting fluvial deposit. The fresh-water and low-salinity trace fossil assemblage has not previously been described in the McMurray Formation. Importantly, the presence of continental and brackish-water trace fossils together offers a perspective of this McMurray locale. Lithologically, the fluvial and estuary deposits are clearly discernible.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.2.218","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68208634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.106
Timothy P. Bata, J. Parnell, S. Bowden, A. Boyce
Abstract Much of the world’s heavy oil is found in Cretaceous reservoir rocks due to a combination of tectonic, climatic, geological, and biological factors. Here we study Cretaceous oil sands from the Neuquen Basin (Argentina), Sergipe-Alagoas Basin (Brazil), Alberta (Canada), Dahomey Basin (Nigeria), Uinta Basin (USA), Western Moray Firth Basin (United Kingdom), and Wessex Basin (United Kingdom) to improve our understanding of the origin of the heavy oils. Our results indicate that the oils were generated as conventional light oil, which later degraded into heavy oils, rather than thermally cracked oils from over matured source rocks. All the studied Cretaceous oil sands are enriched in the polar fraction, and the total ion current (TIC) fragmentogram of the saturate fractions show unresolved complex mixture (UCM) humps indicating that the oils have undergone biodegradation. Sterane data for the Cretaceous oil sands show a selective increase in the C29 regular steranes relative to C27 and C28 regular sterane, which is also consistent with biodegradation. There is also evidence for diasterane degradation in some samples which are related, suggesting severe biodegradation. The trisnorhopane thermal maturity indicator showed that the Cretaceous oil sands have thermal maturity levels equivalent to 0.66–1.32% Ro, consistent with an early to late oil window. 25-norhopanes were not detected in any of the studied Cretaceous oil sands despite sterane degradation. This strongly suggests that biodegradation in the Cretaceous oil sands occurred at shallow depths rather than at greater depths. Pyrite associated with the Cretaceous oil sands was found to be consistently isotopically light. The isotopic fractionation between these pyrites and contemporary seawater sulfate was calculated using the mean δ34S values and the established seawater composition curve. This fractionation exceeded the maximum known kinetic isotope fractionation of approximately 20‰ that is possible from non-biogenic mechanisms, such as thermochemical sulfate reduction. This strongly suggests that the pyrite precipitated from an open system by means of microbial sulfate reduction as part of the biodegradation process.
{"title":"Origin of heavy oil in Cretaceous petroleum reservoirs","authors":"Timothy P. Bata, J. Parnell, S. Bowden, A. Boyce","doi":"10.2113/GSCPGBULL.64.2.106","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.106","url":null,"abstract":"Abstract Much of the world’s heavy oil is found in Cretaceous reservoir rocks due to a combination of tectonic, climatic, geological, and biological factors. Here we study Cretaceous oil sands from the Neuquen Basin (Argentina), Sergipe-Alagoas Basin (Brazil), Alberta (Canada), Dahomey Basin (Nigeria), Uinta Basin (USA), Western Moray Firth Basin (United Kingdom), and Wessex Basin (United Kingdom) to improve our understanding of the origin of the heavy oils. Our results indicate that the oils were generated as conventional light oil, which later degraded into heavy oils, rather than thermally cracked oils from over matured source rocks. All the studied Cretaceous oil sands are enriched in the polar fraction, and the total ion current (TIC) fragmentogram of the saturate fractions show unresolved complex mixture (UCM) humps indicating that the oils have undergone biodegradation. Sterane data for the Cretaceous oil sands show a selective increase in the C29 regular steranes relative to C27 and C28 regular sterane, which is also consistent with biodegradation. There is also evidence for diasterane degradation in some samples which are related, suggesting severe biodegradation. The trisnorhopane thermal maturity indicator showed that the Cretaceous oil sands have thermal maturity levels equivalent to 0.66–1.32% Ro, consistent with an early to late oil window. 25-norhopanes were not detected in any of the studied Cretaceous oil sands despite sterane degradation. This strongly suggests that biodegradation in the Cretaceous oil sands occurred at shallow depths rather than at greater depths. Pyrite associated with the Cretaceous oil sands was found to be consistently isotopically light. The isotopic fractionation between these pyrites and contemporary seawater sulfate was calculated using the mean δ34S values and the established seawater composition curve. This fractionation exceeded the maximum known kinetic isotope fractionation of approximately 20‰ that is possible from non-biogenic mechanisms, such as thermochemical sulfate reduction. This strongly suggests that the pyrite precipitated from an open system by means of microbial sulfate reduction as part of the biodegradation process.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.2.106","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68208686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.309
G. Prost, J. Newsome
Abstract The Cenovus-ConocoPhillips Christina Lake oilsands project uses Steam-Assisted Gravity Drainage (SAGD) to recover bitumen from the Lower Cretaceous McMurray Formation at depths between 300 and 400 m. The McMurray Formation at the Christina Lake Field consists of fluvial to estuarine sands and muds capped by marine shales and sands of the Wabiskaw member of the Clearwater Formation. The SAGD process involves injecting steam under pressure to mobilize the bitumen, which is then pumped to the surface. The increased reservoir pressure is expected to be contained by the caprock. In the event of a failure of the caprock to contain these pressures the steam and oil may escape to shallower units and possibly the surface. This is not a desired outcome. We describe a process to characterize overburden and evaluate caprock strength. The minimum in situ principal stress is shown to be five times reservoir operating pressure and 2.5 times startup pressure. Compressive strength at the reservoir confining pressure of 4.5 MPa is six times operating pressure and three times startup pressure. The Wabiskaw member is shown to contain laterally continuous and impermeable semiconsolidated muds. Porosities and permeabilities are low and capillary entry pressure is high. A program of subsurface and surface monitoring is described.
Cenovus-ConocoPhillips Christina Lake油砂项目采用蒸汽辅助重力排水(SAGD)技术，在300 ~ 400米深度的McMurray组开采沥青。克里斯蒂娜湖油田的麦克默里组由河流到河口的砂和泥组成，上面覆盖着清水组瓦比斯考成员的海洋页岩和砂。SAGD过程包括在压力下注入蒸汽以调动沥青，然后将沥青泵送到地面。预计增加的储层压力将被盖层所控制。如果盖层无法控制这些压力，蒸汽和石油可能会泄漏到较浅的单元，甚至可能会泄漏到地面。这不是一个理想的结果。我们描述了一个过程来表征覆盖层和评价盖层强度。最小原位主应力为油藏工作压力的5倍，启动压力的2.5倍。油藏围压为4.5 MPa时的抗压强度为操作压力的6倍，启动压力的3倍。wabisow成员显示包含横向连续和不渗透的半固化泥浆。孔隙度和渗透率低，毛管进入压力高。介绍了一种地下和地表监测程序。
{"title":"Caprock integrity determination at the Christina Lake Thermal Recovery Project, Alberta","authors":"G. Prost, J. Newsome","doi":"10.2113/GSCPGBULL.64.2.309","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.309","url":null,"abstract":"Abstract The Cenovus-ConocoPhillips Christina Lake oilsands project uses Steam-Assisted Gravity Drainage (SAGD) to recover bitumen from the Lower Cretaceous McMurray Formation at depths between 300 and 400 m. The McMurray Formation at the Christina Lake Field consists of fluvial to estuarine sands and muds capped by marine shales and sands of the Wabiskaw member of the Clearwater Formation. The SAGD process involves injecting steam under pressure to mobilize the bitumen, which is then pumped to the surface. The increased reservoir pressure is expected to be contained by the caprock. In the event of a failure of the caprock to contain these pressures the steam and oil may escape to shallower units and possibly the surface. This is not a desired outcome. We describe a process to characterize overburden and evaluate caprock strength. The minimum in situ principal stress is shown to be five times reservoir operating pressure and 2.5 times startup pressure. Compressive strength at the reservoir confining pressure of 4.5 MPa is six times operating pressure and three times startup pressure. The Wabiskaw member is shown to contain laterally continuous and impermeable semiconsolidated muds. Porosities and permeabilities are low and capillary entry pressure is high. A program of subsurface and surface monitoring is described.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.2.309","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68209176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.99
F. Hein, K. Parks, D. Leckie, C. Seibel
This Special Issue of the Bulletin of Canadian Petroleum Geology grew out of a 3-day symposium on oil sands and heavy-oil co-sponsored by the Canadian Society of Petroleum Geologists (CSPG), the Energy Minerals Division (EMD) of the American Association of Petroleum Geologists (AAPG), and the AAPG. This symposium, entitled “Oil Sands and Heavy-Oil Symposium: Local to Global Multidisciplinary Collaboration,” was held October, 2014, in Calgary, AB, Canada. The main goals of the symposium were three-fold: 1. to highlight the global nature of the oil sands and heavy-oil resources; 2. to present and review the contributions resource geoscientists are making to the understanding of hydrocarbon emplacement and evolution; reservoir geology and characterization; along with the subsurface challenges of environmental protection, social license, and sustainable energy-development; and, 3. to discuss advances and challenges in recovery and remediation technologies. The originality, complexity, and breadth of ideas and results presented at the symposium warranted further documentation, discussion, and dissemination in the public domain. For this reason, the organizers of this symposium approached the CSPG Editorial Board to publish a special issue on many of the papers presented at the symposium, among others. Now, nearly 2 years later, the result is this volume, which has a wide-range of interests and issues, and keeps with the original multidisciplinary scope of the symposium. The present special volume is arranged according to the main goals and solicited submissions that came out of the symposium. The themes fall under three main categories: 1. basic reservoir characterization and understanding of bitumen-and heavy-oil resources; 2. advances in reservoir-characterization and recovery technologies; 3. geoscience contributions and issues regarding sustainable development. As a preface to the volume, it is requisite to discuss the magnitude and global nature of oil sands and heavy-oil resources. This topic was covered as a session in the original symposium, but no papers were submitted. …
{"title":"Foreword — Oil-sands and heavy-oil deposits: Local to global multidisciplinary collaboration","authors":"F. Hein, K. Parks, D. Leckie, C. Seibel","doi":"10.2113/GSCPGBULL.64.2.99","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.99","url":null,"abstract":"This Special Issue of the Bulletin of Canadian Petroleum Geology grew out of a 3-day symposium on oil sands and heavy-oil co-sponsored by the Canadian Society of Petroleum Geologists (CSPG), the Energy Minerals Division (EMD) of the American Association of Petroleum Geologists (AAPG), and the AAPG. This symposium, entitled “Oil Sands and Heavy-Oil Symposium: Local to Global Multidisciplinary Collaboration,” was held October, 2014, in Calgary, AB, Canada.\u0000\u0000The main goals of the symposium were three-fold: \u0000\u00001. to highlight the global nature of the oil sands and heavy-oil resources;\u0000\u00002. to present and review the contributions resource geoscientists are making to the understanding of hydrocarbon emplacement and evolution; reservoir geology and characterization; along with the subsurface challenges of environmental protection, social license, and sustainable energy-development; and,\u0000\u00003. to discuss advances and challenges in recovery and remediation technologies.\u0000\u0000The originality, complexity, and breadth of ideas and results presented at the symposium warranted further documentation, discussion, and dissemination in the public domain. For this reason, the organizers of this symposium approached the CSPG Editorial Board to publish a special issue on many of the papers presented at the symposium, among others. Now, nearly 2 years later, the result is this volume, which has a wide-range of interests and issues, and keeps with the original multidisciplinary scope of the symposium.\u0000\u0000The present special volume is arranged according to the main goals and solicited submissions that came out of the symposium. The themes fall under three main categories: \u0000\u00001. basic reservoir characterization and understanding of bitumen-and heavy-oil resources;\u0000\u00002. advances in reservoir-characterization and recovery technologies;\u0000\u00003. geoscience contributions and issues regarding sustainable development.\u0000\u0000As a preface to the volume, it is requisite to discuss the magnitude and global nature of oil sands and heavy-oil resources. This topic was covered as a session in the original symposium, but no papers were submitted. …","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.2.99","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68209482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.199
E. Timmer, M. Gingras, M. L. Morin, M. Ranger, J. Zonneveld
Abstract Inclined Heterolithic Stratification, characterized by dipping, interbedded and interlaminated sandstone and mudstone lithosomes comprises a major portion of the Athabasca Oil Sands. Fluvial processes have generally been interpreted to be the major cause of lithological variations and accompanying cyclicity in Inclined Heterolithic Stratification. The objectives of this research are applying quantitative and visual frequency analysis techniques, to determine and interpret the laminae-scale cyclicity of Inclined Heterolithic Stratification lithosomes. The Inclined Heterolithic Stratification in the Pierre River area is subdivided into five lithosomes based on distinct ichnological and sedimentological features. For each lithosome, Continuous Wavelet Transforms, applied to measurements of laminae or bed thicknesses, treated as pseudo time-series, converts these time-series to the frequency domain in order to determine the cyclicity of interlaminated portions of lithosomes. Visual identification of cycle breaks, by splitting series into cycles following troughs and peaks is completed as well. The results from the analysis demonstrate that the interlaminated portions of Inclined Heterolithic Stratification in the Pierre River Area preserve cyclic patterns that are consistent with semidiurnal synodic neap-spring tidal periodicity. Even in bioturbated intervals, interlaminated sandstone and mudstone is indicative of tidal cyclicity. The thicker sandstone or mudstone beds disrupting the tidally interlaminated portions of Inclined Heterolithic Stratification are interpreted to reflect variations in fluvial flux. This study gives a better understanding of the tidal regime during the lower Cretaceous McMurray Formation deposition and of the processes governing Inclined Heterolithic Stratification laminae-scale lithological variability.
{"title":"Laminae-scale rhythmicity of inclined heterolithic stratification, Lower Cretaceous McMurray Formation, NE Alberta, Canada","authors":"E. Timmer, M. Gingras, M. L. Morin, M. Ranger, J. Zonneveld","doi":"10.2113/GSCPGBULL.64.2.199","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.199","url":null,"abstract":"Abstract Inclined Heterolithic Stratification, characterized by dipping, interbedded and interlaminated sandstone and mudstone lithosomes comprises a major portion of the Athabasca Oil Sands. Fluvial processes have generally been interpreted to be the major cause of lithological variations and accompanying cyclicity in Inclined Heterolithic Stratification. The objectives of this research are applying quantitative and visual frequency analysis techniques, to determine and interpret the laminae-scale cyclicity of Inclined Heterolithic Stratification lithosomes. The Inclined Heterolithic Stratification in the Pierre River area is subdivided into five lithosomes based on distinct ichnological and sedimentological features. For each lithosome, Continuous Wavelet Transforms, applied to measurements of laminae or bed thicknesses, treated as pseudo time-series, converts these time-series to the frequency domain in order to determine the cyclicity of interlaminated portions of lithosomes. Visual identification of cycle breaks, by splitting series into cycles following troughs and peaks is completed as well. The results from the analysis demonstrate that the interlaminated portions of Inclined Heterolithic Stratification in the Pierre River Area preserve cyclic patterns that are consistent with semidiurnal synodic neap-spring tidal periodicity. Even in bioturbated intervals, interlaminated sandstone and mudstone is indicative of tidal cyclicity. The thicker sandstone or mudstone beds disrupting the tidally interlaminated portions of Inclined Heterolithic Stratification are interpreted to reflect variations in fluvial flux. This study gives a better understanding of the tidal regime during the lower Cretaceous McMurray Formation deposition and of the processes governing Inclined Heterolithic Stratification laminae-scale lithological variability.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2113/GSCPGBULL.64.2.199","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68208511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-06-01DOI: 10.2113/GSCPGBULL.64.2.251
E. Timmer, Scott E. Botterill, M. Gingras, J. Zonneveld
Abstract Process ichnology emphasizes the use of trace fossils as proxies for sedimentary processes and conditions. The advantage of this method is that depositional stresses can be identified based on several process-ichnological parameters. The purpose of this paper is to demonstrate the use of process-ichnology data, with a focus of establishing how process ichnology metrics can be visualized with geomodeling to aid spatial interpretation. For this study, process ichnology metrics (including bioturbation index and size diversity index), which is the product of interval ichnogenera diversity and interval maximum burrow diameter, are presented from a core dataset of the Cretaceous McMurray Formation. These data are modeled using standard geostastistical techniques for effective visualization of spatial trends. The modeled ichnology data are compared to sedimentary facies in order to interpret the dominant stresses occurring at the time of infaunal colonization. Several interpretations are made from the process ichnology model. The size diversity index and bioturbation index values from inclined heterolithic stratification show strong spatial variability related to variable depositional conditions across and along inclined heterolithic stratification bar forms. Facies interpreted to represent tidal flat deposition are distinguishable on the basis of relatively high bioturbation index values coupled with intermediate to low size diversity index values. Overall, we interpret variability in salinity and sedimentation rates to be the dominant infaunal stresses in the studied stratigraphic interval.
{"title":"Visualizing a process ichnology dataset, Lower Cretaceous McMurray Formation, NE Alberta, Canada","authors":"E. Timmer, Scott E. Botterill, M. Gingras, J. Zonneveld","doi":"10.2113/GSCPGBULL.64.2.251","DOIUrl":"https://doi.org/10.2113/GSCPGBULL.64.2.251","url":null,"abstract":"Abstract Process ichnology emphasizes the use of trace fossils as proxies for sedimentary processes and conditions. The advantage of this method is that depositional stresses can be identified based on several process-ichnological parameters. The purpose of this paper is to demonstrate the use of process-ichnology data, with a focus of establishing how process ichnology metrics can be visualized with geomodeling to aid spatial interpretation. For this study, process ichnology metrics (including bioturbation index and size diversity index), which is the product of interval ichnogenera diversity and interval maximum burrow diameter, are presented from a core dataset of the Cretaceous McMurray Formation. These data are modeled using standard geostastistical techniques for effective visualization of spatial trends. The modeled ichnology data are compared to sedimentary facies in order to interpret the dominant stresses occurring at the time of infaunal colonization. Several interpretations are made from the process ichnology model. The size diversity index and bioturbation index values from inclined heterolithic stratification show strong spatial variability related to variable depositional conditions across and along inclined heterolithic stratification bar forms. Facies interpreted to represent tidal flat deposition are distinguishable on the basis of relatively high bioturbation index values coupled with intermediate to low size diversity index values. Overall, we interpret variability in salinity and sedimentation rates to be the dominant infaunal stresses in the studied stratigraphic interval.","PeriodicalId":56325,"journal":{"name":"Bullentin of Canadian Petroleum Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2016-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68209066","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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