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Impact of oil emplacement on diagenesis in Cretaceous oil sands

2017; Canadian Society of Petroleum Geologists; Volume: 65; Issue: 2 Linguagem: Francês

10.2113/gscpgbull.65.2.327

2368-0261

Timothy Bata, John Parnell, Nuhu K. Samaila, John Still, Jen Russel-Houston,

Geological Studies and Exploration

Research Article| June 01, 2017 Impact of oil emplacement on diagenesis in Cretaceous oil sands Timothy Bata; Timothy Bata Department of Applied Geology Abubakar Tafawa Balewa University Bauchi, Nigeria Search for other works by this author on: GSW Google Scholar John Parnell; John Parnell School of Geosciences University of Aberdeen United Kingdom AB24 3UE Search for other works by this author on: GSW Google Scholar Nuhu K. Samaila; Nuhu K. Samaila Department of Applied Geology Abubakar Tafawa Balewa University Bauchi, Nigeria Search for other works by this author on: GSW Google Scholar John Still John Still School of Geosciences University of Aberdeen United Kingdom AB24 3UE Search for other works by this author on: GSW Google Scholar Author and Article Information Timothy Bata Department of Applied Geology Abubakar Tafawa Balewa University Bauchi, Nigeria John Parnell School of Geosciences University of Aberdeen United Kingdom AB24 3UE Nuhu K. Samaila Department of Applied Geology Abubakar Tafawa Balewa University Bauchi, Nigeria John Still School of Geosciences University of Aberdeen United Kingdom AB24 3UE Publisher: Canadian Society of Petroleum Geologists Received: 20 Sep 2016 Accepted: 22 Mar 2017 First Online: 17 Nov 2017 Online Issn: 2368-0261 Print Issn: 0007-4802 Copyright © 2017, The Canadian Society of Petroleum Geologists Bulletin of Canadian Petroleum Geology (2017) 65 (2): 327–342. https://doi.org/10.2113/gscpgbull.65.2.327 Article history Received: 20 Sep 2016 Accepted: 22 Mar 2017 First Online: 17 Nov 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Timothy Bata, John Parnell, Nuhu K. Samaila, John Still; Impact of oil emplacement on diagenesis in Cretaceous oil sands. Bulletin of Canadian Petroleum Geology 2017;; 65 (2): 327–342. doi: https://doi.org/10.2113/gscpgbull.65.2.327 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of Canadian Petroleum Geology Search Advanced Search Abstract Seventeen thin sections of Cretaceous oil sands from the Neuquén Basin (Argentina), Sergipe-Alagoas Basin (Brazil), Western Canadian Sedimentary Basin (Canada), Junggar Basin (China), Lower Saxony Basin (Germany), Kangerlussuaq Basin (Greenland), Arabian Basin (Kuwait), Chad Basin (Nigeria), Dahomey Basin (Nigeria), Western Moray Firth Basin (UK), Wessex Basin (UK) and Utah (USA) were examined using the scanning electron microscope (SEM) to improve our understanding on how oil emplacement impairs the progress of diagenesis. Our results show that diagenetic processes affecting sandstones prior to oil emplacement include burial/compaction, silica/calcite cementation, calcite replacement of detrital grains/cements as well as the development of silica overgrowth. Most diagenetic processes were inferred to cease upon oil emplacement into the pores of the sandstones, however, diagenetic processes such as the alteration of detrital grains/cements and precipitation of authigenic minerals/metallic compounds were observed to occur after oil emplacement into the pores of the sandstones. Oil was emplaced in some of the studied Cretaceous oil sands at a relatively early stage when the sandstones were not compacted or cemented. Such Cretaceous oil sands were observed to have had anomalously high porosities of above 38% prior to oil emplacement. The only cement observed in these oil sands are the viscous heavy oils (bitumens) associated with them. Upon extraction of these heavy oils, the oil sands collapse into unconsolidated sands. Occurrence of these bitumen supported Cretaceous sands implies availability of migrating oils while some of the Cretaceous sands were depositing in various basins. Oil emplacement occurred in some of the studied Cretaceous oil sands after the sandstones had undergone some diagenetic processes which did not destroy all their pore spaces. Such Cretaceous oil sands were observed to have had moderate to high porosities of 10%–30% prior to oil emplacement, with some of these sandstones showing evidence of silica overgrowth. Emplacement of oil into the pores of such sandstones is believed to have stopped further development of the silica overgrowth that would have led to the total loss of porosity in these Cretaceous reservoir sands. In some of the studied Cretaceous oil sands, oil emplacement occurred when the sands had experienced a long history of diagenetic events leading to almost total loss of porosity. Common diagenetic features observed in such Cretaceous oil sands include sutured quartz grain-grain contacts and quartz overgrowth. Résumé Afin de mieux comprendre dans quelle mesure la mise en place du pétrole affecte la progression de la diagenèse, on a examiné, à l’aide du microscope à balayage électronique (MBE), dix-sept lames minces de sables bitumineux du Crétacé provenant des endroits suivants : bassin de Neuquén (Argentine), bassin de Sergipe-Alagoas (Brésil), bassin sédimentaire occidental canadien (Canada), bassin de Junggar (Chine), bassin de Basse-Saxe inférieur (Allemagne), bassin de Kangerlussuaq (Groenland), bassin de la mer d’Oman (KoweiÏt), bassin du lac Tchad (Nigéria), bassin du Dahomey (Nigéria), bassin occidental de Moray Firth (R.-U.), bassin de Wessex (R.-U.) et Utah (É.-U.). Nos résultats indiquent que les processus diagénétiques qui affectent le grès avant la mise en place du pétrole incluent l’enfouissement, la compaction, la cimentation silico-calcitique, le remplacement calcitique de grains et ciments détritiques, de même que l’accroissement secondaire de silice. On supposait que la plupart des processus diagénétiques devait cesser avec la mise en place du pétrole dans les pores du grès; après observations, cependant, les processus diagénétiques, en l’occurrence l’altération des grains et ciments détritiques, d’une part, et la précipitation de composés minéraux et métalliques authigènes, d’autre part, se produisaient après l’entrée du pétrole dans les pores du grès. Durant la période où le grès n’était ni compacté ni cimenté, le pétrole s’est mis en place dans certains sables bitumineux du Crétacé à un stade relativement précoce. Avant la mise en place du pétrole, de tels sables bitumineux du Crétacé avaient une porosité anomale supérieure a 38%. Le seul ciment observé dans ces sables pétrolifères était sous la forme de pétrole lourd visqueux (bitume) associé à celui-ci. Au cours de l’extraction de ces pétroles lourds, le sable bitumineux s’est effondré en sable non consolidé. L’existence de ces sables du Crétacé supportés par le bitume suppose la disponibilité du pétrole qui migre, tandis qu’une partie des sables du Crétacé se déposait ailleurs dans divers bassins. La mise en place du pétrole s’est produite dans certains sables bitumineux du Crétacé étudiés après que le grès ait été soumis a des processus diagénétiques lesquels n’ont pas détruit tous les interstices. De tels sables du Crétacé avaient des porosités allant de modérées a élevées soit de 10% à30 % avant la mise en place du pétrole, et certains des grès affichaient des indices d’accroissement secondaire de silice. On croit que la mise en place de pétrole dans les pores de ces grès aurait stoppé l’accroissement secondaire de silice, ce qui aurait mené a la perte totale de porosité dans les gisements pétrolifères du Crétacé. Dans certains des sables bitumineux du Crétacé étudiés, la mise en place du pétrole est arrivée lorsque les sables ont été soumis a un long épisode de diagenèse conduisant a une quasi-perte totale de porosité. Les caractéristiques diagénétiques communes remarquées dans les sables du Crétacé incluent des sutures de points de contact entre les grains et un accroissement secondaire de quartz.Michel Ory You do not have access to this content, please speak to your institutional administrator if you feel you should have access.