Evaluation of bitumen as a 187Re–187Os geochronometer for hydrocarbon maturation and migration: A test case from the Polaris MVT deposit, Canada (original) (raw)
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Chemical Geology, 1991
Parnell, J., Robinson, N. and Brassell, S., 1991. Discrimination of bitumen sources in Precambrian and Lower Palaeozoic rocks, southern U.K., by gas chromatography-mass spectrometry. Chem. Geol., 90: 1-14.
Natural Resources Research, 2007
The platform carbonates of the Upper Devonian Grosmont Formation hold an estimated 50 billion m 3 of bitumen in place and therefore host a significant amount (one-sixth) of the total bitumen resources in northern Alberta. However, unlike the overlying Athabasca oil sands, the bitumen resource has not been tapped as yet. The present study is an overview and integration of recent subsurface studies, largely focused along the eastern subsurface erosional edge of the Winterburn Group in northern Alberta. The basis of the regional geologic framework includes a detailed study of 42 cores with an emphasis on facies description of both reservoir and nonreservoir facies, and the summary of a diagenetic sequence model to demonstrate the major influences on bitumen accumulation. The Grosmont Formation carbonates have been subject to various stages of diagenesis, including dolomitization and karstification with a profound effect on the distribution of porosity and permeability, which resulted in highly heterogeneous reservoirs. In addition, low effective permeabilities because of high bitumen saturation, the high viscosity of the heavily biodegraded bitumen, and the continuity and integrity of shales capping bitumen-bearing reservoir facies are further factors that must be considered in applying future in-situ recovery schemes to the Grosmont carbonate bitumen deposit.
Marine and Petroleum Geology, 2010
The petroleum charge history of the Barrandian basin was investigated by analysing quartz and calcite and organic phases that occur in veins and fractures cutting dolerite sills within the Liteň Formation (Silurian). The geochemical characteristics of fluid inclusions trapped in vein quartz and calcite, vein bitumens and adjacent potential source rocks when combined with burial and thermal history data reflect the presence of at least three separate hydrocarbon charge episodes. Solid highly reflecting (R max ¼ 0.92-1.49%) bitumen provides information on the first and oldest episode of oil migration. The precursor oil was probably derived relatively early during diagenesis from nearby organic-rich sediments and was subsequently thermally altered to form the solid bitumen.
Bulletin of Canadian Petroleum Geology, 2001
The northeastern GaspE Peninsula is divided into two distinct tectono-stratigraphic domains: Cambro-Ordovician rocks of the Humber and Dunnage zones, to the north, and Siluro-Devonian rocks of the GaspE Belt, to the south. The northeastern part of the GaspE Belt is being investigated for its hydrocarbon potential. This area is dissected by major NW-trending faults that divide the study area into three tectonic domains: the northern, central and southern blocks. During the Late Silurian-Early Devonian Salinic disturbance, the faults were active as synsedimentary normal faults. Faults were reactivated as dextral strike-slip faults during the Middle Devonian Acadian Orogeny. Regional Acadian folds are ENE-to E-trending. Locally, NW-trending folds related to the Salinic disturbance occur close to the faults. Because of their total organic carbon content (TOC), the Cambro-Ordovician rocks were considered to be more likely source rocks than rocks of the Siluro-Devonian Gaspd Belt before maturation. Good source rock intervals are locally present in the York River Formation, in all the tectonic blocks of the study area. These beds are rich in organic matter, are marginally mature and of limited extent. Based on TOC and Rock-Eval analyses, the Indian Point and Forillon formations show significant thicknesses of fair source rocks in some wells of the central block where most oil indications and seeps occur. Our results indicate that these source rocks have the highest hydrocarbon potential. A new calibration is proposed between the reflectance of collotelinite (standard vitrinite) and that of chitinozoans and solid bitumen, which are more common than vitrinite in marine successions of the GaspE Belt. Interpretation of reflectance analysis indicates that thermal maturation in the GaspE Belt succession is primarily related to burial and occurred during deposition of the GaspE Sandstones. Maximum burial is contemporaneous with Acadian ENE-to Etrending folding and pre-dates strike-slip faulting. Oil and condensate in Indian Point and Forillon formations were mostly produced before the Acadian deformation, but after the Salinic disturbance. Potential source rocks of the York River Formation generated some oil during and after Acadian deformation. RI~SUMI~ Le NE de la GaspEsie est divisE en deux domaines tectono-stratigraphiques distincts: les roches cambro-ordoviciennes des zones de Humber et de Dunnage au nord et les roches siluro-dEvoniennes de la ceinture de GaspE au sud. La partie NE de la ceinture de GaspE est investiguEe pour son potentiel en hydrocarbures. Cette region est traversEe par des failles majeures d'orientation NO qui divisent la region en trois domaines tectoniques: les blocs nord, central et sud. Celles-ci ont agi en failles normales durant la sedimentation tardi-silurienne-dEvonienne prEcoce pendant la pulsation salinique et ont rejouE en failles de dEcrochement dextre durant l'orogEnie acadienne au DEvonien Moyen. Les plis rEgionaux acadiens sont de direction ENE h E. Localement, des plis d'orientation NO, associEs ~ la pulsation salinique, sont spatialement associEs g des failles de mame orientation. D'apr~s leur contenu en carbone organique total, les roches cambro-ordoviciennes ont probablement EtE de meilleures roches mires que les roches siluro-dEvoniennes de la ceinture de Gasp6 avant leur maturation. Dans les trois blocs tectoniques, des roches mbres sont observEes localement dans la Formation de York River. Celles-ci sont toutefois d'extension limitEe et marginalement matures. D'aprbs les analyses de carbone organique et de Rock-Eval, des roches mbres d'Epaisseurs plus importantes, mais de qualitE moyenne, s'observent dans les formations d'Indian Point et de Forillon du bloc central, 1~ ol) la majoritE des indices d'huile sont observds. Nos rEsultats indiquent que ces roches mires ont dEj~ gEnErE la majeure pattie de leur potentiel en hydrocarbures.
Mineralium Deposita, 2000
The Polaris deposit is one of the largest Mississippi Valley-type deposits in the world, with 22 million tonnes of ore at 14% Zn and 4% Pb contained in a single, compact orebody surrounded by dolomitized host rocks. Using detailed sampling of carbonates in the orebody and the dolostone halo, this paper aims to characterize the temporal and spatial evolution of the mineralizing system, and to understand the mechanisms that controlled the accumulation of this large, compact Zn±Pb deposit. Five types of dolomite have been distinguished, including three replacement (RD) and two pore-®lling dolomites (PD). The paragenetic order is RD1, RD2, RD3, PD1, and PD2. Pore-®lling calcite (PC) postdates all other minerals. In most cases, sul®des and dolomite did not co-precipitate, but sphalerite and galena largely overlap with RD3 and PD1. Various dolomites are dissolved or replaced by sul®de-precipitating¯uids; sul®des in turn can be overgrown by dolomites. Colloform texture in sphalerite is widespread. Fluid inclusions were studied in RD3, PD1, PD2, sphalerite, and PC. The overall ranges of homogenization temperatures (T h ) and last ice-melting temperatures (T m-ice ) for¯uid inclusions in dolomites and sphalerite are from 67 to 141°C and from )46.7 to )27.0°C, respectively, consistent with warm basinal brines with high salinities and Ca/Na ratios. Gas chromatographic analysis of these¯uid inclusions indicates low concentrations of hydrocarbons (<0.06 mol%). C, O, and Sr isotopes were analyzed for all dolomites and PC, as well as for the ®ne-grained host limestone and early diagenetic calcite (SC±RC). The isotopic values of RD2, RD3, PD1, and PD2 cluster tightly and form largely overlapping domains. With respect to the host limestone, they are depleted in 18 O, similar in d 13 C, and slightly enriched in 87 Sr. There are no regular spatial variations for¯uid inclusion and isotope data, indicating an overall geochemical homogeneity in the hydrothermal system. However, certain samples close to the fracture zones in the orebody with slightly elevated T h and 87 Sr/ 86 Sr values and depleted d 18 O values suggest that the fracture zone was the conduit for the hot brines. Based on the geological and geochemical characteristics of the deposit, we propose that sul®de precipitation at Polaris was caused by mixing of a reduced, metal-rich, sulfur-poor¯uid with a reduced, metal-poor, sulfur-rich¯uid at the site of mineralization. The metal-carrying¯uid ascended along fractures from below the deposit and was hotter than the host rocks, whereas the reduced sulfur-carrying¯uid was delivered to the site of mineralization laterally and was in thermal equilibrium with the host rocks. This model can readily explain the dissolution of dolomite during sul®de precipitation and the abundance of colloform sphalerite, as well as the low concentrations of hydrocarbons in¯uid inclusions.
Marine and Petroleum Geology, 1989
Solid bitumens occur in mineralized veins in the Lower Devonian Ochil Volcanic Formation in the Midland Valley of Scotland. Bitumens are also widespread in the Carboniferous of the Midland Valley. Gas chromatography (g.c.) -mass spectrometry (m.s.) studies undertaken on bitumens from the Devonian rocks and on Devonian and Carboniferous mudrocks show that the bitumens contain biomarkers and that Carboniferous rocks are the more likely source for the bitumens. Hydrocarbons may have migrated into the Devonian rocks along the Ochil Fault zone from a downthrown Carboniferous basin to the south of the fault. The organic geochemistry of bitumen samples from the Carboniferous rocks reflects varying degrees of biodegradation, and heating by igneous intrusions.
Organic Geochemistry, 1999
Molecular geochemical compositions of a suite of Middle Devonian sourced and reservoired oils from the Rainbow±Zama±Shekilie sub-basins in N.W. Alberta, Canada, reveal the presence of at least two oil families in the study area. The distribution of each oil family is geographically restricted to a single sub-basin, consistent with the oils being sourced locally within a series of closed generation/migration/trapping systems. The diversity in the biomarker distributions of the oils indicates the wide range of depositional environments and source materials existing in each sub-basin, rather than mixing of end member oils across dierent sub-basins. Clear maturity dierences are observed between the oils from the Rainbow and Zama subbasins. Pre-Cretaceous thermal anomalies along the reactivated regional Precambrian basement faults are proposed as one of the major causes for the relatively high maturity levels for the Middle Devonian source rocks in the study area. We infer that depositional environment and thermal maturity have had a strong impact on the geochemical characteristics of the saturated and aromatic hydrocarbons in the Rainbow±Shekilie±Zama oils, but may not in¯uence the pyrrolic nitrogen compounds to a signi®cant extent. However, recognition of possible source and maturity eects on pyrrolic nitrogen compounds in other studies suggests that these factors should be considered before the pyrrolic nitrogen compounds are used to characterize petroleum migration.
Applied Geochemistry, 2007
The KB-5 well is located at the intersection of the geothermally active Menderes and Gediz graben systems in western Turkey. Significant volumes of ''petroleum-like material'' (PLM) with its associated thermal water (120°C) erupted onto the surface during drilling from a depth of 120-132 m (i.e., from the claystone and marl-rich Early to Middle Pliocene Kolonkoya formation). The purpose of this paper is: (1) to characterize this PLM, (2) to assess the source characteristics from which the PLM was likely generated, and (3) to recognize the generation mechanism considering the geothermal-gradual versus the hydrothermal-rapid processes. Analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography-mass spectrometry (GC-MS) was carried out.
Sedimentary Geology, 2000
Petrographic, geochemical and paleomagnetic analyses of the Mississippian Turner Valley Formation provide constraints on diagenesis and fluid flow events in the Western Canada Sedimentary Basin. Paleomagnetic plugs and companion geochemical samples were taken from two drillcores, with Fullbore MicroImage log orientations. Dolomite from both wells yielded two magnetization directions. The low-temperature, low-coercivity direction is a drilling-induced remanence rather than a viscous remanent magnetization. The high-temperature, high-coercivity remanence direction is Cretaceous, and there is no sign of a primary Mississippian direction. Geochemical analyses of matrix dolomite yield d 18 O values ranging from 0.65 to Ϫ3.34‰ (VPDB standard) and d 13 C values ranging from 1.77 to 3.05‰ VPDB. The least depleted samples have stable isotope values consistent with, or only slightly depleted from, postulated Mississippian dolomite values. The remaining sample values exhibit a negative covariant trend consistent with either mixing with another diagenetic fluid or recrystallization during burial. Petrographic analysis reveals the presence of a recrystallization event that caused zoning and a gradual increase size of the dolomite crystals. This event is thought to have caused both the Cretaceous paleomagnetic remanence and the altered geochemical values. The minor enrichment in Sr radiogenic isotopes, relative to coeval seawater values, suggests that both an extrabasinal source for any fluid and large-scale fluid flow are unlikely. The results also indicate that magnetic remanences are very sensitive to visually minor changes in carbonate recrystallization from heat or pressure, so that great care must be taken in correlating paleomagnetic and geochemical data. ᭧