ALBERT

Description: The investigation of microbial ecosystems in permafrost sediments is an important approach to understand the role of microbial organic matter transformation in permafrost sediments for past and future climate changes, and is of high relevance in today’s geoscience research (Wagner, 2008) due to the current debate on the temperature vulnerability of permafrost deposits. Especially, the interplay between the organic substrate and the distribution of the living and past microbial communities in Late Pleistocene (Yedoma) and Holocene permafrost deposits, as well as the substrate potential of the organic matter stored in potentially thawing permafrost deposits are in the focus of the current study. Our investigation is part of the BMBF CarboPerm project an interdisciplinary Russian-German cooperation on the formation, turnover and release of carbon from Siberian permafrost landscapes. Sample material derived from terrestrial permafrost cores drilled at the coast of Bour Khaya in the North-Eastern Siberian Arctic. The gathered core material comprises Late Pleistocene to early Holocene deposits separated by an ice wedge. The microbial life markers (intact phospholipids, PLs) prove the presence of currently living microorganisms in the entire permafrost sequence and show the highest concentration in the uppermost sample indicating an abundant microbial life in the active layer. In comparison, the PL profile is strongly decreased in the underlying permafrost deposits. Nevertheless, the inventory of the Phospholipid fatty acids (PLFAs) suggests that the cell membrane temperature adaptation to cold environmental conditions is mainly regulated via the ratio between iso- and anteiso-fatty acids (FAs) as well as the ratio between saturated and unsaturated FAs. The surface samples show higher proportions of anteiso and unsaturated FAs (adaptation to cooler conditions), which might derive from the fact that surface layers are more affected from the harsh Siberian winter conditions than the deeper constantly cold permafrost deposits, where the above-ground temperature extremes are buffered due to the overlying deposits. Indeed within the deeper permafrost sequence the variations of the ratios are rather small, indicating adaptation to similar constantly cold temperature conditions. Other microbial markers (GDGTs), already partly degraded and, therefore, not indicating microbial life, reveal similarities with the TOC content and an increase especially in Late Pleistocene deposits. This suggests increased microbial life during intervals in the Late Pleistocene presumably caused by periods of moisture and temperature increased environments. Pore water analysis reveals the presence of low molecular weight organic acids (LMWOA) such as acetate, being excellent substrates for microbial metabolism. In the Late Pleistocene deposits below the ice wedge the substrate depth profiles show significant similarities to the TOC content. These points to a link between the organic matter and the LMWOA concentrations solved in the pore water and to the potential of those permafrost layers to provide substrates for microbial greenhouse gas production. In contrast, in the active layer the LMWOA concentrations are low, reflecting an active microbial turnover in the surface layers. Ester cleavage experiments on the residual organic matter resulted in the release of ester linked LMWOAs forming a potential substrate pool when released in future. These bound LMWOA profiles are even better correlated to the TOC content suggesting that the deeper permafrost deposits (older organic material)are not significantly different from those in the surface sediment (fresh organic material). Overall this indicates that the organic matter stored in the permafrost deposits and, therefore, removed from the surface carbon cycle is not much different in terms of organic matter quality than the fresh surface organic material. Considering the discussed increase of permafrost thawing, this might imply a strong impact on the generation of greenhouse gases from permafrost areas in future with its feedback on climate evolution. In a second and ongoing study, four terrestrial permafrost cores spanning from the Eemian interglacial into the Holocene form Bol’shoy Lyakhovsky Island are investigated with the focus on the differences and potential of the organic matter by comparing Eemian, Late Pleistocene and Holocene deposits. First results already reveal similar relations between the living and dead microbial communities with respect to the availability of free substrates, and the quality and amount of the total organic carbon. The results on the future potential of these deposits will also be presented.

Description: Petroleum types in the Eagle Ford resource play span the range from black oil to dry gas and are produced along regional trends that are largely maturity controlled. A total of 61 shale samples covering all maturity zones were evaluated to document organic richness, organic matter type, and maturation characteristics using established geochemical parameters. Pyrolysis experiments were then performed to simulate the generation of petroleum fluids. Termed the “PhaseSnapShot” approach, one or more target wells with known fluid properties were used as reference; a match with that composition was made using next-formed fluids generated from the shale in a closely located well of slightly lower thermal maturity than the target well(s). Phase behavior predictions from the model were calibrated using a regional pressure–volume–temperature (PVT) database compiled from the public domain. The conceptual model that best matched the PVT data were comprised of two reactive components: (1) a mixture of kerogen and bitumen that generated petroleum within the low permeability shale matrix and (2) bitumen in zones of enhanced porosity within the matrix. The combined generation of gas from both of these components as well as the strong retention of C7+ fluids in the matrix during production were required to match the calibration data. Retention of oil was needed over a broad thermal maturity range (Rock-Eval Tmax release: 440°C –475°C). A key result of this forward model is that phase behavior and bulk compositional properties of hydrocarbons can be quickly and effectively predicted using mature shale samples as long as calibration data from PVT reports are available.

Description: The Marathon 1 Mesquite well was drilled in Hamilton County, Texas, targeting the Barnett Shale with late oil window maturity. Combining a large suite of petrologic and high-resolution organic geochemical analyses on 120 core samples, we have been able to document qualitatively and quantitatively the effects of petroleum retention within and expulsion from five intervals within the Barnett Shale. Lithological heterogeneities control the composition and amount of retained fluids; the sorption of oil by solid organic matter is important in all intervals. Applying empirical formulas, we have been able to demonstrate not only that retention is primarily controlled by total organic carbon (TOC), but also that the “live” or “labile” component, rather than “dead” or “inert” carbon, constitutes the most active sorptive sites. Additional retention in the micropores provided by biogenic microcrystalline quartz (sponge spicules) accounts for the sweet spot defined by an “oil crossover” in the 9.14-m (30-ft) thick second interval. The fluorescing oil occurring in the axial chamber of the sponge spicules and that sorbed on organic particles are together enriched in saturated hydrocarbons, whereas the dispersed oil from the adjacent interval 3 is depleted in this compound class. Mass-balance calculations reveal that short-distance migration of petroleum into this “reservoir” interval (second) fractionates the generated oil into a higher quality oil by preferential retention in the order polar compounds 〉 aromatic hydrocarbons 〉 saturated hydrocarbons within the underlying organic matter and clay-rich third interval (source unit). Furthermore, molecular fractionation, i.e., a preferential expulsion of lower molecular weight hydrocarbons (n-alkanes) could be calculated. An additional practical result for source rock assessment is that corrected S2 (petroleum generated by pyrolysis) and TOC values should be calculated by combining Rock-Eval pyrolysis data on whole rocks and rocks following Soxhlet extraction. Using parameters based on unextracted rock only, the expulsion of petroleum is systematically overestimated and the degree of kerogen conversion is, therefore, concomitantly underestimated.

Description: The origin of the immense oil sand deposits in Lower Cretaceous reservoirs of the Western Canada sedimentary basin is still a matter of debate, specifically with respect to the original in-place volumes and contributing source rocks. In this study, the contributions from the main source rocks were addressed using a three-dimensional petroleum system model calibrated to well data. A sensitivity analysis of source rock definition was performed in the case of the two main contributors, which are the Lower Jurassic Gordondale Member of the Fernie Group and the Upper Devonian–Lower Mississippian Exshaw Formation. This sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals, and in the case of the Exshaw Formation, variations of thickness in areas beneath the Rocky Mountains were also considered. All of the modeled source rocks reached the early or main oil generation stages by 60 Ma, before the onset of the Laramide orogeny. Reconstructed oil accumulations were initially modest because of limited trapping efficiency. This was improved by defining lateral stratigraphic seals within the carrier system. An additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas, but not to the east of Athabasca. In the latter case, the main trapping controls are dominantly stratigraphic and structural. Our model, based on available data, identifies the Gordondale source rock as the contributor of more than 54% of the oil in the Athabasca and Peace River accumulations, followed by minor amounts from Exshaw (15%) and other Devonian to Lower Jurassic source rocks. The proposed strong contribution of petroleum from the Exshaw Formation source rock to the Athabasca oil sands is only reproduced by assuming 25 m (82 ft) of mature Exshaw in the kitchen areas, with original total organic carbon of 9% or more.

Description: A two-dimensional basin-modeling study was employed to analyze the petroleum generation and migration history of the Qingshui sag in the western depression of the Liaohe basin, northeast China. The Eocene–Oligocene ES4 and ES3 members of the Shahejie Formation (ES) are the most important source rocks responsible for the major hydrocarbon accumulations. Two sandstone beds of fan-delta origin, the Dujiatai (DJT) and the Xinglongtai (XLT), are the primary reservoir rocks in the study area. The model indicates that two migration systems can be differentiated; they are separated by the thick shale beds of the middle ES3 and ES1, which acted as important regional seals for the lower and the upper systems, respectively. The DJT bed is the most important pathway for migrating hydrocarbons in the lower system, whereas the XLT bed is a significant factor in the upper system. Calibration of the model with thermal maturity data indicates that the geological evolution is consistent with typical heat-flow values for rift basins in the range between 85 and 48 mW/m 2. All source units reached maturity during the major burial phase, which extended from the Oligocene to the Eocene. Simulation results further indicate that after a cooling period, renewed heating occurred, and additional hydrocarbons were generated during the last 5 m.y., particularly in the southern part of the basin. Sensitivity tests indicated that the faults, particularly the two main faults, served as important conduits for petroleum throughout most of the geological history. The main phase of migration occurred between the Eocene and Oligocene and was responsible for major accumulations in the west slope, the central anticline, and the central rise. Additional migration between 5 Ma and the present is significant in the southwestern area and may have brought about petroleum accumulation in the central depression and central rise. Liguo Hu received his B.S. and M.S. degrees in petroleum geology from the Southwest Petroleum Institute of China. He is currently employed as a project manager at the Liaohe Hainan Petroleum Exploration Company, PetroChina. His research interests are petroliferous basin analysis, organic geochemistry, and basin modeling.Andreas Fuhrmann joined the GeoForschungsZentrum Potsdam as a geochemist in 2002. He holds a diploma in geology from Rheinisch-Westfälische Technische Hochschule Aachen University, Germany, and, in 2003, received his Ph.D. from the Technical University of Berlin after conducting a dissertation on organic geochemistry and facies analysis in ancient and recent lake settings at the Research Center Jülich, Germany. His main research interests are the prediction of hydrocarbon composition and phase behavior, basin modeling, and the molecular geochemistry of petroleum and source rocks. Harald S. Poelchau obtained his M.S. degree in geology from the University of Colorado (1963) and his Ph.D. in earth sciences from Scripps Institution of Oceanography (1974). He worked as a research geologist for the Atlantic Richfield in Plano, Texas, and joined the Research Center Jülich, Germany, in 1988, where he was a project geologist in the basin-modeling group, and is now retired. His scientific interests include quantitative geology and computer application, sedimentology, geothermics, reservoir geology, and silicoflagellates. Brian Horsfield is a professor of organic geochemistry and hydrocarbon systems at the Technical University of Berlin, Germany, and leads the Organic Geochemistry Section at GeoForschungsZentrum Potsdam. He has 27 years experience working with and for industry in upstream research and development. His research interests include predicting fluid compositions ahead of drilling in petroleum systems and unraveling the workings of the deep biosphere. Zhanwen Zhang is the vice president of the Exploration and Development Research Institute, Liaohe Oilfield Subcompany, PetroChina. He received his M.S. degree (geology) from China University of Geosciences, Beijing, in 2001 and has great interest in basin analysis as well as natural gas geology. Tiesheng Wu is a former chief geologist of the Exploration and Development Research Institute, Liaohe Oilfield Subcompany, PetroChina. He received his B.S. degree in tectonic geology in 1965 from Beijing University. His scientific interests are tectonics and organic geochemistry, as well as modeling petroleum generation, migration, and accumulation. Yixian Chen holds a B.S. degree in geochemistry from the University of Science and Technology of China. He is a former chief geologist of the Liaohe Oilfield Subcompany, PetroChina. His research interests include organic and inorganic geochemistry and basin analysis. Jinyou Li is the director of the South China Sea Research Section in the Exploration and Development Research Institute of PetroChina's Liaohe Oilfield Subcompany. He attained his B.S. degree in geochemistry from the China University of Geosciences, Wuhan, in 1990. His scientific interests are in organic geochemistry and basin modeling.

Description: The Mackenzie Basin in northwest arctic Canada has many characteristics of a typical terrestrial, gas-rich sedimentary basin, but the origins of this important hydrocarbon province are still not well known. The three-dimensional basin modeling approach employed here illustrates not only improved capabilities but also potential pitfalls in reproducing flow in complex stratal and structural basin architectures of present-day models. Listric fault structures especially are still inadequately reproduced in most migration models. By integrating individual styles of deformation and introducing a sequence-stratigraphic approach to reproduce the stratal architecture, we are able to identify temporal and spatial relationships between sources and reservoirs. Based on these considerations, three genetic groups of oils in the basin are proposed: a first group mainly related to a Paleocene source rock, a second group related almost exclusively to an early mature source in the Eocene Taglu formation, and a third group related to the Upper Cretaceous Smoking Hills and Boundary Creek formations. In contrast to oil accumulations, gas accumulations resulted mainly from a filling event in the late Miocene, which is interpreted to be related to a decrease in pressure during a late Miocene uplift and erosional event. The Mackenzie Basin is therefore an excellent example to show that the gas proneness of a mature petroleum system, especially if the organic matter is predominantly of terrestrial origin, is mainly a function of expulsion efficiency and timing and thus is directly linked to the structural history of the basin. Karsten Kroeger joined GNS Science in 2008 as a basin modeler after his time as a postdoctoral fellow at GFZ German Research Center for Geosciences. He holds a diploma in geology from the Technical University in Karlsruhe and a Ph.D. from the Johannes Gutenberg University of Mainz on Tertiary isotope systems, paleoecology, and carbonate sedimentology. His research focuses on sedimentary systems, stratigraphy, and their application in integrated basin and earth systems modeling. Rolando di Primio joined the German Research Center for Geosciences as a senior research scientist in 2001 after having worked as an exploration geologist in the Norwegian petroleum industry for several years. He holds a diploma in geology from the Rheinisch-Westfälische Technische Hochschule Aachen, Germany, and a Ph.D. from the University of Cologne. His research interests are hydrocarbon phase behavior, basin modeling, and organic geochemistry. Brian Horsfield is a professor of organic geochemistry and hydrocarbon systems at the Technical University of Berlin, Germany, and leads the Department of Chemistry of the Earth at the German Research Center for Geosciences. He has 28 years of experience working with and for the industry in upstream research and development. His research interests include predicting fluid compositions ahead of drilling in petroleum systems and unraveling the workings of the deep biosphere.

Description: A seismic-stratigraphic investigation integrated with the structural modeling of the southern part of the Orange Basin passive margin, South Africa, demonstrates that a single tectonic event resulted in a significant alteration to both the location and style of sediment accumulation during its postrift evolution. This alteration to the margin has a significant effect on the hydrocarbon system of the area, we predict that it increased the hydrocarbon potential of the area. The evolution of the margin can be divided into two principal phases; the first comprised an overall aggradational shelf margin with little or no deformation during the Cretaceous. Deposition during the Late Cretaceous was punctuated by an episode of margin tilting that resulted in significant erosion of the inner margin and alteration of the margin architecture. The second phase of deposition, during the Tertiary, occurred to the west of the Cretaceous shelf margin and was characterized by significant margin instability and the development of a coupled growth fault and toe-thrust system. This change in passive-margin configuration and the associated switch in the location of overburden accumulation is likely to have increased the petroleum prospectivity of the deep-water part of the margin. We predict that the rapid western (seaward) migration of sediment accumulation resulted in the maturation of the high-quality distal source interval, whereas the resulting toe-thrust geometry provides suitable structural traps for the hydrocarbons. Douglas Paton currently undertakes research and teaching on integrated basin analysis at the School of Earth and Environment, University of Leeds, where his main research focus is in the structural evolution of sedimentary basins. Prior to his current position, he undertook research at Leeds in collaboration with BHP Billiton, in the Chevron Center of Research Excellence, Colorado School of Mines, and at the GeoForschungsZentrum Potsdam. He holds an M.A. degree from the University of Cambridge and a Ph.D. from the University of Edinburgh. David van der Spuy is the manager of the Resource Evaluation Department of the Petroleum Agency SA, South Africa's regulatory and promotional authority. He has 19 years of experience in the petroleum industry and has worked for Soekor and Halliburton and as a private contractor. He graduated with honors in geology from the University of Cape Town in 1984 and received his M.Sc. degree in geochemistry in 1990. His primary interests are in thermal-maturity modeling and petroleum systems. Rolando di Primio joined the GeoForschungsZentrum Potsdam as a senior research scientist in 2001 after having worked as an exploration geologist in the Norwegian petroleum industry for several years. He holds a diploma in geology from the Rheinisch-Westfaelische Technische Hochschule Aachen, Germany, and a Ph.D. from the University of Cologne. His research interests are hydrocarbon phase behavior, basin modeling, and organic geochemistry. Brian Horsfield is a professor of organic geochemistry and hydrocarbon systems at the Technical University of Berlin, Germany, and leads the Organic Geochemistry Section at GeoForschungsZentrum Potsdam. He has 27 years of experience working with and for industries in upstream research and development. His research interests include predicting fluid compositions ahead of drilling in petroleum systems and unraveling the workings of the deep biosphere.