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Tian Yang - One of the best experts on this subject based on the ideXlab platform.
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genesis and distribution pattern of carbonate cements in lacustrine deep water Gravity Flow sandstone reservoirs in the third member of the shahejie formation in the dongying sag jiyang depression eastern china
Marine and Petroleum Geology, 2017Co-Authors: Henrik Friis, Tian Yang, Yanzhong Wang, Lingli Zhou, Shaomin Zhang, Huina ZhangAbstract:Abstract The lacustrine deep-water Gravity-Flow sandstone reservoirs in the third member of the Shahejie Formation are the main exploration target for hydrocarbons in the Dongying Sag, Eastern China. Carbonate cementation is responsible for much of the porosity and permeability reduction in the lacustrine deep-water Gravity-Flow sandstone reservoirs. The sandstones are mainly lithic arkose with an average framework composition of Q43F33L24. The carbonate cements are dominated by calcite, ferroan calcite, ankerite and a small amount of dolomite. The calcite and ferroan calcite are mainly poikilotopic blocky crystals, while the dolomite and ankerite are mainly euhedral rhombohedra crystals filling intergranular and intragranular pores. The relatively positive δ13C values (−2‰ to +3.9‰) of the carbonate cements in the sandstone reflect a mainly inorganically sourced carbon. From 32 Ma to 25 Ma, the pore water was rich in bicarbonate and Ca2+ due to carbonate dissolution in mudstone, and which were transported with the pore water from mudstone to sandstone via advection and precipitated calcite cementation in thinly bedded sandstones and some high permeability zones in the middle of medium-to-thick sandstone beds. From 12 Ma to present, abundant Ca2+, Fe3+, Fe2+, Mg2+ and bicarbonate had been transported from mudstone to sandstone via diffusion to form tight ferroan calcite cementation in the upper and lower parts of the medium-to-thick bedded sandstones. Ankerite is mainly distributed in the reservoirs associated with oil migration or charge, because change of Fe3+ to Fe2+ from oil charge may supply sufficient Fe2+ for ankerite precipitation. The center of sandstone beds (>0.6 m) is with potential of high-quality reservoirs in the research area. Carbonate cementation appears to be an important factor that controls the accumulation of oil in deep-water Gravity-Flow sandstone reservoirs in the study area.
Huina Zhang - One of the best experts on this subject based on the ideXlab platform.
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genesis and distribution pattern of carbonate cements in lacustrine deep water Gravity Flow sandstone reservoirs in the third member of the shahejie formation in the dongying sag jiyang depression eastern china
Marine and Petroleum Geology, 2017Co-Authors: Henrik Friis, Tian Yang, Yanzhong Wang, Lingli Zhou, Shaomin Zhang, Huina ZhangAbstract:Abstract The lacustrine deep-water Gravity-Flow sandstone reservoirs in the third member of the Shahejie Formation are the main exploration target for hydrocarbons in the Dongying Sag, Eastern China. Carbonate cementation is responsible for much of the porosity and permeability reduction in the lacustrine deep-water Gravity-Flow sandstone reservoirs. The sandstones are mainly lithic arkose with an average framework composition of Q43F33L24. The carbonate cements are dominated by calcite, ferroan calcite, ankerite and a small amount of dolomite. The calcite and ferroan calcite are mainly poikilotopic blocky crystals, while the dolomite and ankerite are mainly euhedral rhombohedra crystals filling intergranular and intragranular pores. The relatively positive δ13C values (−2‰ to +3.9‰) of the carbonate cements in the sandstone reflect a mainly inorganically sourced carbon. From 32 Ma to 25 Ma, the pore water was rich in bicarbonate and Ca2+ due to carbonate dissolution in mudstone, and which were transported with the pore water from mudstone to sandstone via advection and precipitated calcite cementation in thinly bedded sandstones and some high permeability zones in the middle of medium-to-thick sandstone beds. From 12 Ma to present, abundant Ca2+, Fe3+, Fe2+, Mg2+ and bicarbonate had been transported from mudstone to sandstone via diffusion to form tight ferroan calcite cementation in the upper and lower parts of the medium-to-thick bedded sandstones. Ankerite is mainly distributed in the reservoirs associated with oil migration or charge, because change of Fe3+ to Fe2+ from oil charge may supply sufficient Fe2+ for ankerite precipitation. The center of sandstone beds (>0.6 m) is with potential of high-quality reservoirs in the research area. Carbonate cementation appears to be an important factor that controls the accumulation of oil in deep-water Gravity-Flow sandstone reservoirs in the study area.
A J Van Loon - One of the best experts on this subject based on the ideXlab platform.
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lithofacies and origin of the late triassic muddy Gravity Flow deposits in the ordos basin central china
Marine and Petroleum Geology, 2017Co-Authors: Renchao Yang, A J Van LoonAbstract:Abstract Fine-grained sediments from the Late Triassic Yanchang Fm. in the Ordos Basin (central China) were studied by core analysis and geophysical logging. Part of the mudstones in this formation are stratified, part of them are unstratified; the various mudstones can be subdivided into eight types on the basis of their structures and textures. They represent a variety of environments, ranging from delta fronts and subaqueous fans to deep-water environments. Part of the sediments were reworked and became eventually deposited from subaqueous Gravity Flows, such as mud Flows, turbidity currents and hyperpycnal Flows that easily developed on the clay-rich deltaic slopes. The sediments deposited by such Gravity Flows show abundant soft-sediment deformation structures. Understanding of such structures and recognition of fine-grained sediments as Gravity-Flow deposits is significant for the exploration of potential hydrocarbon occurrences. Because fine-grained deposits become increasingly important for hydrocarbon exploration, and because the sediments in the lacustrine Yanchang Formation were deposited by exactly the same processes that play a role in the accumulation of deltaic and prodeltaic fine-grained sediments, the sedimentological analysis provided here is not only important for the understanding of deep lacustrine sediments like the Yanchang Formation, but also for a better insight into the accumulation of fine-grained prodeltaic deep-marine sediments and their potential as hydrocarbon source rocks and reservoir rocks.
J. A. Simo - One of the best experts on this subject based on the ideXlab platform.
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Depositional processes, triggering mechanisms and sediment composition of carbonate Gravity Flow deposits: Examples from the late cretaceous of the South-Central Pyrenees, Spain
Sedimentary Geology, 2002Co-Authors: Peter A. Drzewiecki, J. A. SimoAbstract:Cenomanian through Coniacian strata near the town of Sopeira in the south-central Pyrenees (northern Spain) are composed of a variety of autochthonous and allochthonous carbonate slope lithologies that are divided into six depositional sequences based on facies distribution patterns and stratal relationships. The sequences record three major phases of platform margin evolution: rifting, burial, and exhumation. During the first phase (sequences UK-1, UK-2, UK-3, UK-4, and lower UK-5), deposition occured on the edge of a wrench basin, and a normal fault located beneath the platform margin strongly influenced slope evolution. Background hemipelagic sediments on the slope were commonly redeposited by submarine slumps and slides. More intense reworking resulted in matrix-supported, slope-derived megaconglomerates (debrites). During the Cenomanian and Turonian, seismically triggered debris Flows originated at the platform margin, bypassed the upper slope, and were deposited on the lower slope as polymictic, clast-supported, matrix-rich megabreccias. The megabreccias form channelized and sheet-like bodies with erosional basal surfaces. Shallow carbonate environments backstepped during the Late Turonian and Coniacian, but displacement along the fault at this time resulted in the development of a steep submarine scarp and the exposure of Cenomanian and Lower Turonian strata to submarine erosion. Matrix-poor, margin-derived megabreccias form a thick talus pile at the base of the scarp. Some of the breccias were transported into the basin as debris falls, forming sheet-like beds. Marl eventually buried the Coniacian scarp in sequence UK-5, resulting in the second major phase of platform slope evolution. The slope profile at this time was relatively gentle, and redeposited material is less common. In the third phase (sequence UK-6), tectonically induced bankward erosion during the Santonian resulted in a high (greater than 800 m) erosional scarp with a regional east-west trend that was subsequently onlapped by siliciclastic turbidites. Rejuvenation of erosion in the same vicinity suggests that long-term tectonism controlled the position of the slope, rates of erosion, and sediment type on the slope. Sediment Gravity Flow processes are laterally and temporally related. Submarine slide and slump deposits commonly grade laterally downslope into slope-derived megaconglomerates. Debris Flows that originated at the platform margin appear to have initiated slumps, slides, and other debris Flows on the slope. Debris fall deposits are commonly capped by coarse, graded, lithoclastic packstones that may represent turbidites generated by the debris falls. Sediment fabric exerted a profound impact on depositional processes, distribution of facies, and morphology of the slope. Fine-grained, mud-rich, lower slope deposits were unstable at even moderate slope angles, and have been extensively redeposited. Redeposition of grain-rich, upper slope facies was triggered by syndepositional seismic activity and upslope migration of instability and erosion. In the presence of mud, the transport mechanisms are typically cohesive debris Flows, which were able to carry material onto the lower slope and into the basin. When no mud was available, rock falls and debris falls were the dominant sediment Gravity Flows, and their deposits are restricted to a position on the hanging wall proximal to the fault. © 2002 Elsevier Science B.V. All rights reserved.
Renchao Yang - One of the best experts on this subject based on the ideXlab platform.
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lithofacies and origin of the late triassic muddy Gravity Flow deposits in the ordos basin central china
Marine and Petroleum Geology, 2017Co-Authors: Renchao Yang, A J Van LoonAbstract:Abstract Fine-grained sediments from the Late Triassic Yanchang Fm. in the Ordos Basin (central China) were studied by core analysis and geophysical logging. Part of the mudstones in this formation are stratified, part of them are unstratified; the various mudstones can be subdivided into eight types on the basis of their structures and textures. They represent a variety of environments, ranging from delta fronts and subaqueous fans to deep-water environments. Part of the sediments were reworked and became eventually deposited from subaqueous Gravity Flows, such as mud Flows, turbidity currents and hyperpycnal Flows that easily developed on the clay-rich deltaic slopes. The sediments deposited by such Gravity Flows show abundant soft-sediment deformation structures. Understanding of such structures and recognition of fine-grained sediments as Gravity-Flow deposits is significant for the exploration of potential hydrocarbon occurrences. Because fine-grained deposits become increasingly important for hydrocarbon exploration, and because the sediments in the lacustrine Yanchang Formation were deposited by exactly the same processes that play a role in the accumulation of deltaic and prodeltaic fine-grained sediments, the sedimentological analysis provided here is not only important for the understanding of deep lacustrine sediments like the Yanchang Formation, but also for a better insight into the accumulation of fine-grained prodeltaic deep-marine sediments and their potential as hydrocarbon source rocks and reservoir rocks.
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A Late Triassic Gravity Flow depositional system in the southern Ordos Basin
Petroleum Exploration and Development, 2014Co-Authors: Renchao Yang, Zhiliang HeAbstract:Abstract Based on the analysis of numerous drill cores and drilling data, lacustrine Gravity Flow depositional systems were analyzed comprehensively in the Chang6 and Chang7 oil members (Triassic Yanchang Formation) in the southern part of the Ordos Basin. The Gravity Flow depositional systems in these members are made up of slides, slumps, sandy debris Flows, liquefied Flows, turbidity current etc, forming well developed units in the study area. Successive beds characterized by, from bottom to top, massive bedding (MB), graded bedding (GB) and horizontal bedding (HB) form well developed sequences; parallel bedding (GB) and ripple bedding (RB) are rare. It turns out that the depositional sequences are quite different from turbidites with a Bouma sequence: (1) MB represents a sandy debris Flow, (2) GB deposits in a turbidity current, (3) PB and RB are deposits that were reworked by bottom currents (traction Flow), and (4) HB represents a deep-water environment rather than Gravity Flows. Deposits in the proximal part of the subaqueous lacustrine fan consist mainly of slides, slumps and massive sandy debris Flows. Deposits at the middle part of the fan are characterized by an MB-GB-HB sequence of massive sandy debris Flows, graded turbidites and horizontally bedded lacustrine mudstones. Deposits at the end of the subaqueous lacustrine fan were mainly graded turbidites and horizontally bedded lacustrine mudstones (GB-HB sequence). Sandy Gravity Flow deposits mainly developed on the delta front and in the basin plain, extending for dozens of kilometers. They directly cover the source rock in the Chang7 oil members, which has the advantage of near-source oil accumulation. The sandstones at the bottom of each sedimentary cycle are worth further exploration because of their good reservoir properties and high oil content.
