--> --> Abstract: Sedimentary Model and Internal Architecture of Beach-Bar Sandbodies in Fault-Lacustrine Basins: A Case Study from the Second Member of Shahejie Formation in Banqiao Oilfield, Huanghua Depression, China, by Xiao-Fei Shang and Jia-Gen Hou; #90180 (2013)

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Sedimentary Model and Internal Architecture of Beach-Bar Sandbodies in Fault-Lacustrine Basins: A Case Study from the Second Member of Shahejie Formation in Banqiao Oilfield, Huanghua Depression, China

Xiao-Fei Shang and Jia-Gen Hou
China University of Petroleum, Beijing, China

Beach-bar is formed with waves, lake current or storm taking and reforming sandy sediments and their redeposition. It’s an important fine-grained sedimentary system in lacustrine basins. As the exploration of petroliferous basin at home and aboard entering into the middle and later stage, reservoirs of which beach-bars are the mainstay become the most important target of oil and gas exploration in recent years. Based on the integrated study of paleostructure and sedimentary environment, it shows that the beach-bar deposits of this district is come into being by the reason of the organically combination and collaboration of many controlling factors such as provenance, water energy and contemporaneous fault both on time and space. Through the study it has been found that the beach-bars in each fault block show obvious difference in terms of sediment and distribution because of the development of contemporaneous fault. Through the analysis of the data in seismic, well logs and cores, comparing the differentiation of the beach bars in each side of the fault in terms of sediment and physical property in detail, this paper build two kinds of model in which the contemporaneous fault is the main controlling factor: a model for the facies in single fault, autochthonous and continuous type of offshore beach-bar deposition, and another model for the facies in double fault, staggered and intermittent type of inshore beach-bar deposition. The special landform of contemporaneous fault in infra-littoral Banzhong fault block not only brings up adequate provenance supply but also create continuous high energy environment of water power locally. Thus the wave will discharge sand in favorable tectonic position, in the meantime, the clastic particles discharged in the fault surface will fall back because of the gravity, and so form the beach-bar deposition; on the other hand, the activity of the contemporaneous fault could add the probability of the ascent of the downthrown wall’s base level, providing the time needed for the deposition of beach-bar and avoid the stack-up of the beach-bar sand which might be caused by the frequently change of the base level to bring up the successive deposition vertically. The nearshore Bannan fault block is located between two contemporaneous faults, and because of this, this district which lies in the upthrown wall is steady in tectonic background with the development of the contemporaneous faults at each side, and is in shallow water environment in a long period; as it’s near the north Dagang source area, strong and wake intermittent waves persistently screen and elutriate the sediment from the delta, the coarse-grained conglomerate is rounding and sorting nearby, and the fine-grained sandstone is re-transporting and form the beach-bar sediment. On this basis, combining the recent sedimentation and outcrop, analysis the distribution pattern and superposition relationship of accretion and interlayer in single beach bar, and summarizing three configurations models in beach-bar, namely isolate type, vertical superposition type and lateral migration type, and reveal the mechanism of reservoir quality differentiation in beach-bars and distribution of remaining oil, thus the paper is of important guiding significance of beach-bar reservoir development.

AAPG Datapages/Search and Discovery Article #90180©AAPG/SEPM/China University of Petroleum/PetroChina-RIPED Joint Research Conference, Beijing, China, September 23-28, 2013