243 / 2019-06-29 21:37:36

Deep-water channels and its architecture in lacustrine: a case study on subsurface oil reservoirs in the western Liaohe Basin, China

deep-water channel, architecture, gravity flow deposits, debris flow deposits, turbidity flow deposits, Liaohe Basin, Shahejie Formation

With deep-water gravity flow deposits becoming the most active area for oil and gas exploration in continental lacustrine, deep-water channel research in continental lacustrine has attracted extensive attention. At present, the research on deepwater channel mainly focuses on sedimentary characteristics, distribution, formation mechanism and geophysical response. Despite their significance and widespread occurrence, deep-water channels remain a key research challenge in sedimentological community, because of their three- dimensional complexity and diversity. Liaohe Basin is located in the northeast of China. It is a rifted basin with Mesozoic and Cenozoic strata. During the third member of the Paleogene Shahejie formation，It's a deep lake here, and there are many deep-water channels deposits. Based on core data of 5 coring wells and logging data of 374 wells, the sedimentary characteristics and architecture of deep water channels in the third member of Paleogene Shahejie Formation in Western Liaohe Basin are studied. The results show that gravel debris flow, sandy debris flow and turbidity flow can be recognized in the third member of Shahejie Formation. The composition of gravel in gravel debris flow is complex and varied in size, and a large number of floating gravel can be seen. It is massive or concrete structure. There are a large number of argillaceous sandstone strips, argillaceous tear debris, carbonized plant debris and various sedimentary structures in the sandy debris flow. AA and ABC parts of Bauma sequence are common. Lithofacies types include matrix-supported conglomerate, granular-supported conglomerate, granular-supported conglomerate and sandstone, granular-supported sandstone, siltstone and mudstone. There are many types of lithofacies assemblages in the vertical direction. The fault bench is formed by three NE-trending geese-like normal faults（named F1, F2, F3）. Conversion of gravity flow type is controlled by fault bench. Scale of F1 is the largest, and its fault throw is about 250 meters. The distribution of gravel debris flow is located in the footwall of F1. The distribution of sandy debris flow is located in the hanging wall of F1. It has been shown that it has a large slope between the footwall and the hanging wall of F1, which deepens the lake. Under these conditions, Fluid transformations occur. Gravel debris flow is converted to sandy debris flow. Sandy debris flow is converted to turbidity flow in the hanging wall of F3. Macroscopically, the sedimentary bodies formed by deep-water channels are zonal or tongue-shaped, extending further to the center of the lake. The superimposed pattern of the sedimentary bodies formed by deep-water channels is complex, which is the direct cause of the complex reservoir distribution. It is significance to reveal the heterogeneity of deep-water oil and gas reservoirs, and it can only be found in the study of subsurface oil and gas reservoirs with single deep-water channel as the research object.