| Biyang depression, a small Mesozoic and Cenozoic hydrocarbon rich rift basin in East China, covers a total area of 1000 km2. The deep water deposition develops well in the sag and forms extra-thick source rocks, which has great generation potential. The reservoir is abundant and various traps develop well. The predicted resource potential is 2.7×108~3.0×108t, which means that it is a real“small but rich”basin. After 30 years of exploration, we have gained great achievements. The oil-gas reservoirs discovered mainly distributes in the fan delta system (inshore sub-sea apron) in the southern steep slope region and fluvial delta system in the northern gentle slope area. Structurally, Bidian block locates in the central part of Biyang depression, in the north of Shuanghe and Zhaoao Oil-fields, in the east of Gucheng and Dupo Oil-fields and in the pitching end of Gucheng nose-like structure. The total area is about 60km2. Bi-139 well, drilled in 1986, was the discovery well and gained hydrocarbon show in 15 layers with a total thickness of 36.5m. There are 28 exploratory wells now, in which 15 wells had gained oil flow. The sandstone layer is thin and the sand distribution characteristic is not clear, which directly slows down the improvement of reserves and production. From paleogeography, it was in the lake basin center. Moreover, whether the source of major reservoir is from south steep slope region or north gentle slope is always clear. Therefore, based on the fine sedimentary micro-facies research, we applied several advanced technologies, including well logging reconstruction technology, structure-well logging restraint nonlinear reservoir prediction technology and reservoir prediction comprehensive evaluation technology, in connection with the subsurface geology condition to study the favorable sedimentary facies development mode and to predict the effective reservoir distribution, which has both practical and theoretical meaning for oil-gas exploration in this area.In view of current oil-gas exploration conditions, geologic characteristics and existed geology problems, we operate reservoir prediction and comprehensive evaluation in Member He-?by fully using the drilling data, seismic data and well logging data. The major research work includes: special seismic data processing, fine horizon demarcation and well logging reconstruction, reservoir lateral prediction, reservoir property calculation, sedimentary micro-facies analysis, reservoir evaluation and favorable target zone prediction and optimization.After careful core analysis and single well sedimentary facies analysis, we consider that the depositional facies in the research area can be divided into the middle fan and outer fan of sub-lacustrine fan and slump fan under deep water environment. The favorable reservoir is turbidite sand of different origin, and the source is from both south and north. The reservoir inversion, based on the structure-well logging restraint nonlinear inversion technology, has several advantages, including good coincidence, high apparent resolution, clear inter-well and inter-formation relationship, good fitness of the depositional environment and stable prediction. The predicted sand distribution is in NE or near SN direction; the reservoir pinching out in NW structure high direction can form up-dip pinch-out lithologic trap and structural-lithologic trap; lenticular reservoir also develops well and distributes in the hydrocarbon generation area, which is favorable for forming lithologic trap. |
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