Research On Oil And Gas Accumulation Mechanism And Models Of S Oil Layer In West Slope Region

By using petroleum geological, geochemistrial, and geophysical data and combining geological research with experimental analysis, this paper studies oil and gas S oil layer accumulation in west slope region, north of Songliao basin. On the premise of overall analysis of geologic structure and depositional setting, on the basis of study on oil accumulation condition (such as condition of hydrocarbon source rocks, reservoirs, cap rocks, and traps), it can be concluded that there are mainly 5 types of oil-gas pools reservoirs of anticline, lithological up-dip, structure-lithology, lenticular body,fault seal of S oil layer in west slope region, and that gas stays upper while oil lower in the same oil layer and oil-gas mainly lies in Taikang uplift zone and its nearby, and that oil-gas reservoirs belongs to anticline and structure-lithology in Taikang uplift zone and lithological up-dip in western overlap zone. According to the analysis of these 5 typical oil-gas reservoirs, S0+1 oil layer has 3 types of oil-gas reservoirs which are structure-lithology, fault-lithology and lithology. Structure-lithology oil-gas reservoirs are mostly located in the middle of Taikang uplift zone, fault-lithology in Tailai area, and lithology in Fulaerji area. S2+3 oil layer has structure, structure-lithology oil-gas reservoirs which lie in the mid-south of Taikang uplift zone and lithological up-dip located in Fulaerji area. Based on oil-gas distribution law, by means of correlation oil and sourcerock oil gonane isomeric parameter and relative content of pristane and tane, it draws to a conclusion that in west slope region oil of S oil layer mainly comes from K1qn sourcerock in Qijia-Gulong sag. Study on the components and isotope of in west slope region gas shows that gas from in Fulaerji oilfield of west slope is typical biogas and that gas of other areas is mixed by oil-type gas coming from Qijia-Gulong and local biogas,which mainly migrates through sand body and fault. Oil and gas which migrated from source area (Qijia-Gulong sag) to west slope region can be basically divided into 3 main pathways. Oil and gas migrates mainly through middle pathway, in way of convergence with large volume and concentrated direction, accumulating in the middle of Taikang uplift zone and east of western overlap zone. On the basis of autogeny illite K-Ar isotope dating of 5 oil-sand specimens in S oil layer and matching with expulsion hudrocarbon of hydrocarbon source rock, it can be concluded that oil-gas injection of S oil layer has 2 stages, one of which is the end of K1n sedimentation, the other is form the end of K2m sedimentation to the early of Eogene period. According to these mentioned above, it can be concluded that there are 4 types of accumulation model in west slope region, that is, sandstone up-dip trap, structure and structure—lithology trap, fault—lithology trap, sandstone lenticular body trap, and that oil-gas accumulation and distribution are mainly controlled by some factors that is trap growth, relationship of between trap and space orientation of oil-gas migration pathway, connection area of centripetal flow and centrifugal flow, oil-gas preservation condition and unconformability. At last, favorable prediction for test areas shows that it is sandstone up-dip trap of Du405 and Lai63～Lai27 well that should be expecting target areas of next oil and exploration.