Research On Oil And Gas Accumulations In Northern Liaozhong Sag

A giant of oil and gas has been found in the northern part of Liaozhong sag,while the distribution of the discovered resource is very uneven.There is a large difference in the degree of oil and gas enrichment between different structures of the same structural belt.In order to discover the hydrocarbon accumulation law in the area,accumulation characteristics and enrichment rules in every zones were analyzed.Oil and gas distributing locations were found,main controlling factor of hydrocarbon accumulation was discovered,reservoiring models of oil and gas were established,and favorable target zone were pointed out.The lateral distribution of oil and gas in the northern part of Liaozhong sag is characterized by “zonation in N-S direction and segmentation in E-W direction”.The oil and gas are mainly distributed along three belts,from west to east,the western bulge,the central sag and the eastern steep slope.The longitudinal distribution of oil and gas can be divided into three layers: deep,middle and shallow corresponding to Es2-Es3,Ed2 and Ng-Nm respectively.Tectonically,oil and gas discovered mainly accumulate in strike-slip uplift zone of center sag,uplift zone,steep slope zone and gentle slope zone.From the typical oil and gas reservoirs,the discovered oil and gas reservoirs have advantage reservoiring conditions.According to the analysis of the lost wells and the failure structure,transport system is the main controlling factor for oil and gas accumulation.Based on the analysis of the factors controlling the hydrocarbon accumulation,four hydrocarbon accumulation models in the northern part of the Liaozhong sag were established: the mid-Arch uplift zone-multi-layer hydrocarbon accumulation model,the stacking fan-type conversion zone-middle layer hydrocarbon accumulation model,and the double Strike-slip conversion zone-shallow layer hydrocarbon accumulation model,steep slope zone-deep layer hydrocarbon accumulation model.Extensional faults which acted during Ng and Nm depression are effective passages for longitudinal migration of oil and gas.The increasing belt of sand-soil ratio is the dominant path for hydrocarbon migration.The effective transport path combined with the hydrocarbon expulsion map could tell favorable exploration zones: the steep slope zone of No.2 fault in Liaozhong sag and western sleep zone of northern sub-sag in Liaozhong sag.