Study On Hydrocarbon Accumulation Of Beach Bar Reservoirs In Jiyang Depression

With the continuous progress of exploration for subtle reservoirs,beach bar reservoirs have been continuously found in Jiyang Depression,which account for a big proportion in new reserves as time goes by. So it’s very important to find out the accumulation mechanism of this kind of reservoirs. In this paper,based on the oil and gas systems theory,adopted by the new theories,techniques and methods of reservoir,researched the formation mechanism and control factors of oil and gas reservoirs.Beach bar reservoirs are well developed in Jiyang Depression and distribute in different formations in different depressions. In Dongying Depression,beach bar reservoirs mainly develope in the upper submember of Es4,while they mainly develope in the Es2 in Chezheng Depression. The types of sand body of beach bar are mainly siltstones with medium porosity and low permeability.Oil-source correlation reveals that the oil of the upper Es4 in the beach bar reservoir of the Dongying Depression came from the upper part Es4 source rock. The oil of the Es2 beach bar reservoir from the Chezhen Depression originated from three different source rocks. The oil of the Dawangbei oil field and the well of D65 generated from the Es3 of the western subsag of Dawangbei sag,the oil of the well D102 came from the upper Es4 of the Dawangbei sag and the oil of the Yingxiongtan oil field originated from the mix sources of the Es1 of the Dawangbei sag and Guojuzi sag. The first oil is the normal oil and the others are the low mature heavy oil.The result applying the different hydrocarbon migration methods shows that the oil of the beach bar of the Dongying Depression is lateral migration from the hydrocarbon generation sag to the edge. The dynamic of the hydrocarbon expulsion and migration was the abnormal high pressure while the microcrack,faults and the unconformities composed the migration accumulation system. The oil of the Es1 from the Chezhen Depression migrated from well D35 to well D359 and the oil of the Es3 of the well D373 migrated from well D373 to well D371. The fault system of the Dawangbei took a significant roll during the accumulation process of the beach bar reservoir.According to the different structure location of beach bar,three patterns to form reservoir are put forward in Dongying Depression: reservior forming pattern of iner-source beach bar reservoirs,reservior forming pattern of near-source beach bar reservoirs and reservior forming pattern of out-source beach bar reservoirs. There are two patterns in Chezhen Depression: reservior forming pattern of near -source beach bar reservoirs in the center of sag and out-source beach bar reservoirs in the edge of sag.The beach bar reservoirs in Dongying Depression are characteristic of good source rocks,late accumulation period,big charging intensity,abnormal high pressure and episodic charging,while beach bar reservoirs in Chezheng Depression are characteristic of common source rocks,large difference in charging intensity,no abnormal high pressure,good porosity and permeability and controlling factor of hydrocarbon accumulation is fault.In Jiyang Depression , the source rocks supply material bases for hydrocarbon accumulation of beach bar reservoirs,the characteristics of reservoir-forming dynamic controle the accumulation models of beach bar reservoirs,the transport conditions supply migration path for hydrocarbon,the physical properties of reservoirs control the distribution scope of beach bar reservoirs.