Characteristics and enrichment conditions for Cenozoic lithological reservoirs in the Jiyang Depression
Li Yunzhen1, Liu Zhen1, Zhang Shanwen2, Hao Qi1, Lü Xixue2
1. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum, Beijing 102249;
2. Shengli Oilfield Branch Company, China Petroleum & Chemical Corp., Dongying, Shandong 257000
The Jiyang Depression is a Cenozoic rifted basin full of oil and gas.In different zones, there are apparent differences on the degree of hydrocarbon enrichment.There might be three conditions of enrichment for lithological reservoirs in the depression.1)Rich oil resources were substantial conditions of hydrocarbon enrichment,because there were many sets of source rocks with huge thickness, widespread distribution, large resource extent and favorable contact relation between sandbodies.2)High quality sandbody lithological traps were accumulating conditions of hydrocarbon enrichment.These traps should have characteristics of large-scale,favorable types of reservoir facies and favorable reservoirs.Large-sized sandbody lithological trap or many overlaying small-sized lithological traps were forms of expression for large-scale traps.Favorable reservoir facies involved fan delta,sublacustrine fan and river facies.In these fades, the middle of fan was the best place for hydrocarbon enrichment.Favorable reservoirs characterized with good types of sandbody and matching induced porosity.3)Confluence pathway was carrier condition of hydrocarbon enrichment.Abundant hydrocarbon enriched in high quality sandbody traps by fault confluence pathway and porous(or crack)confluence pathway which were important factors for hydrocarbon enrichment.So the conditions of enrichment in the Jiyang Depression displayed the characteristics of major factors.Three basic conditions controlled the formation of enrichment.To the distribution of hydrocarbon in space,only few districts could form the enrichment.