Hydrocarbon formation and accumulation of the deep Paleogene of the Jiyang Depression, Shengli Oilfield

Abstract

Using geochemistry, sedimentary and petroleum geology methods, and based on the analysis of spatial distribution of deep source rocks and sedimentary organic facies, the favorable exploration prospects in the Jiyang Depression, Shengli Oilfield are studieded. There are 4 types of sedimentary organic facies (including anoxic organic facies, anaerobic organic facies, dysaerobic organic facies and aerobic organic facies) in deep source rocks of Kongdian Formation - Sha-4 Member, Paleogene. The source rocks of Anoxic facies and anaerobic facies are discovered in the Sha-4 Member and are proved as excellent source rocks, while the Kongdian Formation source rocks compose mainly of the dysaerobic facies and aerobic facies and served as common source rocks. The whole hydrocarbon expulsion process is divided into 3 stages, including free water expulsion, hydrocarbon generation and energy accumulation, and hydrocarbon expulsion from microfractures. The hydrocarbon expulsion from deep source rocks mainly occurs in the stage of hydrocarbon expulsion from microfractures, during which there are three oil and gas migration modes with different geologic conditions, including vertical migration, lateral migration and downward migration. The studies indicated that the hydrocarbons in shallow and medium formations from the Sha-4 Member excellent source rocks of anoxic and anaerobic facies are mainly accumulated through vertical migration along the faults, while the reservoirs formed by lateral migration and downward migration are still waiting to be revealed. So there is great exporation potential for the deep Paleogene of the Jiyang Depression. Key words: Jiyang Depression, Paleogene, organic facies, hydrocarbon generation and expulsion mechanism, hydrocarbon migration, accumulation