Comparison Of Characteristics Of Source Rocks Of Salt Zone And Saltless Zone,Dongpu Depression

Dongpu depression is one of the typical salt lake facies depression in China,the oil and gas resources are rich,the exploration degree of shallow is relatively high,the third layer of Shahejie formation is the most important target layer of oil and gas exploration in the future.The previous exploration practice shows that the salt bearing strata have important control effect on the distribution and characteristics of source rock.Based on the data of drilling,logging and geochemical logging,this paper analyzes the quality of hydrocarbon source rock in the salt zone,transition zone and salt free zone in the third member of Shahejie formation in Dongpu depression.The organic matter content of source rock in the salt zone is high?TOC is about 0.743%¹.250%?and the type is good?type?and type?₁?.The quality of hydrocarbon source rock in salt free zone is poor?TOC average is between 0.305%⁰.375%and organic substance type?₂ and?type?.The quality of the source rock in the transitional area is between the two.By analyzing the differences of ancient,paleoclimate,ancient productivity,source types and preservation conditions of typical wells in salt zone,transition zone,salt free zone,the formation model of different environmental hydrocarbon source rocks was established.When the source rocks of the third layer of Shahejie formation in salt zone are formed,it is the salt water environment with higher salinity and the climate is more suitable.The source of organic matter mainly comes from Aquatic organisms such as algae,with high paleo productivity?mean 657.3 g/?m²·a??and reductive conditions conducive to organic matter preservation.However,when the salinity is too high?2.0%?,the climate becomes dry,the source of organic matter is insufficient,and the abundance of organic matter decreases.The hydrocarbon source rocks in the transitional zone are brackish water environment,organic matter source type is aquatic and terrestrial mixed type,lower Paleozoic productivity compared with saline zone?390.6g/?m²·a??,hydrocarbon source rock quality is poor.The ancient productivity of source rocks,in close to the salt rock development area,is higher.And its organic matter source type and preservation condition is good,with the formation of good source rock conditions.When hydrocarbon source rocks in salt free zone are formed in fresh water environment,the source of organic matter is mainly aquatic organisms,the whole ancient productive force is low?370.7 g/?m²·a??,and the storage conditions of organic matter are relatively poor.However,in the period of humid climate,it has high paleo productivity.So the saltless area zone hydrocarbon source rock is poor,but there is a layer of high abundance of organic matter,which is of guiding significance for the exploration of large low abundance of organic matter exploration area in southern Dongpu depression.