The Contribution Of High Quality Source Rocks To Oil And Gas Accumulation In Yanchang Formation In Ordos Basin

The Yanchang formation in Ordos Basin is the first set of sedimentary rock series after the formation of inland Lake Basin.The source rocks of Chang 7 and Chang 9 are well developed and of good quality,that is,as the Yanchang formation of high-quality source rocks.In this paper,the source rocks of Yanchang formation in Xiasiwan area of Ordos Basin are studied by using Organic geochemistry analysis technique,logging interpretation data and regional evolution history.According to the abundance,type and maturity of organic matter of source rocks,the hydrocarbon-generating potential of each layer of source rocks are evaluated.The main hydrocarbon-generating potential of Chang 7 TOC is 1.87~5.21%,and the oil-producing potential is 7.57~19.12mg/g,the type of organic matter is II 2,the thermal evolution degree is high;Chang 9 Toc is mainly 4.55~6.73%,oil production potential 7.12~15.62 ma/g,the type of organic matter is II 2-II 1,the thermal evolution degree is high,so Chang 7 and Chang 9 are divided into high quality source rocks,by using ?lgR and logging data,the distribution characteristics of mudstone thickness and organic carbon content in plane and space of different high quality source rocks in the study area are described.According to organic geochemical analysis data of Hydrocarbon Source Rock samples from Chang 7 and Chang 9 and crude oils samples from Chang 4+5,Chang 6 and Chang 8,the correlation between crude oil of different oil family and source rocks is researched,the genetic types of crude oil and the contribution difference of different source rocks are determined.Chang4+5 and chang6 crude oil samples show a good relationship with chang7 dark mudstone on the variation of multiple biostandard parameters,indicating that the main source rocks of the two sets of oil formations come from chang7.In addition to the self-generated and self-stored oil and gas resources in chang8 reservoir,chang8 reservoir mainly comes from chang7,and chang9 high-quality source rock also makes a small contribution to each reservoir group.In this paper,the difference of hydrocarbon generation between black shale and dark mudstone is determined by using thermal simulation experiment data of hydrocarbon generation of different lithology source rocks,and the quantitative hydrocarbon generation model of source rocks is established,and the hydrocarbon generation intensity and resource quantity of different source rocks are calculated,the contribution of high quality source rocks to hydrocarbon accumulation is discussed.The oil and gas resources of Yanchang formation in Xiasiwan exploration area are mainly derived from the high quality source beds Chang 7 and Chang 9,and the contribution of Chang 7 is greater,chang 6 formation also contributed a little as a better source bed in the study area.