Prediction and Early-stage Evaluation of Paleogene Hydrocarbon Source Rocks in the Xisha Trough Basin
西沙海槽盆地古近系烃源岩预测与早期评价

The Xisha trough basin is a favorable oil and gas exploration area on the northern continental slope of the South China Sea.The Paleogene strata in this basin are characterized by the development of Eocene and Oilgocene sediments.Eocene strata mainly developed a river-lacustrine facies hudrocarbon depositional system, and the kerogen source rock might be mainly of ⅠandⅡtype,with high TOC content.This horizon is very thick in the central sag,and hence it is the potential high-quality hydrocarbon source rock.Oilgocene strata are characterized by offshore and shelf sea sediments,and the kerogen source rock is probably mainly ofⅢtype,and hence this horizon is also the mainly hydrocarbon source rocks.The result of maturiry and evolution simulation of source rock indicates that the Eocene lake source rock and the lower Oilgocene marine source rock already reached the mature or over-mature phase,whereas the upper Oilgocene source rock arrived at the mature phase only in part of central sag.Miocene rock was not mature because of very shallow burial.