CHARACTERISTICS AND HISTORY OF HYDROCARBON GENERATION AND EXPULSION OF SOURCE ROCKS IN THE FIFTH MEMBER OF XUJIAHE FORMATION IN WEST SICHUAN DEPRESSION,CHINA

摘要

The Upper Triassic Xujiahe Formation is the main source rock system in the West Sichuan Depression of the Sichuan Basin,China,while the source rock of the fifth member (or Xu 5 Member) of the Xujiahe Formation is a new area of in-source oil and gas exploration and development in the West Sichuan Depression.In this paper,geological,logging,drilling,and experimental test data were used to analyze the development characteristics of source rocks and the characteristics of organic matter abundance,type and maturity in the Xu 5 Member.In addition,basin simulation technology was used to quantitatively restore the hydrocarbon generation and expulsion history of the Xu 5 Member of the Xujiahe Formation.The results show that the source rocks of the Xu 5 Member have high abundance of organic matter.The main type of organic matter is type III,followed by type II.Therefore,the source rock has the co-production capacity of oil and gas in a mature-high-mature stage.The research also found that the source rocks of the Xu 5 Member have been in a continuous hydrocarbon generation and expulsion process after the Late Triassic.However,there are obvious differences in hydrocarbon generation intensity in different structural units.The Xiaoquan Fenggu Structural Belt has the highest hydrocarbon generation and expulsion intensity.In short,the in-source oil and gas system with the Xu 5 Member as the source of oil and gas charging is the main prospecting target of this area in the future.