Oil & Gas Geology ›› 2018, Vol. 39 ›› Issue (6): 1255-1269.doi: 10.11743/ogg20180615

Previous Articles     Next Articles

Origin and controlling factors of Mesozoic-Cenozoic gas condensates with high wax content and high-gravity oil in Kuqa Depression

Su Zhou1,2, Zhang Huifang2, Han Jianfa2, Liu Yongfu2, Sun Qi2, Bai Yin2, Duan Yunjiang2, Qu Yang2   

  1. 1. College of Geophysics and Petroleum Resources, Yangtze University, Hubei, Wuhan 430100, China;
    2. Tarim Oilfield Company Ltd., PetroChina, Xinjiang, Korla 841000, China
  • Received:2017-10-23 Revised:2018-08-20 Online:2018-12-28 Published:2018-10-22

Abstract: The analysis of a large number of oil samples demonstrates that the Mesozoic-Cenozoic gas condensates and high-gravity oil in Kuqa Depression feature a high wax content.The study discusses the origin and controlling factors of gas condensates with high wax content and high gravity oil in Kuqa Depression based on previous research and available data.The results show that some exinite and sapropelinite of the organic macerals in source rocks are turned into oil with high wax content,whilst vitrinite of the organic macerals produces gas condensates and high-gravity oil.These organic macerals determine the production of gas condensates with a high wax content and high-gravity oil in Kuqa Depression.The wax content in crudes is mainly controlled by three factors: oil maturity,hydrocarbon reservoir type,gas washing and oil migration.Among them,the oil maturity is predominant.The oil in Kuqa Depression is generated by thermal evolution of source rocks during its mature stage,with oil maturity Ro ranging between 0.8%-1.05%,while the crudes as a whole are characterized by a high wax content,and the wax content in crudes decreases with increasing oil maturity.Besides,the hydrocarbon reservoir type plays a secondary role.The wax content of crudes is less than 5% in dry gas reservoirs,ranges between 5%-10% in condensate gas reservoirs with low gas condensates,while is more than 10% in condensate gas reservoirs with high content of gas condensates and oil reservoirs;the wax content of crudes increases with the decrease of lo-garithm of producing gas/oil ratio of hydrocarbon reservoirs.In addition,the effect of gas washing and oil migration ranks last.Under the same oil source conditions,the higher degree of gas washing the crudes undergo,the lower the wax content of crudes will be;meanwhile the farther the crudes migrate,the lower the wax content of crudes will be.

Key words: formation mechanism, oil maturity, gas/oil ratio, gas condensate with high wax content, Kuqa Depression, Tarim Basin

CLC Number: