阳霞凹陷超压成因及与油气成藏关系

地层超压的形成和分布不仅与油气的运聚成藏有关，而且还直接影响油气钻井工程．因此，超压的研究和预测成为当今含油气盆地研究中的重要内容．阳霞凹陷属于库车坳陷的一个次级构造单元，钻井揭示凹陷内有超压发育．笔者应用测井资料、测试资料和地震资料分析了阳霞凹陷内超压的成因以及超压与油气成藏的关系，得出以下认识：(1)在阳霞凹陷内，上第三系吉迪克组膏泥岩中的超压是以欠压实成因为主控因素，下第三系和白垩系中的超压是以构造成因为主控因素，形成了上下两套成因机制并不完全相同的超压系统．(2)从构造演化时间上来看，巴西盖组与巴什基奇克组的超压形成时间最晚在上新世的库车组时期，早于油气大规模运移时期(库车晚期-第四纪西域期)．由于缺少断层的疏导，积聚的超压无法通过断层释放，阻挡了后期油气在巴西盖组与巴什基奇克组中聚集成藏，使得库1井所钻遇的圈闭成藏规模不足．

Origin of Overpressure and Relation with Oil & Gas Pool-Forming in Yangxia Sag

The origin and distribution of formation overpressure has an effect not only on hydrocarbon migration and accumulation, but also on drilling well technique. The study and prediction of overpressure is very important in basin study. (Yangxia) sag is a sub-tectonic unit in Kuqa depression. Drilling shows overpressure is very common in Yangxia sag. Using logs, test materials and seismic data, this paper analyzes the origin of overpressure and its influence on oil and gas pool-forming. Results show that: (1) Overpressure in Jidike Formation is mainly developed by deposition, and overpressure in Cretaceous by tectonic stress. These two overpressure systems are completely different in origin. (2) The overpressure in the Baxigai and Bashijiqike formations formed in the Pliocene when the Kuqa Formation was deposited, that is earlier than the Kuqa-Xiyu period when oil and gas migrated on a large scale. The overpressure cannot be released by the faults because there are faults around the Ku1 well area, which resisted oil and gas entering the reservoir and influenced pool-forming.