焉耆盆地侏罗系油气系统特征与演化

焉耆盆地是我国西部的一个小型盆地,下侏罗统八道湾组煤系地层为主要烃源岩,中下侏罗统为主要储集层。盆地曾经历了早、中侏罗世的强烈沉降、晚侏罗世至白垩纪的强烈抬升和第三纪的再次沉降。因此,造就了侏罗纪末期和第三纪两次主要的成藏期。侏罗系油气系统经历了三个主要的演化阶段,即侏罗纪末原生油气系统形成阶段、白垩纪油气系统调整破坏阶段和第三纪油气系统调整再生阶段。侏罗纪末期是盆地主要成藏期,当时古油田的分布主要受流体势的控制,由于白垩纪的调整和破坏,到第三纪油气发生了再次充注,但油气系统的南北分异使盆地北部油气资源丰富,且以背斜油气藏为主;盆地南部则是岩性油气藏的有利分布区.

CHARACTERISTICS AND EVOLUTION OF JURASSIC PETROLEUM SYSTEM IN YANQI BASIN

Yanqi basin is a small basin in Northwest China,where the Badaowan formation of Lower Jurassic coal-bearing system is served as the main source rock and the Lower and Middle Jurassic as the main reservoir.The source rock and the reservoir had undergone the deep burial in Early and Middle Jurassic, the high uplifting in Late Jurassic and Cretaceous,and the secondary burial in Tertiary.Hence,the Jurassic petroleum system in Yanqi basin had two critical moments at the end of Jurassic and Tertiary periods which were consistent with the main generation and accumulation times of hydrocarbon.The Jurassic petroleum system in Yanqi basin had undergone three main evolution stages in geohistory.Jurassic is the formation stage of the system, during which the most paleo-oilfields were formed and their distribution was mainly controlled by the fluid potential.Cretaceous is the stage of system′s destruction,and Tertiary is the period of system′s regeneration.The Jurassic petroleum system was recharged and evolved in Tertiary from one system into two parts, with northern sag petroleum system with abundant hydrocarbon resources and southern sag petroleum system favorable for the distribution of lithologic oil and gas accumulation.