准噶尔盆地腹部阜康深凹带侏罗系成藏规律

Jurassic reservoir development in Fukang Deep Sag,Central Junggar Basin

准噶尔盆地腹部阜康深凹带地层埋藏较深,断层不易识别,圈闭隐蔽,与凸起带以大型构造圈闭为主的油气藏在成藏规律上存在显著差异。在对阜康深凹带油气来源、运移通道、运移动力及成藏时间等成藏过程研究的基础上,分析油气运聚过程和成藏主控因素。首先应用地质与地球化学的分析方法,发现阜康深凹带的油气主要来自于八道湾组淡水环境下形成的煤系烃源岩;然后结合异常压力、运移输导特征及油气成藏期次的分析,认为油气从八道湾组排出之后,在八道湾组和三工河组砂体中发生过长距离侧向运移,之后通过走滑断层,垂向运移至上部的头屯河组圈闭中聚集成藏。通过对阜康深凹带成藏主控因素的分析,认为头屯河组油气藏的形成主要受超压、断裂、圈闭及三者良好匹配的控制,并在此基础上,建立了该区的油气成藏模式。

Jurassic reservoirs were deeply buried in the Fukang Deep Sag,where faults are difficult to identify, and traps are subtle,leading to significant differences in reservoir-forming controls where they are dominated by large structural traps in the uplift zone. The process of oil and gas migration and accumulation and the main factors controlling hydrocarbon accumulation were analyzed based on the study of oil and gas source,migration pathway, migration agent and timing of reservoir development. Geological and geochemical analyses showed that oil and gas in the Fukang Deep Sag mainly came from coal-measure source rocks which were deposited in a freshwater environ-ment in the Badaowan Formation. Comined with the analyses of abnormal pressure,oil and gas migration charac-teristics and reservoir-forming stages,it was deduced that,after discharge from the Badaowan Formation,oil and gas laterally migrated for a long distance in sand bodies of the Badaowan and Sangonghe formations, and then, through strike slip faults,vertically to traps in the Toutunhe Formation. The analyses of the main factors controlling hydrocarbon accumulation in the Fukang Deep Sag indicated that the formation of oil and gas reservoirs in the Tou- tunhe Formation was controlled by overpressure, fault,trap and the good matching of them. A reservoir develop-ment model of the study area was established.