准噶尔盆地莫索湾凸起侏罗系超压成因

Genesis of Jurassic overpressure in the Mosuowan uplift of the Junggar Basin

超压成因分析是压力预测和油气成藏研究的基础,准噶尔盆地腹部莫索湾凸起侏罗系超压分布普遍,且与油气成藏关系密切复杂,亟待深入开展超压成因研究。综合运用测井曲线组合分析法、Bowers法、声波速度—密度交会图法、孔隙度对比法和综合分析法等探讨了超压的成因。研究表明,准噶尔盆地莫索湾凸起侏罗系普遍发育超压,主要位于4000~4500 m以深地层,压力系数为0.92~2.11,平面上东部超压较强,压力系数可达2.11,西部较弱,压力系数可达1.6。声波时差、密度及电阻率测井曲线对超压的响应较为明显,表现为均存在不同程度的反转。多方法综合判识准噶尔盆地莫索湾凸起侏罗系地层超压以传导型成因超压与化学压实复合成因超压为主,且东部化学压实贡献略高于西部,欠压实成因贡献弱或者无。

The study of the causes of overpressure is the basis for stress prediction and the research on hydrocarbon accumulation.The Jurassic overpressure is widely distributed in the Mosuowan uplift,located in the central part of the Junggar Basin,which is closely related to hydrocarbon accumulation,making it an important topic for further research.This study comprehensively utilizes various methods such as log curves combination analysis,Bowers method,velocity-density crossplotting,correlation of porosities,and comprehensive analyses to discuss the causes of overpressure.The research shows that overpressure is generally developed in the Jurassic of Mosuowan uplift,Junggar Basin.The overpressure is mainly located in the deep formation of 4000-4500 m,and the pressure coefficient ranges from 0.92 to 2.11,with an average pressure coefficient of 1.33.On the planar scale,the eastern part experiences more significant overpressure,with pressure coefficients of up to 2.1,while the western part has relatively weaker overpressure,with pressure coefficients reaching up to 1.6.Sonic transit time,density,and resistivity log responses show clear indications of overpressure,with varying degrees of reversal.Based on the comprehensive analysis using multiple methods,it is determined that the overpressure in the Jurassic formations of the Mosuowan uplift in the Junggar Basin is mainly influenced by hydrocarbon generation and pressure transmission.The contribution of chemical compaction is slightly higher in the eastern part than in the western part,while the contribution of under compaction is weak or nonexistent.