库车坳陷东部地层压力特征与油气成藏

Characteristics of Formation Pressure and Its Relationship with Hydrocarbon Accumulation in the Eastern Part of Kuqa Depression

库车坳陷东部气藏既有常压气藏，也有超压气藏，对气藏实测压力特征进行了系统分析，探讨了地层压力与油气成藏之间的关系。结果表明，库车坳陷东部地层压力在结构上划分为膏盐岩封闭层压力结构和泥岩封闭层压力结构，压力分布在22．8～107．5MPa之间，压力系数分布在1．16～2．29之间，常压和超压并存，且以超压占优势。纵向上，浅部一般为常压，深部一般为超压；平面上，压力和压力系数均由南向北表现出逐渐降低的趋势。在源一储压差作用下，深部超压流体对浅部的储层发生强充注。气藏压力反映出各气藏保存条件存在差异，迪那地区地层保存条件最好，依南2井次之，依深4井最差。根据地层压力和油气藏剖面特征，库车坳陷东部存在远源封闭型强超压成藏、近源半封闭型超压成藏和远源封闭型常压成藏3种油气成藏模式。

Several reservoirs with normal pressure and overpressure have been discovered in the eastern part of Kuqa Depression. The testing pressure data were collected and the relationship of formation pressure and hydrocarbon accumulation was discussed. The results showed that pressure framework was classified as salt seal layer and mudstone seal layer pressure structure, and that the values of pressure and pressure coefficient are 22.8 to 107.5 MPa and 1.16 to 2.29, respectively. Vertically, normal pressure is distribu- ted in shallow layers and overpressure in deep layer. Pressure and pressure coefficient both display a fea- ture of decreasing trend from north to south direction. Deep overpressure fluid is strongly charged into shallow layer by the source-reservoir pressure difference. Preservation difference of gas reservoir reflected by reservoir pressure and pressure coefficient, indicate Dina wellblock is best, Yinan2 wellblock is the next and Yishen4 wellblock is bad. According to the characteristics of formation pressure and oil and gas reser- voir profiles, three hydrocarbon accumulation models are summarized as the distal enclosed accumulation model with strong overpressure, the proximal sub-enclosed accumulation model with overpressure and the distal enclosed accumulation model with normal pressure.