准噶尔盆地南缘下组合现今温压场特征及其控制因素

Present‑day temperature‑pressure field and its controlling factors of the lower composite reservoir in the southern margin of Junggar Basin

准噶尔盆地南缘下组合储层是近年来油气勘探的热点,目前南缘下组合储层多处于高温高压条件,但是温压发育特征及成因机理尚不明确。本文基于大量油田钻井实测温度和压力数据,对该区现今地温梯度及温度、压力分布特征进行了系统研究,探讨了温压场分布的控制因素。研究表明,准噶尔盆地南缘地区现今地温梯度普遍在13.2℃/km~23.7℃/km之间,平均为18.2℃/km,地温梯度高值分布于齐古断褶带中部和阜康断裂带西部。大地热流介于26.4 mW/m^(2)~46.0 mW/m2,平均值为36.1 mW/m^(2),属于准噶尔盆地内地温梯度及热流较低的地区,这主要受到盆地基底格局的控制。南缘西段卡因迪克地区压力系数以常压为主,位于四棵树凹陷的高探1井、独山1井和西湖1井下组合地层在6000 m左右开始发育强超压。南缘东段下组合层系均发育弱超压或强超压,自西向东压力系数逐渐增高。根据声波时差—有效应力关系反映南缘地区下组合地层除不均衡压实作用外,还存在横向构造挤压及有机质生烃的超压机制,喜马拉雅期较强的横向构造挤压是盆地南缘下组合发育异常高压的重要因素之一,有机质生烃是西山窑组—三工河组超压层形成的主要原因。

The lower composite reservoir in the southern margin of Junggar Basin has been a hotspot for oil and gas exploration in recent years,which is characterized by high burial temperature and pressure.However,the lack of systematic temperature and pressure research for the lower composite reservoir in southern margin of Junggar Basin has seriously restricted the petroleum exploration in the future.In this study,the present distribution characteristics of the temperature and pressure in the southern margin of Junggar Basin were studied based on massive measured temperature and pressure data of the boreholes,and then the controlling factors of temperature and pressure were also discussed.The research shows that the geothermal gradient in southern margin of Junggar Basin is generally between 13.2℃/km~23.7℃/km,and the geothermal heat flow is between 26.4 mW/m^(2)and 46.0 mW/m^(2),with an average value of 36.1 mW/m2.It belongs to the area with low geothermal gradient and low heat flow in the Junggar Basin,which is mainly controlled by the basement pattern of the basin.The formation pressure of the Caindike area is characterized by normal pressure,but the wells GT1,DS1 and XH1 in the Sikeshu Sag began to develop strong overpressure around 6000 m.According to the relationship of acoustic‑effective stress,it reflects in addition to the uneven compaction,the lower composite strata in the southern margin area also have overpressure mechanism of lateral tectonic compression and organic matter hydrocarbon generation.The Himalayan tectonic stress may be an important factor in the development of abnormally high pressure of the lower composite reservoir.Hydrocarbon generation may be the main reason for overpressure layers in the Xishanyao‑Sangonghe Formation.