库车前陆盆地流体压力演化对构造挤压和油气成藏的指示意义

Widespread overpressures are present in the Kuqa foreland thrust belt with the pressure coefficients up to 1.99 and intense tectonic compression has been proposed as the dominant overpressure mechanism. The reconstruction of fluid pressure evolution can indicate the timing and process of the tectonic compression if the overpressure message can be recorded by the fluid inclusions in the reservoir, which have important significance to help understanding the hydrocarbon accumulation rules and internal relationship between the tectonic compression and hydrocarbon accumulation. Therefore, the trapping pressures of fluid inclusions are modeled by the thermal dynamic equations of state based on the aqueous fluid inclusions characters and petrography observation, homogenisation temperature and salinity measurements, acquiring fluid inclusions pressure at room temperature by the Raman spectra of methane in the fluid inclusions in this study, which are used to indicate the fluid pressure evolution combined by the hydrocarbon inclusions PVT modeling. The fluid pressure evolution can indicate the timing and process of the tectonic compression in the Kuqa foreland basin and the internal relationship between the tectonic compression and hydrocarbon accumulation will be analyzed in this study. The research results can provide evidences on the study of the petroleum geology for the foreland basin in central and western Chin, coupling between basins and mountains, and uplift process of the adjacent mountain of the foreland basins.

库车前陆盆地冲断带广泛发育超压，压力系数最大为2.2，强烈的构造挤压是超压形成的主要原因。如果此超压能被储层流体包裹体所记录，恢复其古压力将可以用于指示构造挤压时间和过程，对揭示构造挤压与油气成藏过程内在联系以及成藏规律都具有重要意义。由于烃类包裹体PVT模拟只能获得油气充注时期的捕获压力，而且克拉苏冲断带油包裹体不发育。因此，本研究将系统开展盐水包裹体特征和岩相学观察、均一温度和盐度测定、利用激光拉曼光谱仪测定盐水包裹体中甲烷拉曼峰来获取常温下包裹体内部压力，再通过流体热动力学方程模拟流体包裹体捕获压力，同时开展烃类包裹体PVT模拟综合反应储层压力演化过程，用于指示库车前陆盆地遭受的构造挤压时间和过程，综合分析构造挤压与油气成藏过程的内在联系。此研究可以为中国中西部前陆盆地油气地质及盆山耦合和邻近山脉隆升过程相关基础性研究提供依据。

本研究在系统开展盐水包裹体特征和岩相学观察、均一温度和盐度测定、利用激光拉曼光谱仪测定盐水包裹体中甲烷拉曼峰基础之上，通过流体热动力学方程模拟流体包裹体捕获压力，揭示储层压力演化过程，用于指示库车前陆盆地遭受的构造挤压时间和过程，综合分析构造挤压与油气成藏过程的内在联系。研究结果表明库车前陆盆地在距今5Ma以来到现今遭受了持续的强烈构造挤压作用，构造挤压对油气成藏过程具有重要的控制作用。