超深致密裂缝性砂岩气藏储层裂缝预测研究——以库车坳陷克深8气藏为例

Prediction of Fractures in Extra-deep,tight, and Fractured Sandstone Gas Reservoirs: An Example from Keshen 8 Gas Reservoir, Kuche Depression

在超深致密裂缝性砂岩气藏储层的研究中,裂缝既是主要的油气运移通道也是重要的储集空间,是整个气藏高产的地质基础。库车坳陷克深8气藏是典型的超深致密裂缝性砂岩气藏,裂缝的发育具有很强的不确定性和非均质性。研究裂缝的发育规律,进行裂缝数值模拟,预测其空间展布,可以有效地指导整个气藏的勘探开发、有利区优选、储层改造。由于研究区储层埋深超过5 500 m,地震资料精度有限;针对超深致密裂缝性砂岩气藏采用ANSYS有限元分析法,根据古地应力场产生裂缝、现今地应力场改造裂缝的思路,通过模拟古、今地应力场的分布状态,依据岩石破裂准则及能量守恒原理,在露头、钻井、测井、动态多因素约束下通过对裂缝参数进行关键点赋值,采用ANSYS有限元分析法进行裂缝数值模拟,建立了与实测数据高度匹配的裂缝模型。

After our study on extra-deep, tight, and fractured sandstone reservoirs, it is found that, as not only the main migration pathway but also the important reservoir space, fractures are geological foundation to realize a high-yield for whole gas reservoirs. In Kuchen Depression, Keshen 8 gas reservoir is just a typical extradeep, tight, and fractured sandstone gas reservoir; furthermore, its fracture development is strongly uncertainty and heterogeneity. So,for these fractures, to understand their development laws, to carry out numerical simulation, and to predict their space distribution may effectively guide an overall exploration and production. In this study area, the burial depth of reservoir is always over 5500 m,bringing about weak precise in seismic data. In addition, a method called ANSYS limited element analysis was adopted for these gas reservoirs. This method firstly simulates the distribution of paleo and current stress fields, secondly implements an assignment of critical fracture parameters under constraints of multiple factors including outcrop observation, drilling, well logging, and dynamic performance, thirdly carries out a numerical simulation of fractures,finally establishes a fracture model matching highly with actually tested data. It's an effective method to study fractures in reservoirs.