运用弹性位移理论预测盐下超深储层裂缝有效性——以克深2,8号构造为例

Application of elastic displacement theory for effective fracture prediction in ultra-deep reservoir:Taking Keshen 2 and 8 Blocks as examples

塔里木盆地库车坳陷克深2,8号构造盐下深层的白垩系巴什基奇克组主要为裂缝性低孔砂岩储层,岩心实验及单井测试资料表明,裂缝是影响单井产量的主要因素。研究发现,克深2号气藏部分井存在裂缝少但产量高、裂缝多但产量不高的现象,说明裂缝的多少并不是决定产量的关键性因素。为此,文中尝试采用基于岩石力学的弹性位移理论,从裂缝有效性的角度对克深2,8号构造进行二维数值模拟。通过模拟,可计算最大哥伦布剪切应力分布状态。最大哥伦布剪切应力越高,岩石越易破裂,裂缝有效性就越高。模拟结果表明:克深2号构造裂缝有利发育区位于构造的西部、中部地区,构造东部裂缝的有效性较低;克深8号构造的裂缝有效性,模拟结果整体上高于克深2号构造,且呈带状分布。这一结果与岩心、钻井漏失及测试资料吻合程度高。

The subsalt Bashijiqike Formation of Keshen 2, 8 Blocks in Kuqa Depression, Tarim Basin is fractured low-porosity sandstone reservoir, core experiments and single well test data show that the fractures are the main factor that influences the production of single well. In Keshen 2 Block, some wells with less fractures have large output, but some wells with more fractures have little output, this shows the fracture numbers is not a key factor to production. Therefore, this paper tries to use elastic displacement theory to simulate Keshen 2, 8 Blocks two-dimensionally for fracture effectiveness. Simulation can calculate the maximum Columbus shear stress distribution, the bigger the maximum Columbus shear stress is, the easier the rock is more easily broken, the more effective the crack is. The results show that the favorable fracture development zone of Keshen 2 Block is located in the western and central parts of the structure, in the east, the fracture effectiveness is lower; simulation result of Keshen 8 Block is higher than that of Keshen 2 Block. The results of numerical simulation match the core, drilling loss and test data.