微注入压降测试在页岩气储层评价中的应用

页岩气储层渗透率非常低,采用常规压力恢复测试方法需要很长时间才能达到径向流阶段,而微注入压降测试方法可以在较短时间内达到拟径向流阶段,可以快速有效评价储层参数。基于微注入压降测试基本原理和测试流程,将微注入压降测试分为两个阶段开展分析:裂缝闭合前分析和裂缝闭合后分析。结合PY-1井微注入压降测试数据开展实例分析,裂缝闭合前分析评价了页岩储层滤失类型;裂缝闭合后阶段评价了原始储层压力及渗透率等物性参数。微注入压降测试解释储层原始压力与现场静压测试结果一致,结果表明解释结果可靠,为快速评价页岩气储层参数提供指导。

Application of Pre-frac Injection Falloff Diagnostic Test in the Evaluation of Shale Gas Reservoir

The permeability of shale gas reservoir is extremely low. Conventional build-up test used for reservoir evaluation have low efficiencies due to the long time for detection of radial flow. However, the pre-frac injection falloff diagnostic test method can achieve the radial flow in a short time, effectively evaluate the reservoir physical parameters. Based on the basic principle of pre-frac injection falloff diagnostic test, the analysis of pre-frac injection falloff diagnostic test is performed in two parts: pre-closure analysis (PCA) and after-closure analysis (ACA). The test data of PY-1 well was analyzed. Fluid leak-off type of reservoir was evaluated by PCA. Initial formation pressure and effective permeability were obtained by ACA, consistent with the static pressure test result, which indicates that the evaluation results are reliable and provide guidance for the rapid evaluation of shale gas reservoir parameters.