页岩气多段压裂水平井不等长裂缝定量评价方法研究

Evaluation on the Fracture Length of Multi-stage Fractured Horizontal Shale Gas Well

页岩气井的压裂改造效果受储层地质、岩石力学性质和地应力等多重因素综合影响,微地震监测和产液剖面测试均显示单井各段改造效果差异较大。为精细评价气井产能,需快速、准确地评价单段的改造效果,本文基于注入压降试井理论对单段压后停泵压降数据进行分析,建立页岩气压裂井不稳定渗流数学模型,获取停泵后压力和压力导数的双对数曲线,从曲线形态和解释参数对单段压裂的改造效果进行定量评价。实例应用结果表明:该方法的解释结果与微地震监测以及G函数分析结果基本吻合,验证了该方法的准确性。该方法可有效实现单段缝长的定量评价,为准确开展数值模拟提供基础,同时也为井距的优化调整提供技术支撑。

Fracturing effect of shale gas well is influenced by multiple factors such as reservoir geology,rock mechani⁃cal properties and ground stress.The results of micro-seismic monitoring and liquid-producing profile test show that the effect of horizontal well reconstruction varies greatly.Therefore,it is necessary to find a fast and accurate method to evaluate the effect of single-stage reconstruction,so as to further implement gas well productivity.Based on the theory of injection pressure drop test,the pressure drop data during the process of fracturing is analyzed,and a mathematical model of unsteady seepage flow in shale gas fracturing wells is established.The double logarithmic curve of pressure and pressure derivative after the pump stop is obtained,and the reconstruction effect of single stage fracturing is quantita⁃tively evaluated from the curve shape and interpretation parameters.The application results show that the interpretation results of the method are consistent with the micro-seismic monitoring results,which verifies the accuracy of the meth⁃od.This method can quickly and accurately evaluate the effect of single-stage reconstruction and quantitatively evaluate the single-stage fracture length,providing a basis for accurate numerical simulation and a support for optimal fractur⁃ing design.