一种页岩油藏多段压裂水平井试井分析方法

A Well Test Analysis Method for Multi-Stage Fractured Horizontal Wells in Shale Oil Reservoirs

水平井多段压裂改造技术能够极大地提高页岩油藏的采收率,因此,建立可靠的方法对准确评价多段压裂水平井压裂参数具有重要意义。针对页岩油藏多段压裂水平井,根据实际试井测试资料压力差导数曲线形态,建立了一种同时考虑主裂缝和次裂缝网的体积压裂改造试井模型,分析了模型的井底压力差和压力差导数理论特征曲线。结果表明:多段压裂水平井井底压力差及其导数特征曲线主要由6个阶段组成:井筒储集效应阶段、表皮效应阶段、主裂缝和次裂缝网双线性流阶段、次裂缝网线性流阶段、压裂改造区窜流阶段和拟稳定流阶段。参数敏感性分析发现:次裂缝网体积比越大,压力差导数曲线下凹程度越小;裂缝半长越长,压力差导数曲线上双线性流阶段持续时间越长、线性流阶段持续时间越短,曲线后期拟稳态流阶段整体下降。基于此模型提出了一种页岩油藏多段压裂水平井的压裂评价试井分析方法,实例分析表明,该模型能够有效拟合实际试井测试资料,并利用实际生产动态的产量和压力耦合分析验证了分析结果的正确性。该方法可以被推广到其他页岩油藏压裂参数评价中。

Multi-stage fracturing in horizontal well is a great way to improve the oil recovery of shale oil reservoir. Therefore, it is important to establish a reliable method for accurate fracturing parameter evaluation in multi-stage fractured horizontal wells. Based on the actual well test data and pressure derivative curves, a stimulated reservoir volume(SRV)model considering both the main and secondary fracture networks is established for multi-stage fractured horizontal wells in shale oil reservoirs, and the type curves of the bottom hole pressure difference and its derivative of the model are analyzed, which are mainly composed of six stages: wellbore storage effect stage, skin effect stage, bilinear flow stage of main and secondary fracture networks, linear flow stage in secondary fracture network, interporosity flow stage in fracturing treatment zone and pseudosteady-state flow stage. The sensitivity analysis of parameters shows that the larger the storage ratio, the smaller the sinking amplitude of the pressure difference derivative curve;the longer the fracture half-length, the longer the duration of the bilinear flow phase on the pressure derivative curve and the shorter the duration of the linear flow stage, and the pressure difference and its derivative curves of the pseudosteady-state flow stage are shifted downward. Based on this model, a well test analysis method for fracture evaluation of multi-stage fractured horizontal wells in shale reservoirs is proposed. The actual example shows that this model can effectively fit the actual well testing data. The actual production data and pressure coupling analysis verify the accuracy of the results. This method can be applied in fracturing parameter evaluation in other similar shale oil reservoirs.