复合油藏压裂水平井复杂裂缝分布压力动态特征

压裂改造是提高油田产量、改善井筒附近储层物性的重要方法，但在实际多段压裂体积改造过程中，由于地层条件复杂，导致井筒附近形成了复杂的缝网体积，因此，加强对水平井体积压裂改造试井模型的研究十分必要。基于体积压裂水平井复杂裂缝分布的渗流特征，建立径向复合多段压裂水平井试井解释数学模型，耦合储层与裂缝模型解求得Laplace空间井底压力半解析解，应用Duhamel原理得到考虑井储和表皮影响的Laplace空间井底压力解，利用Stehfest数值反演求得实空间井底压力，并绘制实空间压力动态特征曲线。根据压力导数曲线特征划分流动阶段，通过模型验证证明了该方法的正确性，进而分析了裂缝不对称、裂缝夹角、裂缝分布方式、内区半径和流度比对特征曲线的影响。结果表明，裂缝不对称交错分布有助于增大裂缝控制面积，从而减少流体流入井筒的压力消耗，早期阶段对应的压力曲线也越低；内区半径越大，压裂改造效果越明显，对应压力曲线越靠下。该模型可为多段压裂水平井所形成的复杂裂缝试井资料解释和压裂方案设计提供理论依据。

Pressure transient of fractured horizontal well with complex fracture distribution in composite reservoir

Hydraulic fracturing technology is a vital method to increase oil field production and improve reservoir properties near wellbore. In the actual process of multi-stage fracturing volume modification,complex fracture network volume formed near wellbore due to complex formation conditions. Therefore,it is necessary to strengthen the study of volume fracturing modification test model of horizontal well. Based on the seepage characteristics of complex fracture distribution for multi-stage fractured well,a well-test mathematic model of radial composite multi-stage fractured well was established. Wellbore pressure was obtained by coupling reservoir and hydraulic fracture in Laplace domain,and the impact of wellbore storage and skin factor were considered by employing Duhamel principle. Applying Stehfest numerical inversion algorithm,wellbore pressure in real time domain can be calculated and pressure response log-log curve were plotted,and flow regimes were identified by characteristics of pressure-derivative curve. The correctness of this method was proved by model verification. The effects of fracture asymmetry factor,angle between fracture and wellbore,fracture distribution,radius of inner region and mobility ratio on characteristic curves were analyzed. The results show that the fractures of asymmetric staggered distribution are helpful to increase the control area of fractures,thereby reducing the pressure drop loss of fluid flowing into the wellbore,and larger inner radius leads to smaller pressure in log-log plot. This model can provide theoretical basis for the well-test interpretation and fracturing design of complex fracture formed by multistage fractured horizontal well.