基于椭圆流模型的异常高压气藏水平井产能研究

与常规气藏相比,异常高压气藏具有原始地层压力高、驱动能量大等特征;并且在衰竭式开采过程中表现出应力敏感性。因此在水平井产能研究时,需考虑应力敏感和气体高速非达西效应的影响。针对上述情况,基于水平井渗流等势面为旋转椭球面这一特点,同时采用本体有效应力来描述岩石的应力敏感性,推导出了考虑应力敏感和高速非达西效应的异常高压气藏水平井产能公式;并通过实例分析对公式进行了验证。影响因素分析结果表明,储层物性越好或者应力敏感系数越大,异常高压气藏水平井产能受应力敏感影响的程度越大;而高速非达西效应对产能影响微弱。随着应力敏感系数的增大,产量呈线性下降趋势,随着水平井段长度的增加,产量近似呈线性增加的趋势。

Study on Horizontal Well Productivity of Abnormal High Pressure Gas Reservoir Based on Elliptical Flow Theory

Compared with conventional gas reservoirs, formations in abnormal high pressure gas reservoirs, which have higher initial pressure and ample drive energy, have stress sensitivity during the process of depletion. So the influence of stress sensitivity and high velocity non-Darcy flow effect should be considered when building the productivity equation of horizontal well. According to above case, this study based on characteristic that equipotential surfaces are rotational ellipsoid, and the primary effective stress was used to describe the stress sensitivity of rock. The equation including the influence of stress sensitivity and high velocity non-Darcy flow effect of horizontal well productivity of abnormal high pressure gas reservoir was derived. Then the formula is verified by a case study. The results of analysis of factors indicate that as the physical property of the reservoir tends to getting better, or as the stress sensibility increases, the extent of changes of horizontal well productivity will increases; and the influence of high velocity non-Darcy flow effect on horizontal well productivity was faintness. Results also show that as the increasing of stress sensitivity coefficient, the well productivity will decrease, while as the increasing of the length of horizontal section, the well productivity will increase.