双重介质低渗透油藏水平井试井模型

Horizontal Well Test Model of Dual-Medium Low-Permeability Reservoir

针对低渗透油藏中非线性渗流对试井压力动态特征产生较大影响的问题,建立了考虑非线性系数的双重介质低渗透油藏水平井试井新模型,用有限元方法(FEM)进行求解,绘制试井典型曲线,对数值解的正确性进行验证,并对非线性系数、渗透率模数、窜流系数、顶底边界等相关参数进行影响分析。结果表明,从基质到裂缝的非线性流动主要影响压力导数曲线“凹子”的深度和位置,当非线性系数增大时,“凹子”变浅,并向右移动。在考虑应力敏感性时,压力及导数曲线上移,压力导数曲线偏离达西模型下的中期和晚期径向流的水平段,压力导数曲线值大于0.5,随着渗透率模数的增加,曲线后期上翘更加严重,“凹子”的深度和位置不变。采用该模型对实际区块的压力测试数据进行拟合分析,得到良好的拟合效果。研究结果为水平井开发低渗透油藏提供了一定的理论支持。

A new horizontal well test model of dual-medium low-permeability reservoir was established to improve the well test pressure performances result from the nonlinear flow in low-permeability reservoir. FEM( Finite element method) was adopted to solve this new well test model. The typical well test curves were drawn to verify the validity of numerical solution and analyze the effects of nonlinear flow,permeability modulus,cross-flow coefficient,top and bottom boundaries and other related parameters. Result indicates that the concave depth and position of the pressure derivative curve are mainly dependent on the nonlinear flow from the matrix to the fracture system.The concave part becomes shallower and moves to the right as the nonlinear flow coefficient increases. The pressure and its derivative curves move up when the stress sensitivity is taken into consideration. The pressure derivative curve deviates from the 0.5 case in the middle-late radial flow under Darcy Flow Model. There is a significant upturn in the late stage with the increase of permeability modulus and without the change of the concave depth and position. A favorable agreement between the fitting and field test data was gained by using this new well test model.This research could provide certain theoretical reference for the low-permeability reservoir development with horizontal well.