三重介质油藏渗流模型与试井样版曲线

针对三重介质碳酸盐岩储集层在钻完井和开采过程中井周围产生污染带以及储集层本身的非均质情况, 建立了考虑井筒储集效应和表皮效应的三重介质复合油藏有效井径试井解释模型。通过Laplace 变换法对模型进行了求解, 得到了Laplace 空间解析解, 利用Stehfest 数值反演得到实空间的解, 进而绘制了压力和压力导数双对数样板曲线。从物理渗流机理上对曲线形态特征进行了分析并划分了流动阶段, 得出了内外区渗透率比、内区半径、窜流系数、弹性储容比等参数对这种类型油藏压力动态的影响。当内区的渗透率小于外区的渗透率时, 表现为二区压力导数曲线发生下倾; 当内区渗透率大于外区的渗透率时, 表现为压力导数上翘; 内区半径主要影响压力传播到交界处的时间; 窜流系数决定窜流段出现的早晚; 而弹性储容比影响窜流的强度和时间的长短。通过对此类典型曲线特征的分析, 为认识和改造三重介质油气藏提供了可靠的依据, 可用于研究三重介质复合油气藏渗流规律, 进行压力动态和试井分析。

Flow Model and Well Test Type Curves for Triple-Medium Reservoirs

Aimed at the polluted zone produced around a well in the course of drilling, completing and producing and the heterogeneous conditions of triple-medium carbonate reservoirs, a well test interpretation model for triple-medium composite reservoir with consideration of skin effect and wellbore storage effect is developed. Through Laplace transformation, the Laplace space analytic solution has been obtained, and converted into real space solution by means of the numerical inversion of Stehfest. The pressure and the pressure derivative bilogarithmic type curves have been drawn up. From the physical percolation mechanism, the curve shape characteristics and the flow phase are analyzed and divided, obtaining the effects of inner-and outer-zone permeability ratio, inner-zone radius, interporosity flow coefficient and storativity ratio on the pressure behavior of such a reservoir. The results indicate that when the value of the permeability of inner zone is less than that of outer zone, the pressure derivative curves of these two zones will go down. On the contrary, when the value of the permeability of inner zone is bigger than that of outer zone, the pressure derivative curves of them will go up. It is concluded that the radius of inner zone determines the time of pressure transmitting to the boundary of the outer zone; the interporosity flow coefficient determines the coming time of crossflow; the storativity ratio affects the degree and the lasting time of crossflow. These results can be used for study of percolation of tripe-medium composite reservoirs and for analyses of pressure behavior and well test.