低渗透裂缝性油气藏非稳态窜流因子研究简

深入分析了常定窜流因子和现有的非稳态因子对于低渗透基质-裂缝窜流的不适应问题，根据对23 个低渗岩心渗流曲线的拟合分析结果，引入了变渗透率系数，并在此基础上推导了非线性扩散方程，也就是低渗透基质-裂缝系统间窜流的控制微分方程；经过无量纲化处理，引入了动边界条件，分别利用积分方法和矩方法导出了非线性扩散方程在前后两个阶段的近似解析解，并在此基础上构建了非稳态窜流因子的表达形式；新的窜流因子可以有效应用于低渗透基质-裂缝系统间的窜流计算，有限元数值模拟的结果验证了新因子在计算非线性非稳态窜流方面的准确性与可靠性.

RESEARCH ON NONSTEADY SHAPE FACTOR OF CROSS FLOW IN LOW PERMEABILITY FRACTURED RESERVOIRS

The mass transfer shape factor between matrix and fracture is one of the most important parameters in the numerical simulation research on porous flow in fractured reservoirs. For the purpose of indicating the nonlinear and nonsteady characteristics of mass transfer between fracture and matrix in low permeability fractured reservoirs, this paper firstly analyzed the inapplicability of pseudo-state shape factor and existing nonsteady shape factor used in low permeability fracture reservoirs, then the variable coefficient of apparent permeability was introduced based on the fitting analysis results of the v-!-abla p curve of 23 core samples, and then a nonlinear diffusivity equation was developed based on the variable coefficient to govern the mass transfer between fracture and low permeability matrix. Integral method and method of moments were applied to deduce semi-analytical solution of zero dimension nonlinear diffusivity equation at the earlier and later stages, to lead the nonsteady shape factor and the new mass transfer function. By comparison with the pseudo-state mass transfer model, which was restricted to describe the mass exchange in the systems whose pressure changes quite slowly, the new shape factor was effective to simulate the nonlinear and nonsteady mass transfer between matrix and fracture in low permeability fractured reservoirs, and the fine grid finite element numerical model verified the reliability and availability of the nonsteady shape factor and the new transfer function.