低渗透均质油藏非达西渗流的产量动态规律

DYNAMIC RULES OF PRODUCTION OF NON-DARCY FLOW IN LOW PERMEABLE AND HOMOGENEOUS RESERVOIR

由于低渗透油藏存在非达西渗流机理，因此目前采用基于达西渗流理论的产能预测结果与实际存在较大的误差。基于低速非达西渗流理论，建立了考虑启动压力梯度的低渗透均质油藏产量变化数学模型，油藏外边界考虑了无限大、定压和封闭三种条件，应用Laplace变换方法求解得到了该模型在Laplace空间的解，采用Stehfest数值反演算法，绘制了三种外边界条件下产量和累计产量变化的理论曲线；讨论了启动压力梯度、边界距离对产量的影响规律，对比分析了非达西渗流与达西渗流产量动态变化规律的差别。研究表明：与达西渗流相比，由于启动压力梯度的存在，导致产量下降速度加快，累计产量下降。

Since non-Darcy flow mechanism exists in low permeable reservoir, production prediction results obtained by Darcy flow theory have much difference from actual results at present. On the basis of low-ratio non- Darcy flow theory, production variety mathematical model of low permeable and homogenous reservoir considering kickoff pressure gradient is established, and three conditions including infinite, finite pressure and sealing are considered for outside boundary of reservoir. Results of this model in Laplace space are determined by application of Laplace transformation method. Theory curve of production and cumulative production variety in the case of a- bove three boundary conditions is described by Using Stehfest numerical inversion method. In addition, the effect of kickoff pressure gradient and distance to boundary on production is discussed, and differences of production dynamic variety rules between non-Darcy flow and Darcy flow are analyzed. Study shows that, compared with Darey flow, production declines rapidly and cumulative production also decreases due to the presence of kickoff pressure gradient.