致密储层复杂流体模型及其适用性分析

致密油气储层普遍面临油气流动性低、产量不稳定的问题,对低孔渗致密储层的渗透率预测是油气勘探开发中亟待解决的问题。致密储层流体流动的关键机理不清楚,传统孔隙介质流体模型难以为渗透率预测提供足够的理论支撑,这些问题均制约了渗透率预测的准确度。针对微纳米尺度的致密储层孔隙结构,详细分析了致密储层复杂流体模型的理论基础和适用范围。不同尺度孔隙空间流动参数的数值计算和对比分析结果表明,Knudsen模型适用于较低压力下微纳米孔隙中的气体流动,对于致密储层油、水等液体或稠密气体来说,Knudsen流动的影响可以忽略;Forchheimer模型适用于孔隙介质中流体速度较高的情况,当致密储层中流体流速较低时,对流动惯性项的修正基本可以忽略。流体模型理论及其适应性分析对于深入理解致密储层复杂流动现象至关重要,研究结果为致密储层渗透率技术的应用研究提供了理论基础。

Analysis of complex fluid model and its applicability in tight reservoirs

Low oil/gas mobility and unstable production are two major problems associated with tight oil/gas reservoirs.Therefore,it is crucial to predict the permeability of low porosity oil/gas reservoirs for exploration and production.However,the mechanism of fluid flow in reservoirs with tight pores is still unclear.Traditional fluid flow models entail difficulties in providing theoretical support for predicting reservoir permeability.The theory and application conditions of complex flow models for tight reservoirs were analyzed in detail in this study.Numerical computations and analysis with different fluid parameters and pore sizes showed that the Knudsen model is suitable for gas flow in micro/nano pores at low pressure.The influence of Knudsen flow could be neglected for liquids(such as oil and water)and condensed gas in tight reservoirs.The Forchheimer model was found to be suitable for high velocity fluid flow in porous media.The correction of inertia was small and therefore could be neglected for low velocity fluid flows in tight reservoirs.The analysis of flow models and corresponding applications are important to further understand phenomena associated with complex fluid flow in tight reservoirs.The results provide strong baseline knowledge of the underlying mechanisms that can be used in the application of technology for improving the permeability of tight reservoirs.