页岩油藏逆向渗吸的最大渗吸动用距离计算方法

Calculation Method of Maximum Imbibition Distance of Countercurrent Imbibition in Shale Reservoirs

渗吸是页岩油藏压裂开发的重要机理,最大渗吸动用距离是渗吸动用范围评价的直接指标,对页岩油藏开发具有重要意义。为确定页岩油藏最大渗吸动用距离,在表征页岩油藏毛细管力曲线基础上,运用渗流理论、数值计算方法,建立了页岩油藏逆向渗吸最大渗吸动用距离计算方法,通过与室内实验结果进行对比,验证了计算方法的可靠性,同时开展了最大渗吸动用距离影响因素分析。研究表明:随着渗透率增加,最大渗吸动用距离呈线性增加,但达到最大渗吸动用距离所用时间呈指数降低;油水黏度比对最大渗吸动用距离无影响,但原油黏度越大,达到最大渗吸动用距离所需时间越长;当储层渗透率为0.05 mD、接触角为45°、界面张力为50 mN/m时,最大渗吸动用距离为2.2 m,所需时间为170 d,用时较长。该研究可为页岩油藏渗吸动用范围评价提供借鉴。

Imbibition is an important mechanism for fracturing development in shale reservoirs,and the maximum imbibition distance is a direct indicator for evaluating the scope of imbibition,which is of great significance for the development of shale reservoirs.In order to determine the maximum imbibition distance of shale reservoirs,a calculation method of imbibition distance of countercurrent imbibition in shale reservoirs was developed according to the principles of filtration theory and numerical methods and based on the characterization of the capillary curve of shale reservoirs.The results were compared to the results of laboratory experiments so as to verify the reliability of the calculation method and analyze the influencing factors of the maximum imbibition distance.The research shows that the maximum imbibition distance increases linearly with the increase of permeability,but the time required to reach the maximum imbibition distance decreases exponentially;the ratio of oil/water viscosity has no effect on the maximum imbibition distance,however,the greater the viscosity of crude oil,the longer the time required to reach the maximum imbibition distance;when the reservoir permeability is 0.05 mD,with the contact angle of 45°and the interfacial tension of 50 mN/m,the maximum imbibition distance is 2.2 m,taking 170 d,which takes longer time.This study provides reference for evaluating the range of imbibition distance in shale reservoirs.