毛管力对油藏水驱特征影响分析

注水开发是油田最主要的开发方式之一。注入水波及面积是影响油藏采收率的重要因素。油藏内注入水流动方向及波及面积与其所受合力的方向及大小有关。尤其对于低渗透油藏,毛管力对油藏内油水渗流规律的影响不容忽视。基于渗流力学理论,利用数值模拟和矢量叠加方法,计算了正韵律正方形储层模型中各网格内流体所受注入水压力、重力和毛管力等作用力合力的大小和方向,实现了储层内任意网格油水渗流作用力的定量表征。数值模拟结果表明,对于亲水正韵律油藏,储层上部渗透率变低使毛管力增大,当毛管力增大到一定程度时,注入水会从下部的高渗透层段向上部的低渗透层段渗流,导致上部低渗层段的水驱效果好于下部储层,在油藏开发后期剩余油主要分布在下部的高渗透层段内。如果油藏渗透率较大,油藏内无毛管力影响时,开发后期剩余油主要分布在上部的低渗透层段内,对下部高渗透层段实施封堵措施,有利于提高油藏采收率。

Analysis of the influence of capillary force on water flooding characteristic of oil reservoir

Waterflooding is one of the leading development methods of oilfield The swept area of injected water is a crucial factor affecting recovery ratio of oil reservoirs. The flow direction and swept area of the injected water in oil reservoirs are related to the direction and magnitude of the resultant force on the injection water.The previous researches show that, especially for low permeability reservoir, the influence of capillary force on the oil and water seepage law in oil reservoirs cannot be ignored. Based on the theory of dynamic of fluids through porous media, the magnitude and direction of the resultant force of pressure, gravity, capillary force and other forces on the fluid in each grid in the positive rhythm square reservoir model are calculated by using numerical simulation and vector superposition method, and the quantitative characterization of oil-water seepage force in any grid of the reservoir is realized. The numerical simulation results show that the capillary force increases with the decrease of permeability in the upper part of the hydrophilic positive rhythm reservoir. When the capillary force increases to a certain extent, the injected water will seep from the lower high permeability interval to the upper low permeability interval, resulting in a better water flooding effect in the upper low permeability interval than that of the lower reservoir, and the remaining oil is primarily distributed in the lower high permeability interval in the later stage of reservoir development. If the reservoir permeability is high and there is no capillary force in the reservoir, the remaining oil is mainly distributed in the upper low permeability interval in the later stage of development, and sealing measures are implemented in the lower high permeability interval, which is beneficial to improve the oil recovery.