【作者】 李涛；

【导师】 苏玉亮；

【作者基本信息】 中国石油大学 ， 油气田开发工程， 2008， 硕士

【摘要】 在我国低渗透油田中,特低渗油藏或超低渗油藏占低渗透储量的一半以上。特低渗油藏由于渗透率较低,存在启动压力梯度,给油田开发带来很大困难,同时,特低渗油藏的储层在开发过程中,要发生部分或全部的不可逆变形,会明显地影响油田的动态特征。因此,特低渗油藏渗流机理的研究具有非常重要的意义。本文推导了不可逆变形情况下,渗透率随着地层压力变化的数学表达式。考虑启动压力梯度,建立了不可逆变形条件下特低渗油藏单相非线性稳定渗流数学模型,并进行了数值求解。计算结果表明:在内边界定压条件下,渗透率下降变化系数越大,地层压力下降越缓慢,产量也随之下降,极限供油半径越小;在内边界定产量条件下,随着渗透率下降变化系数的增加,地层压力下降越快。在此基础上,建立了不可逆变形条件下特低渗油藏单相非线性不稳定渗流数学模型,并进行了数值求解。计算结果表明:在内边界定产量条件下,随着渗透率下降变化系数的增加,地层压力下降越快,井底流压越来越低,极限供油半径越大。利用特低渗油藏单相启动压力实验的结果,得到油水两相渗流启动压力梯度的数学表达式。建立了考虑启动压力梯度的一维油水两相驱替数学模型,进行了数值求解。计算结果表明:启动压力梯度的存在造成了平均含水饱和度的降低和地层压力的升高;平面非均质性的存在导致地层平均含水饱和度和地层压力降低;在平面非均质性大小分别确定的情况下,按渗透率线性增加型和先增后降型的分布方式进行驱替时,驱替效果较好。考虑特低渗油藏的储层变形特征及启动压力梯度的影响,建立一维油水两相流固耦合数学模型,进行了数值求解。计算结果表明:考虑耦合情况下,随着水驱油的不断进行,地层的渗透率和孔隙度是不断增加的;水相压力、含水饱和度和启动压力梯度相对于非耦合模型较低;地层的应变和有效应力逐渐增加。更多还原

【Abstract】 In low permeability oil field of our country, extra-low or ultra-low permeability reservoirs account for more the half, the threshold pressure gradient occurs in extra-low permeability reservoirs and brings difficulties to the oilfield development, at the same time, with the variation of the formation pressure, the formation deformation is usually non-reversible in extra-low permeability reservoirs, It will obviously affect the dynamic characteristics of oilfield. So the flow mechanism research of extra-low permeability reservoir is very important.By developing the connection that permeability varies with the pressure drop in this paper, the non-linear steady flow model is established accounting for non-reversible deformation, and which is sovled with numerical method. Under the condition of constant pressure , the results show that the formation pressure decreases more and more slowly with the permeability drop variation coefficient increasing, the oil production and limit control radius decreases; when the oil production is constant, the formation pressure decreases more and more quickly with the permeability drop variation coefficient increasing; on this basis, the non-linear nonsteady flow model is established accounting for non-reversible deformation, and which is sovled with numerical method, when the oil production is constant, the results show that the formation pressure decreases more and more quickly with the permeability drop variation coefficient increasing, the bottom hole flowing pressure decreases, and limit control radius increases.Based on the treshold pressure gradient study of single phase on extra-low permeability reservoir, we can obtain oil-water two-phase treshold pressure gradient. One-dimension water-oil displacement mathematics model considering threshold pressure gradient is established. By means of numerical solution, computational solution indicates that threshold pressure gradient causes average water saturation rising and formation pressure decreasing; permeability areal heterogeneity causes average water saturation and formation pressure decreasing; on the base of areal heterogeneity dimension is confirmed, when displacing by linear rising mode and firstly rising then decreasing mode, displacement efficiency is better.The one-dimension water-oil displacement and fluid-structure coupling mathematics model is established accounting for deformation characteristic and treshold pressure gradient, and which is sovled with numerical method. Computational solution indicates that porosity and permeability increases under fluid-structure coupling conditions; with respect to non-coupling model, water phase pressure, water saturation and treshold pressure gradient are lower; the formation strain and effective stress increases continuously.更多还原