分形拟三重介质致密油藏产能预测模型

致密油藏渗流机理复杂、产能预测难度大。文中引入分形理论,推导出基质、天然微裂缝、人工裂缝的分形孔隙度和分形表观渗透率。建立了考虑启动压力梯度及压敏效应的分形拟三重介质致密油藏数学模型,推导出模型压力解与动态供给边界的变化情况。在此基础上,建立了产能预测模型,结合实例数据完成模型验证,进行供给半径和产能的动态预测,并对非线性渗流参数进行敏感性分析。结果表明:供给半径随时间非线性增加,同一时刻,启动压力梯度及分形系数越大,供给半径越小;分形致密油藏产能受非线性渗流参数的影响,启动压力梯度越低,变形系数越小,分形系数越小,则日产量越高,反之日产量越低。

Productivity prediction model of fractal pseudo-triple medium tight oil reservoirs

In tight oil reservoir,it is difficult to study the percolation mechanism and productivity prediction.However,fractal theory provides a method to describe the complex system.Therefore,this paper introduces the fractal theory to deduce matrix,natural micro fractures,artificial fractures' fractal fracture porosity and fractal apparent permeability.The mathematical model of the pseudo-triple medium tight oil reservoir with the starting pressure gradient and the stress sensitive effect was established.The pressure solution of the model and the change of the radius of the oil discharge were derived.On the basis of the above,the productivity prediction model was established.Combined with the field data,the fractal model presented in this paper was verified.After that,supply radius and production were predicted.Finally,nonlinear parameter sensitivity analysis was conducted.The results show that with the increase of time,the supply radius increases nonlinearly.At the same time,the larger the starting pressure gradient and fractal coefficient are,the smaller the supply radius is;nonlinear parameters have a great effect on production of fractal tight oil reservoirs.The lower the starting pressure gradient is,the smaller the deformation coefficient is;the smaller the fractal coefficient is,and the higher the daily output is.