特低渗透油藏非线性渗流数值模拟

Numerical simulation of the nonlinear flow in ultra-low permeability reservoirs

中国石油探明储量和未动用储量中特低渗透储量占很大的比例,迫切需要对特低渗透多孔介质中非线性渗流规律进行深入研究。根据特低渗透油田储集层岩心特征和流体渗流特征,建立了特低渗透油藏流体渗流的非线性渗流模型,依此建立了特低渗透油藏非线性渗流数值模拟的数学模型,并研制了相应的特低渗透油藏数值模拟软件。利用所研制的特低渗透油藏数值模拟软件,对榆树林特低渗透油田树322区块进行数值模拟计算,研究表明:拟线性渗流只发生在井口附近的局部小区域内,而在地层内部相当大的区域内是非线性渗流,非线性渗流占据了地层渗流的主导地位。因此,考虑非线性渗流比以往只考虑线性渗流以及考虑拟启动压力梯度的方法更适合特低渗透油田。

At present,ultra-low permeability reserves occupy a very large proportion in the proved and undeveloped reserves in China.So,it is necessary to research the law of the nonlinear porous flow in low permeability reservoirs.In this paper,on the basis of characteristics of low permeability formation and seepage flow mechanics in ultra-low permeability reservoirs,a nonlinear flow model which can better describe the characteristics of low permeability reservoirs is established.Based on this mathematical model,a new nonlinear mathematical model of numerical simulation is proposed.And by using the developed numerical simulation software of ultra-low permeability reservoir,the Shu 322 block in the Yushulin ultra-low permeability field is studied by means of numerical reservoir simulation.It is showed that pseudo-linear seepage flow only took place in a small range around the wellhead while nonlinear seepage flow dominated in a large scale of the formation.Therefore,taking nonlinear seepage flow into account is more suitable than only considering linear seepage flow and pseudo-startup pressure gradient.