特低渗透油藏CO_2非混相驱井距与产量关系理论模型

Theoretical model for relationship between well spacing and oil production by CO_2 immiscible flooding in the extra-low permeable reservoir

依据预期产量建立井距模型对于确定合理井网密度具有重要意义。基于特低渗透油藏非线性渗流理论,考虑CO_2对原油的降黏作用及油相启动压力梯度变化,建立了一维CO_2非混相驱渗流数学模型。在此基础上,应用Buckley-Leverett驱替理论和渗流理论,建立了特低渗透油藏CO_2非混相驱井距与产量关系理论模型,开发了井距计算软件并进行了实例计算和理论图版绘制。结果表明,考虑油相黏度、油相启动压力梯度均变化时,井距最大;在驱替前期,油相启动压力梯度对井距的影响显著,而油相黏度对井距的影响较小,在驱替后期油相黏度对井距的影响逐渐变强;井距随预期产量的增加而减小,预期产量越小,井距增长得越快;井距随地层原油初始黏度、油相初始启动压力梯度的增加而减小。井距与产量关系理论模型给出了一种依据预期产量计算井距的快速计算方法,为油田井网部署提供了理论依据。

Establishment of well spacing model according to the anticipated oil production has important significance to determine reasonable well spacing density.Based on non-linear seepage theory of extra-low permeable reservoir,consideringthe effect of CO2to reduce oil viscosity and the oil phase starting pressure gradient change,one-dimensional mathematical model for the seepage by CO2immiscible flooding was established.By the application of Buckley-Leverett displacement theory and seepage theory,the theoretical model for the relationship between well spacing and oil production by CO2immiscible flooding in the extra-low permeable reservoir was built and the well spacing calculation software was developed for the example calculation and theoretical chart drawing.The results show that the well spacing is maximum with consideration of both viscosity and starting pressure gradient changes of the oil phase.In the early stage of displacement,the oil phase starting pressure gradient has significant effect on the well spacing while oil phase viscosity has small effect on the well spacing.In the later stage of the displacement,the effect of the oil phase viscosity on the well spacing has gradually become stronger.Well spacing becomes smaller with the increase of the anticipated production.The less the anticipated production becomes,the faster the well spacing increases.The well spacing becomes smaller with the increase of the initial viscosity of the formation oil and initial starting pressure gradient of the oil phase.Moreover,the theoretical model for the relationship between well spacing and oil production has offered a rapid calculation method for the well spacing calculation on the basis of anticipated production and provides the criteria for the well network deployment in oilfield.