基于Hiles and Mott渗流模型的有界储层产量递减模型

Research and application of production decline model for bounded reservoir based on Hiles and Mott’s mechanism

根据油气井实际生产过程中普遍存在近似先定产降压、再定压降产的生产特征,开展在有界储层拟稳态阶段改用定压生产模式的产量递减模型研究,为明确油气井产量递减的渗流机理提供一种新的理论依据。依托Hiles and Mott模型,通过理论推导建立了有界储层在拟稳态阶段定压生产的产量递减模型。结果表明:该模型形式上与Arps递减模型具有一致性,但相比Arps产量递减模型,该模型更具一般性,即当Hiles and Mott指数为1时,流体渗流遵循达西定律,拟稳态阶段改变生产方式为定压生产情况下,油气井产量递减遵行指数递减;当Hiles and Mott指数在0.5~1区间时,流体渗流表现为高速非达西渗流,递减模型为幂律递减;当Hiles and Mott指数为0.5时,遵行直线递减模型;当Hiles and Mott指数大于1时,流体渗流为非达西低速渗流条件下,产量递减模型转化为双曲递减模型,并且用Arps形式表征的3个参数之间具有非线性相关性,且满足质量守恒定律,特别是当Hiles and Mott指数趋于无限大时,油气井产量递减模型无限接近于Arps递减模型的调和递减。这就为有界储层采用Arps递减模型开展油气井动态诊断赋予了渗流机理解释,解释了Arps递减模型质量不守恒和调和递减累计产量模型无界性的原因,对深入与扩展Arps产量递减模型的应用具有重要理论意义,也为利用产量递减模型开展储层参数反演提供了科学依据。

According to the common production characteristics in the actual production process of oil and gas wells,the production decline model under the change of constant pressure production mode to the quasi-steady state of bounded reservoir is studied,which provides a new theoretical basis for defining the seepage mechanism of oil and gas well production decline.Based on Hiles and Mott’s mechanism,through theoretical derivation,a new production decline model is established when the bounded reservoir reaches quasi-steady state in the late stage of boundary flow,under the condition of a constant pressure production.The results show that the model is formally consistent with Arps’decline model,and its three decline parameters have exponential correlation.However,compared with Arps’production decline model,this model is more extensive and general.That is,when the exponential coefficient from Hiles and Mott’s constitutive equation is 1,which means fluid seepage follows Darcy’s law,the production decline of oil and gas wells follows exponential decline,with the condition of pseudo steady state,because of boundary effect.When the exponential coefficient from Hiles and Mott’s constitutive equation varies between 0 and 1,the fluid is in the transitional state of Darcy flow and turbulence,and the decline curve is a power function decline,and specially when the exponential coefficient from Hiles and Mott’s constitutive equation is 0.5,which means the fluid is in a turbulent state,and the production decline curve of oil and gas wells is a straight line.When the exponential coefficient is greater than 1,which means fluid seepage is low-speed non Darcy flow,the production decline becomes a hyperbolic decline curve,and the three characterization parameters of hyperbolic decline have nonlinear correlation,and the decline model satisfies the law of mass conservation.This not only lays a theoretical foundation for the analysis and discrimination of fluid seepage characteristics in the quasi steady state stage of bounded reservoir,but also provides a scientific basis for reservoir parameter inversion using production decline model,which is of great significance for deepening and expanding the application of Arps’production decline model,so it has strong practicability and foresight.