用广义拟压力方法确定压敏油藏气井流入动态

Evaluation on inflow performance relationship of gas wells in pressure-sensitive reservoir using generalized pseudo pressure

杨永智 廖新维 沈平平

YANG Yong-zhi LIAO Xin-wei SHEN Ping-ping

中国石油大学, 北京 102249 中国石油勘探开发研究院, 北京 100083

为了更准确地描述压敏油藏真实气体渗流特性,通过引入广义拟压力函数来表征压敏油藏气体的渗流过程,使气体渗流扩散方程与单相微可压缩液体渗流扩散方程有相同的形式。在计算广义拟压力函数值时,首先用相应的模型计算在定温时,任意压力下气体的黏度、偏差因子以及地层渗透率的值,然后采用梯形规则,进行小步长压力计算。通过数值积分,求出定温时任一压力下广义拟压力值,回归其方程系数,得到真实气体拟压力和压力之间计算关系式,并将其用于气井流入动态的分析。结果表明,引入广义拟压力函数来描述压敏油藏真实气体渗流特性,能使气体渗流扩散方程的形式得到简化;在此基础上提出的真实气体拟压力计算方法,能使真实气体拟压力的计算快速、准确,为气井流入动态分析提供了基础,对提高压敏气藏模拟精度具有重要意义。

To precisely describe the permeability characteristics of real gas in pressure-sensitive reservoir,the generalized pseudo pressure function is introduced to characterize the gas flow in pressure-sensitive reservoir.Thus the gas seepage-diffusion equation has the same expression with the diffusion equation of the slightly compressible liquid flow with single direction.While evaluating the generalized pseudo pressure function,corresponding models can first be used to calculate the gas velocity,the deviation factors and the formation permeability under constant temperature and various pressures.Secondly,the step-size pressure is calculated according to the trapezoidal rule.Numerical integration is applied to evaluate the generalized pseudo pressure fit to a constant temperature and any pressure and regress the coefficients to the gas seepage-diffusion equation.The expression for the relation between the pseudo pressure and the pressure of real gas is obtained and then applied to analyze the inflow performance relationship of gas wells.Results show that the expression of the gas seepage-diffusion equation can be simplified by introducing generalized pseudo pressure coefficients to describe the permeability characteristics of real gas in pressure-sensitive reservoir.Then a method to calculate the pseudo pressure for real gas is proposed,which makes the calculation of more rapid and accurate.It lays a solid foundation for analyzing gas-well inflow performance relationship and is very important in improving stimulated precision of pressure-sensitive reservoir.

10.3969/j.issn.1000-7393.2007.01.030