基于天然气物性变化的低渗透气藏动态储量计算方法——以靖边气田S区为例

A method based on physical property change of natural gas to calculate dynamic reserves of low-permeability gas reservoirs: An example from S block, Jingbian gasfield

低渗透气藏在开发过程中,受应力敏感性的影响,其天然气物性随着压力发生变化。但传统的流动物质平衡法在计算动态储量建立模型时,认为天然气物性是固定不变的,这与实际生产情况不符,势必会造成计算过程中产生误差。针对这个问题,在流动物质平衡法的基础上,考虑了天然气生产过程中压力变化对天然气黏度和压缩系数的影响,推导出改进后的流动物质平衡法计算公式。给出新方法计算的方法和步骤,并在靖边气田S区进行应用。其计算结果表明:流动物质平衡法较修正后的新方法计算的动储量结果偏小,平均误差为12.84%,最大16.15%。新方法减小了流动物质平衡法的计算误差,提高了该方法计算的准确性,且计算简便,在低渗透气藏具有实用性。

Affected by stress sensitivity, some physical properties of natural gas vary with pressure during development of low-permeability gas reservoirs. When traditional flowing material balance is used to calculate dynamic reserves and establish a model, these properties are considered to be constant, which are not coincident with actual production, and many calculation errors are inevitable. So, a new calculation equation of flowing material balance method was derived from the flowing material balance method by considering the influence of pressure change on viscosity and compression coefficient. And its calculation methods and procedures were developed and applied to S block, Jingbian gasfield. It is indicated that, compared with the new method, the flowing material balance one has a smaller dynamic reserve result, with an average error of 12.84% and the maximum of 16.15%. The new method reduces the calculation error of flowing material balance method and increases the calculation accuracy. What's more, its calculation is simple and very available for low-permeability gas reservoirs.