致密性气藏压力扰动传播规律

RESEARCHES ON THE PROPAGATION OF THE PRESSURE DISTURBANCE IN TIGHT GAS RESERVOIRS

气藏压力扰动传播规律反映气井周围储层有效动用范围,是分析气井生产数据的理论基础。基于动边界思想,将压力扰动外边缘视为探测边界,运用积分方法求解了气体不稳定渗流数学模型,得到了变产量条件下压力分布及探测边界传播规律的近似表达式。对近似解作理论分析:计算不同工作制度下井底流压和流量,与经典解良好的拟合结果验证了近似解的合理性;计算探测边界内地层所提供流量占井筒流量的比例,超过90%的供给比例保证了在探测边界内使用物质平衡方程的可靠性。算法适用于气井变产量生产,引入物质平衡时间后可以获得探测边界移动规律,结合物质平衡方程能够对气井的不稳定生产数据进行解释分析。

The propagation laws of the pressure disturbance in a gas reservoir can reflect the effectively developed range of the reservoirs around the gas wells and moreover are the theoretical basis of analyzing the production data of the gas wells. Based on the idea of moving boundary, the outside edge of the pressure disturbance is regarded as the boundary of the investigation, the solutions of the mathematical model of non-linear unsteady flow for the gas are obtained by means of integral method and then the approximate expressions of the pressure distribution and propaga- tion laws of the investigated and explored boundary are achieved under the conditions of the variable production rate. The theoretical analyses on the approximate solutions are conducted, the bottomhole pressure and flow rate are calculated in different working systems, the much better matched results with the classical solutions prove that the former solutions are rational; through computing the proportions of the flow rate from the formations within the in- vestigated boundary to the borehole flow rate, over 90% supplied proportion ensures the reliability of the adoption of the material balance equation （MBE） within the boundary. The algorism stated in the paper is feasible to the variable production operation of the gas wells, after introducing the material balance time, the moving laws of the investigated boundary are achieved. In addition, integrating with MBE, the unstable production data can be ana- lyzed and interpreted for the gas wells.