川西重复压裂气井应力场分析

STRESS FIELD ANALYSIS OF REFRACTURING GAS WELL IN SICHUAN WESTERN AREA

针对压裂气井生产过程中增产能力逐渐降低的问题,基于应力场分布的理论,结合川西地区的现场地质资料,建立了井筒及裂缝周围应力场分布的流固耦合模型,对气井生产的整个过程进行了仿真,分析了应力场转向范围和孔隙压力等随时间的变化规律,研究了重复压裂时机的选择。结果表明,孔隙压力随时间的推移而降低,孔隙压力改变范围不断增大;可根据计算出的应力转向范围与时间的拟合曲线选择重复压裂的最佳时机。为明确应力转向范围、判断是否实施改向重复压裂和选择重复压裂时机提供了直观可视的分析方法,具有很深的现场指导意义。

A model of coupling the stress equilibrium and fluid continuity equations was proposed to aim at production increasing ability gradually reduced in the process of fracturing gas well production. Based on the Sichuan Western area's geological data, the process of production was simulated to study the change rule of stress field and pore pressure with time. And it also helped to choose appropriate refracturing time. The results showed that the pore pressure reduced and the stress field change range expanded as time goes on. The fitting curve of stress field change range and time helped us to choose appropriate refracturing time. These methods were used to clear the change range of stress field and judge whether implement redirection fracturing. The obtained conclusions were significance for the field operation of refracturing.