A dynamic prediction model of pressure-control production performance of shale gas fractured horizontal wells and its application

Abstract

For clarifying the inherent relation between relieving fracture closure and improving the EUR by adopting the pressure-control production system for shale gas fractured horizontal wells, and the significance of pressure-control production for gas reservoir engineering, a dynamic formation–fracture coupling prediction model for production performance of fractured horizontal wells was established and solved, with the finite conductivity fracture as basic flow unit and the variable stress sensitivity coefficient introduced. Through a comparison of the calculated results from the established model, classical model and numerical modeling by the Saphir software, the effect of characteristic parameters of stress sensitivity and pressure-control production system on the production performance of fractured horizontal wells was analyzed and verified in two wells. The results show that (1) the calculated results from the established model are basically consistent with those from the classical model and the numerical modeling by the Saphir software; (2) the existence of stress sensitivity makes the fracture conductivity decline with the production of gas wells, which leads to the decrease of cumulative gas production; the greater the stress sensitivity, the greater the decrease of cumulative gas production; (3) although the initial gas production and cumulative gas production of shale gas gained by the pressure-control production system are low compared with those by the pressure-release production system, the ultimate cumulative gas production is higher. Thus, it is more reasonable to adopt a long-term pressure-control production system for shale gas fractured horizontal wells. In conclusion, the research results provide a theoretical support for the popularization of pressure-control production system of shale gas wells. Keywords: Shale gas, Fractured horizontal well, Pressure-control production, Variable stress sensitivity coefficient, Non-linear flow, Initial gas production, Ultimate cumulative gas production