Pressure Drawdown Management Based on Multi-Zone Pressure Decline Behavior in Shale Reservoir by Physical Experiments

Abstract

Abstract. Shale gas reserves are quite abundant worldwide. However, reservoir permeability and fracture conductivity will reduce severely with the rapid pressure decrease due to the stress effect, ultimately impacting the estimated ultimate recovery. However, experimental studies on pressure drawdown management and permeability variations based on deep shale have been rarely reported. To fill this gap, the integrated and innovative experimental methods are proposed to measure the influence of different pressure drawdown strategies (aggressive, moderate, or conservative) on permeability characteristics and pressure decline behavior. In this study, reservoirs near to the wellbore are divided into three distinct zones: the propped fracture zone (PF), the unpropped fracture zone (UF), and the matrix zone (M). These zones are represented by three different core samples. First, stress sensitivity experiments of PF, UF, and M cores are established to quantify the influence of effective stress on permeability. Then, a pressure drawdown management experiment of PF–UF–M multi-zone is established to investigate the relationship between the pressure drawdown strategy and production, further analyzing the loss of permeability under different strategies. The experimental results under different pressure drawdown strategies show that under the aggressive strategy, the permeability loss of each core is the most significant. The cumulative gas production under the conservative strategy increased by 5.6% compared to that of the moderate strategy, and by 12% compared to that of the aggressive strategy. This study shows the profound influence of stress effects on shale gas reservoir production. It offers theoretical and technical insights for refining shale gas development strategies.