Estimated Ultimate Recovery and Productivity of Deep Shale Gas Horizontal Wells

Pressure control in deep shale gas horizontal wells can reduce the stress sensitivity of hydraulic fractures and improve the estimated ultimate recovery (EUR). In this study, a hydraulic fracture stress sensitivity model is proposed to characterize the effect of pressure drop rate on fracture permeability. Furthermore, a production prediction model is introduced accounting for a non-uniform hydraulic fracture conductivity distribution. The results reveal that increasing the fracture conductivity leads to a rapid daily production increase in the early stages. However, above 0.50 D·cm, a further increase in the fracture conductivity has a limited effect on shale gas production growth. The initial production is lower under pressure-controlled conditions than that under pressure-release. For extended pressure control durations, the cumulative production initially increases and then decreases. For a fracture conductivity of 0.10 D·cm, the increase in production output under controlled-pressure conditions is ~35%. For representative deep shale gas wells (Southern Sichuan, China), if the pressure drop rate under controlled-pressure conditions is reduced from 0.19 to 0.04 MPa/d, the EUR increase for 5 years of pressure-controlled production is 41.0 million, with an increase percentage of ~29%.