Physical simulation experiment and numerical inversion of the full life cycle of shale gas well

Abstract

The ultra-low porosity and permeability, as well as complex occurrence and transport state of shale reservoir make it possess special L-type production characteristic curve and complicated shale gas flow mechanism. To solve the difficulty of collecting complete production data due to short production time and operation discontinuity, a full-diameter core physical simulation experiment on the full lifecycle production process of shale gas well depletion is conducted with the purpose of obtaining many important production data including complete pressure and daily gas output in the simulated production process of shale gas well. The experimental results show the production characteristic from simulation is consistent with those from gas well. Based on the simulation data, the critical desorption pressure (12 MPa) of core, free gas production (3820.8 mL), adsorbed gas production (2151.2 mL), the proportion of the daily gas production between free and absorbed gas under different time and formation pressure, as well as the production time and final recovery rate corresponding to abandoned pressure, can be determined accurately. Numerical inversion is carried out to calculate the production performance curve of shale gas well and predict the development effect of gas well based on well testing and similarity analysis of the dimensionless time between core experiment and gas well production. Finally, the permeability and the fracturing effect (fracture network density) as the keys to the effective development of shale gas reservoirs are proposed. The permeability is the fundamental factor and the fracturing technology is the major means.