Numerical Simulation of Shale Gas Multiscale Seepage Mechanism-Coupled Stress Sensitivity

Abstract

The complexity of the gas transport mechanism in microfractures and nanopores is caused by the feature of multiscale and multiphysics. Figuring out the flow mechanism is of great significance for the efficient development of shale gas. In this paper, an apparent permeability model which covers continue, slip, transition, and molecular flow and geomechanical effect was presented. Additionally, a mathematical model comprising multiscale, geomechanics, and adsorption phenomenon was proposed to characterize gas flow in the shale reservoir. The aim of this paper is to investigate some important impacts in the process of gas transportation, which includes the shale stress sensitivity, adsorption phenomenon, and reservoir porosity. The results reveal that the performance of the multistage fractured horizontal well is strongly influenced by stress sensitivity coefficient. The cumulative gas production will decrease sharply when the shale gas reservoir stress sensitivity coefficient increases. In addition, the adsorption phenomenon has an influence on shale gas seepage and sorption capacity; however, the effect of adsorption is very weak in the early gas transport period, and the impact of later will increase. Moreover, shale porosity also greatly affects the shale gas transportation.

A Comprehensive Model for Estimating Stimulated Reservoir Volume Based on Flowback Data in Shale Gas Reservoirs

“…Therefore, the gas-water saturation in the fracture system can be established as a function of gas-water production with time. Given the characteristics of abnormal overpressure in this area, the stress sensitivity in this area cannot be ignored [36,54,55]. Therefore, the stress-sensitive model was considered in the dynamic relative permeability function.…”

“…It may be due to the inaccuracies caused by stress sensitivity in some areas. In particular, there is abnormal overpressure in shale gas reservoirs in southern China [35], so the influence of stress sensitivity, especially for the two-phase relative permeability, has to be taken into account [36]. Moreover, all the researchers did not make a production data verification and comparison with the microseismic data.…”

Pore-scale study of non-ideal gas dynamics under tight confinement considering rarefaction, denseness and molecular interactions

“…The equation of state (EOS) of real gases, such as the van der Waals, Soave-Redlich-Kuang and Peng-Robinson, is commonly used to account for the non-ideal gas effect when studying gas flow behaviors in natural gas reservoirs [5][6][7]. Comparing to the ideal gas EOS, gas molecule size and molecular interaction are taken into account in the real gas EOS.…”