Study on Seepage Characteristics and Capacity Evaluation of Shale Gas Reservoirs

Abstract

The formation, storage and seepage characteristics of shale gas reservoirs are significantly different from those of conventional oil and gas reservoirs, and their in-depth study is extremely important for improving energy security and promoting sustainable development. In this paper, based on the nonlinear seepage theory of shale gas reservoirs and the capacity analysis of test wells, a steady state capacity model integrating the apparent permeability model and the multi-scale transport mechanism is constructed to investigate the influence of various factors on the apparent permeability and the capacity of shale gas fractured horizontal wells, as well as to predict the production of shale gas wells. It is found that: apparent permeability is significantly affected by pore radius, and the non-Darcy effect is particularly significant under low-pressure and small-scale pore conditions; when the reservoir pressure is lower than 15 MPa, the sensitivity of apparent permeability to temperature and Langmuir volume increases, but decreases with the increase of Langmuir pressure; and the production capacity analysis of shale gas reservoirs shows that the production rates of fractured wells that consider the multiscale transport mechanism are generally higher than those considering Darcy flow only, especially in the case of low wellbore pressure and large pore radius; the effects of Langmuir volume and pressure on the production capacity are relatively small, and mainly noticeable in the range of wellbore flow pressure from 1 MPa to 15 MPa. The number of fracture bars has a significant effect on production, but too many fractures can lead to gap interference, which slows down production growth. The results of this research provide theoretical support for the scientific development of shale gas reservoirs and have important research and application value for the efficient and rational development of actual well sites.