A new method to calculate the effect of fracturing fluid imbibition on adsorbed gas content for shale gas reservoir

Abstract

In-situ methane occurrence in shale gas reservoirs is seriously affected by the massive imbibed fracturing fluid. However, it is difficult to quantify the impact degree due to the complexity of pore connectivity. In this study, we firstly evaluated the ratio of through and blind pores by a proposed method firstly. Then the different influences of imbibition on gas occurrence in through and blind pores were demonstrated through designed experiments and a visual computational simulation. Finally, a new analytical model was proposed to calculate the effect of imbibition on adsorbed gas content, based on the ratio of through and blind pores and their different imbibition phenomenon. The comparison of the calculation and experimental results showed: (1) the new method can accurately predict the impact degree of imbibition on adsorbed gas; (2) imbibition in through pores leads to the co-current and countercurrent imbibition, and imbibition in blind pores leads to a compression of free gas.