Experimental study on imbibition effect of columnar raw coal containing gas under water-thermal coupling action

Abstract

In order to investigate the characteristics of water displacement and adsorption of gas along the original cracks and pores of coal under the action of water-thermal coupling, imbibition experiments of 50 mm×100 mm columnar raw coal were carried out for 240 h at 20 ℃, 40 ℃, 60 ℃ and 80 ℃ under the initial equilibrium gas pressure of 0.5 MPa, 1.0 MPa, 2.0 MPa and 3.0 MPa. Experiments show that: high temperature can significantly improve the efficiency of water imbibition replacement for methane. Under the initial low pressure of 0.5 MPa, the imbibition replacement rate(240 h) at 80 ℃ is 1.6 times higher than that at 20 ℃, increasing to 57.21%; the displacement rate(240 h) and imbibition constant at the same pressure increased with the increase of the experimental temperature, while the displacement rate(240 h) and imbibition constant at the same temperature decreased with the increase of the initial pressure; the imbibition displacement efficiency at low pressure was higher than that at high pressure at the same temperature, and high pressure would inhibit the imbibition displacement effect; the water imbibition displacement efficiency is higher in the low-temperature environment, so it is not suitable to directly inject heat(water) in the high-pressure reservoir; the gas recovery rate should be further improved by reinjecting heat(water) when the driving force of low-pressure gas is insufficient.

Keywords

• heat injection
• imbibition effect
• columnar raw coal
• imbibition constant
• replace rate
• recovery rate