Gas Displacement Engineering Test by Combination of Low and Medium Pressure Injection with Liquid CO2 in High Gas and Low Permeability Coal Seam

Abstract

Mining high-gas coal seams in China has the characteristics mining of deep, high storage and low permeability, and low drainage efficiency, which seriously restrict the efficient prevention and control of mine gas disasters. Based on the characteristics of low viscosity and permeability, phase change pressurization, and strong adsorption potential energy of liquid CO2, the technology system of liquid CO2 displacement for high-gas and low-permeability coal seam was developed, and field industrial of low-pressure (0.5~2.5 MPa) and medium-pressure (2.5~15.0 MPa) combined injection test was carried out. In this test, the mode of injection followed by drainage was adopted, and the gas drainage effect was investigated for 30 days. The test results show that the effective influence radius of CO2 in this test is 20 m, and the liquid seepage radius is 5 to 7 m. After the injection of liquid CO2 into coal seam, the average gas drainage concentration and drainage purity of all drainage holes were increased by 3.2 and 3.4 times, respectively, and the gas promotion effect was significant. Taking the liquid CO2 low-medium-pressure displacement gas test area as the calculation unit, from the comprehensive benefit analysis, compared with the original drainage mode, the liquid CO2-combined pressure injection process can save 34.7% of the engineering cost and shorten the gas drainage standard time by 45.9%. Therefore, the application of this technology has important technical support and reference significance for the efficient management of gas in the same type of mine.

Experimental Investigations on Enhanced Coal Seam Methane Extraction by Injecting Gas: A Review

“…Wen et al 94 used the self-developed technology and equipment of liquid CO 2 displacement in the low permeability coal seam to carry out engineering experiments of CO 2 injection under low pressure (0.5−2.5mpa) and pressure (2.5−15.0 MPa). The results show that the LCO 2 injection process can effectively save 34.7% of the project cost and shorten 45.9% of the extraction standard time.…”

“…Wen et al 94 developed a liquid CO 2 drive and displacement system for high gas and low permeability coal seams, which was composed of liquid data acquisition instrument (DAI),…”

“…Process diagram of liquid CO 2 injection system: (a) transportation equipment, (b) cryogenic power pump, (c) field application, and (d) liquid CO 2 injection system. Reproduced with permission from ref . Copyright 2020 Hindawi.…”

Experimental Study of CO2-ECBM by Injection Liquid CO2

“…The data acquisition system includes pressure acquisition, flow acquisition, and drainage system monitoring (drainage flow, CO 2 concentration, and CH 4 concentration). The gas extraction system includes a gas extraction pump and extraction pipeline [40,41]. When the booster pump was used, the pipeline of the injection system was pre-cooled, and the temperature condition of the pump start was set to ≤−15 • C. In order to ensure that CO 2 was kept in the liquid state during the injection process, the pressure of the booster pump was never less than 3.0 MPa.…”

Characteristics of Pressure Relief Gas Extraction in the Protected Layer by Surface Drilling in Huainan

“…e field results show that the technology has a significant effect on coal reservoir reconstruction and coal seam methane recovery, but the range of influence is small. Wen et al [16][17][18][19][20][21][22][23][24] proposed liquid CO 2 permeability enhancement and gas displacement technology in coal mines, carried out several underground engineering tests, and achieved good results. However, these studies had problems such as small test areas and difficulty of CO 2 transportation.…”