Experimental investigation on the mechanism of low permeability natural gas extraction accompanied by carbon dioxide sequestration

The injection of CO2 into natural gas reservoir is regarded can increase natural gas recovery accompanied with CO2 sequestration. In this work, we first demonstrated that the gas adsorption ability in the sampled plunger low permeability sandstone core was only about 1/10 of that in the core powders, the former was more representative for use. The existence of bound water substantially weakened the gas adsorption in the core. The CO2 diffusion coefficients in low permeability cores were in the order of 10−8-10−9 m2/s, which increased with decreasing pressure but dramatically decreased with the existence of bound water. Last, long core experiments for natural gas recovery through CO2 flooding showed that the CO2 injection substantially increased the natural gas recovery ratio R. And we for the first time demonstrated that due to the higher CO2 density than that of natural gas through experiments, the CO2 injection at the relative low position showed higher R than that at the high injection position. And with the highest CO2 sequestration amount (M) reached 64.36 kg/m3. The injection of CO2 into low permeability natural gas reservoir to realize both natural gas recovery and CO2 sequestration are tested feasible and effective.