Experimental Investigations of the Impact of H2, He, CH4, and CO2 Exposure on Kerogen Adsorption, Wettability, and Geomechanical Characteristics at Geo-Storage Conditions

Summary Kerogen is the most abundant form of organic matter in the subsurface and its properties of adsorption, wettability, and geomechanics affect gas (H2, He, CH4, and CO2) geo-storage (GGS) capacity and leakage risk. However, the impact of H2, He, CH4 and CO2 exposure on kerogen adsorption, wettability and geomechanical characteristics at in-situ GGS conditions is still unclear, and thus large uncertainties exist in evaluating on GGS integrity. Therefore herein, kerogen properties were investigated experimentally at GGS conditions, based on isothermal adsorption, contact angle, and nanoindentation measurements. It is demonstrated that (1) the maximum adsorption capacity for H2, CH4, and CO2 is 0.3789, 3.5360, and 5.2625 mol/kg, respectively (occurring at various thermophysical conditions), thus following the order H2 < CH4 < CO2; (2) kerogen wettability ranges from weakly water-wet to gas-wet with its affinity to gases following the order He < CO2 < H2 < CH4; and (3) after exposure to H2, He, CH4, and H2O for 3 minutes and to liquid CO2 for 5 minutes, the Young’s modulus of kerogen decreases by 45, 32, 1, 50, and 70% respectively, while the kerogen pellet disintegrates after exposure to supercritical CO2 for 3 minutes. This study provides key data for evaluating GGS, an important pathway for accelerating the energy transition, promoting advanced technology development, balancing the energy supply and demand, and mitigating carbon emissions.