Experimental study of the characteristics of gas-injection barrier in two-dimensional porous media

摘要

The inflow of groundwater into the oil shale in-situ pyrolysis zone reduces the heating efficiency and has negative impacts on soil ecology and drinking water safety. Thus, we propose a sealing system for oil shale in-situ pyrolysis exploitation with a gas-injection barrier. In this study, the characteristics of gas-injection barrier were investigated comprehensively in the two-dimensional porous media. First, the evolution and distribution of hydraulic conductivity were studied. Results showed that gas injection promoted water flow in the central subregion when the gas flow rate was less than 50 mL/min. With a further increase in the gas flow rate, a significant inhibition effect on the water flow within all subregions was achieved. Then, the gas-injection barrier mechanism was quantitatively analyzed, showing that a pressure-balanced state in the extended front of the upstream gas flow served as one mechanism when a larger gas flow rate was reached, which was verified by experiments for the first time. Finally, the distribution of the gas flow fitted by a Gaussian curve was explored. In addition, the sensitivity of hydraulic conductivity was discussed; with increasing water flow rate and the coarsening of glass beads, the relative hydraulic conductivity improved comprehensively. All results obtained are conducive to a comprehensive understanding and application of the gas-injection barrier.