Porosity evolution of Minhe oil shale under an open rapid heating system and the carbon storage potentials

The ideal non-collapse heated oil shale reservoir may lead to the maximum preservation of pores and fractures. However, the previous research on the pore evolution during heating in oil shale reservoirs has focused only on the analysis of capillary pores, ignoring the supercapillary pores (including fractures) that can provide the free flow of fluid. Through open thermal system experiments, combined with multi-scale visual statistics and quantitative testing, this paper reveals that the surface porosity of supercapillary pores increased from 0.27% to 15.95% and the porosity of capillary pores and microcapillary pores increased from 0% to 39.55%, in which the contribution rate of organic matter pores increased from 2.36% to 87.46%. From the perspective of the trap, we propose that the displacement pressure, breakdown pressure and overburden pressure of surrounding rock determine the pressure of injected CO ₂. Regarding the adsorption and free state, through an improved formula for carbon storage potentials, the maximum theoretical CO ₂ storage per unit volume for the Minhe depleted oil shale reservoir was estimated to be approximately 0.261 × 10 ⁹ t/km ³. Thus, a depleted oil shale reservoir is a suitable place for CO ₂ storage owing to the large storage potential.