Impacts of stratum dip angle on CO2 geological storage amount and security

Storage strata are usually generalized as horizontal when using numerical simulation methods to analyze CO2 geological storage in saline aquifers. However, horizontal strata are not common in nature. Most strata have gradients, because of the effects of geological structure and diagenesis. Based on the actual strata dip angle variation range of two CO2 injection demonstration projects in China, five modeling schemes were designed to investigate the impact of formation dip on CO2 storage amount and space migration of gas-phase CO2 in reservoir formation. The results show that the total CO2 storage amount is inversely proportional to formation dip, and after injection is halted, storage amounts of upper and lower parts of the same stratum reservoir have a reverse trend. Formation dip has a significant impact on the migration of CO2. The greater the formation dip, the more significant the effect on CO2 migration distance. Given the low porosity and permeability of the Shiqianfeng formation reservoir in the case study, when the stratum dip angle is 16 degrees, at centennial time scale, CO2 migration distance is 47.06% greater than that in the horizontal reservoir. We expect that for storage reservoirs with high porosity and permeability, the influence of formation dip on CO2 migration will be more significant. Because non-horizontal strata are predominant in deep saline aquifers in nature, regardless of the influence of formation dip, CO2 leakage risks in geological storage will be greatly underestimated. Therefore, in research related to CO2 geological storage, the stratum dip angle must be considered. (c) 2016 Society of Chemical Industry and John Wiley & Sons, Ltd