Impact of Injection Velocity on Wormhole Generation Due to CO2 Sequestration

Abstract

Abstract Carbon dioxide (CO2) could be potentially stored in deep saline carbonate aquifers, taking advantage of its solubility in brine. Nevertheless, wormholes will be created due to the reactivity of carbonic acid with limestone. This research targets revealing the impact of live brine (i.e., sc-CO2 soluble in brine) injection velocity on the efficiency and shape of generated wormholes. Core samples of limestone, measuring 1.5 × 3 inches and exhibiting permeability values ranging from 2 to 3 mD, along with porosity values ranging from 15 to 17%, were chosen for the study. Following the coreflooding experiments, the samples underwent scanning to observe both the generation of wormholes and alterations in the pore structure. CO2 was mixed with 120,000 ppm salinity brine at 60 °C and 2,000 psi at a 30:70 ratio and injected into the core samples. The effect of injection velocity was analyzed by injecting live brine at 0.25, 1, and 5 cc/min. 700 mL of CO2-saturated brine were injected for all the experiments. The analysis showed a porosity increase due to the creation of wormhole from the injection of live brine. A significant increase has been seen in permeability due to created half or continuous wormholes. Furthermore, as the injection increased from 0.25 cc/min to 1 cc/min, less live brine was needed to create the wormhole. On the other hand, the increase in flow rate from 1 to 5 cc/min siginificantly increased the required volume. These results indicated an optimum injection velocity to be at 1 cc/min with the PVBT of 18. In summary, the study revealed that the injection of live brine induces the formation of a wormhole, resulting in changes to the porosity and permeability of the rock. The novelty of this study lies in its application to CO2 storage, specifically in exploring the influence of injection rate on the sequestration process. This study marks the pioneering effort to comprehend the impact of CO2 injection velocity on wormhole generation and to identify the optimal conditions for such processes.