Alternating N2gas injection as a potential technique for enhanced gas recovery and CO2storage in consolidated rocks: an experimental study

The promotion of enhanced gas recovery (EGR) and CO(2)storage is still shrouded in contention and is not well accepted, due to the excessive in situ CO(2)mixing with the nascent natural gas. This adulterates the recovered CH(4)and thus results in a high sweetening process cost thereby making the technique impractical. This has not only limited the field application of EGR in actual projects to a few trails but renders it uneconomical. This study aims to present, experimentally, alternating N(2)injection as a potential technique for EGR and CO(2)storage in sandstone rock cores. A laboratory core flooding experiment was carried out to simulate a detailed process of unsteady-state methane (CH4) displacement using Bandera grey core plug. This was carried out at 40 degrees C, 1500 psig, and 0.4 ml/min injection rate by alternative injection of N(2)and CO(2)in succession designed to suit the application based on optimum operating conditions. The results show that both CO(2)storage capacity and CH(4)recovery improved significantly when gas alternating gas (GAG) injection was considered. The best results were observed at lower N(2)cushion volumes (1 and 2 PV). Therefore, the GAG injection method with N(2)as cushion gas can potentially increase both CO(2)storage and CH(4)recovery of the gas reservoir. This technique if employed will assert the current position and provide vital information for further researches aimed at promoting environmental sustainability and economic viability of the EGR and CO(2)sequestration processes.