Alternating N2 and CO2 injection as prospective technique for delaying CO2 breakthrough during enhanced gas recovery in consolidated rocks

Mohammed, NUHU; Abubakar, AJ; Enyi, GC

Abstract

The use of carbon dioxide (CO2) for simultaneous methane recovery and CO2 storage is gaining recognition globally within the oil and gas industries. On the other hand, most of the residual natural gas recovered during the EGR process is highly contaminated with the injected CO2 due to their nascent miscibility nature, resulting in premature breakthrough. In this study, N2 gas was used as a buster to mitigate such early mixing between the CH4 and CO2. The experiment was administered at reservoir conditions of 40oC temperature, 1500 psig of pressure, the optimum injection rate of 0.4ml/min, and at varying N2 cushion volumes (8-36 cm3) using Bandera gray as the porous medium. Further experimental tests were administered to study the effect of this technique on connate water salinity with 5-20% water salinity been considered. The increase in buster gas volume was in direct proportion to delayed CO2 breakthrough, with the maximum at 36cm3 buster volume. This breakthrough occurred at 177 minutes which is 110min additional delayed than the conventional CO2 flooding with a breakthrough time of 67 minutes. This was due to the high shielding barrier inhibited by nitrogen, making it difficult for the CO2 to dispersed itself and mixed with the nascent natural gas resulting in delayed breakthrough as it plumes transverses into the CH4 during the displacement process. Furthermore, a poor performance was observed with the inclusion of the connate water salinity, especially at 20% wt. This was because the free pore spaces were already occupied by connate water molecules prior to the cushion gas injection which hinders its economic potential application. Copyright 2020, Society of Petroleum Engineers.

Citation

Mohammed, N., Abubakar, A., & Enyi, G. Alternating N2 and CO2 injection as prospective technique for delaying CO2 breakthrough during enhanced gas recovery in consolidated rocks. Presented at Abu Dhabi International Petroleum Exhibition & Conference (ADIPEC), Virtual

• Presentation Conference Type: Other
• Conference Name: Abu Dhabi International Petroleum Exhibition & Conference (ADIPEC)
• Conference Location: Virtual
• End Date: Nov 12, 2020
• Publication Date: Nov 12, 2020
• Deposit Date: Nov 12, 2020
• Book Title: The Abu Dhabi International Petroleum Exhibition & Conference (20ADIP)
• ISBN: 9781613997345
• DOI: https://doi.org/10.2118/202716-MS
• Publisher URL: https://doi.org/10.2118/202716-MS
• Related Public URLs: https://www.onepetro.org/; https://www.adipec.com/
• Additional Information: Event Type : Conference