Effects of pressure build-up and CO2 migration on brine production

• Published in: Geosciences journal (Seoul, Korea) Vol. 24; no. 4; pp. 425 - 440
• Main Authors: Han, Ahreum, Kim, Taehee
• Format: Journal Article
• Language: English
• Published: Seoul The Geological Society of Korea 01.08.2020; Springer Nature B.V; 한국지질과학협의회
• Subjects: Brines; Carbon dioxide; Distance; Earth and Environmental Science; Earth Sciences; Injection; Injection wells; Intervals; Length; Optimization; Overpressure; Pressure; Pressure effects; Saline water; 지질학; storage efficiency; maximum injection pressure; extraction well; extraction interval
• ISSN: 1226-4806; 1598-7477
• DOI: 10.1007/s12303-020-0012-0

The need to reduce the maximum injection pressure has been considered an important subject for storage efficiency and safety. Brine extraction from the storage formation is one of the most reliable methods to manage formation pressure. When brine extraction is performed, it is very important to select the optimum location of the extraction well, where the storage efficiency can be maximized. In this study, the sensitivities of the distance between injection/extraction wells and the length or depth of extraction intervals was investigated with a 20,183 metric ton/year injection/extraction rate for 30 years. The injected CO 2 moves upward by buoyancy and spreads horizontally along with the top of the storage formation. Therefore, CO 2 was re-extracted through extraction wells in the case with fully perforated intervals. Even if the intervals were shorter than 20 m, CO 2 was re-extracted with an extraction distance within 500 m from the injection well. Excluding scenarios with CO 2 re-extraction, the injection pressures at injection wells were reduced by 71.7% and the volumes of CO 2 plume increased by 18.8%, compared with the maximum pressure and the gaseous volume of CO 2 in case 1. It was found that the shorter extraction interval of the well located in the bottom part of the reservoir can significantly improve the injection performance, thus reducing the chance of CO 2 re-extraction. With the viewpoint of long-term injectivity, in general, it was confirmed that as the distance of brine extraction increases, the injectivity decreases. However, we could find a considerable exception in general trends. If the extraction well is located within the lateral extension range of the CO 2 migration, brine extraction can limit the lateral migration of CO 2 and consequently increase the overpressure induced by the injection. Therefore, when determining the optimal location of the extraction well, the expected migration range of CO 2 as well as the distance to the injection well, the depth and length of the extraction interval should be considered.