Sustainable Water Sourcing and Treatment Methods for Water Injection Projects Using Shallow Aquifer: Pre- and Post-Implementation Evaluation

Abstract

Summary Reservoir supporting by water injection is a mandatory aspect in managing aged and depleted fields; however, securing a sustainable water source with low treatment expenditures and fewer operational problems is still a challenge for operator companies. Gulf of Suez Petroleum Company (GUPCO) implemented water injection using seawater, aquifer water, and a combination of both to support the depleted reservoir blocks in an offshore field. GUPCO has been producing the shallow water aquifer for 27 years, securing the field’s water injection needs until the field cumulative production surpassed one billion barrels of oil. Before field implementation, the company and its joint venture performed several compatibility tests, field studies, and scale tendency calculations to confirm the benefit of using the aquifer water over Gulf of Suez (GOS) seawater. Indeed, the aquifer formation water has less tendency to form sulfate hard scales due to its low content of sulfate ions compared with seawater. The key advantage of the groundwater aquifer is that there is no need to use a water injection pipeline from the onshore facility to the offshore field platforms. The application of seawater injection had already been implemented as a stage in the field development phases. Seawater injection dedicated higher costs and additional operational challenges to meet the required injection water quality standards. However, the aquifer water is being extracted and produced via offshore production wells to support the producing field. These offshore water source wells (WSWs) were completed with electric submersible pumps (ESPs) to ensure sufficient water supply and with sand screens and gravel pack completions for sand control and solids filtration. Field studies reached the conclusion that WSW output water may not receive any surface treatment or additional filtration, and it can be directly distributed to injector wells through surface pipelines. Furthermore, two dumpflooding wells were completed to support the main producing reservoirs, using the aquifer water in addition to the already-implemented system. However, the aquifer water contains dissolved carbon dioxide (CO2); therefore, the deposition of carbonate scales was predicted in the study phase and confirmed in the operation phase. Generally, this aquifer water can be generalized and used as a good alternative to seawater for water injection projects in the GOS area. This paper will address the successful application of GUPCO for this unique water injection system and the encountered challenges and drawbacks to achieve maximum field efficiency. The paper will also compare the actual case studies and field applications of implementing seawater and aquifer water in water injection projects. The comparison will include reservoir souring, scale deposition, operational efficiency, and implementation challenges. Additionally, the paper will discuss an additional project using independent satellite seawater treating and injection system in the subject field for knowledge sharing and comparison purposes.