Treatment of water disposal injection process by oilfield chemicals: Maintaining injectivity and environmental effects

Oil production from hydrocarbon reservoirs is invariably accompanied by water production, which poses significant challenges to both production and injection systems, particularly due to the formation of mineral scales. While scale formation in production wells has been extensively studied, its impact on water disposal wells which is critical for managing produced water and ensuring environmental compliance, remains underexplored. This research gap is especially important because disposal wells face unique challenges, such as injectivity loss, environmental risks from wastewater release, and the need for sustainable scale management practices. This study addresses these challenges by investigating mineral scale formation in a water disposal well in southern Iran. Unlike previous research focused on production wells, this work emphasizes the unique operational and environmental implications of scale precipitation in disposal wells. For this purpose, field information including well schematic, disposal injection system data and acidizing jobs processes performed in well A is investigated. Analyzing and simulation of the composition of the water disposal sample resulted that maximum amount of scale precipitation in surface pipeline is equal to 92 mg/l owing to CaSO 4 precipitation. Also, CaSO 4 and CaCO 3 are precipitated within near wellbore area. CaSO 4 is the dominate scale type and maximum amount of this scale is 656 mg/l and CaCO 3 is minor scale type with 54.42 mg/l in near wellbore condition. Furthermore, based on the injection pressure and injection rate data assessment in the time interval between two consecutive acidizing jobs, the formation of scales and the reduction of injectivity in well A are proved. Also, from operation point of view and according to ASTM-0374 method, scale inhibitor should be injected continuously at a concentration of 40 ppm from the surface to cover the entire injection system. The results show that scale inhibitor is an effective solution in prevention of scale precipitation, with 95.2% efficiency in scale formation inhibition. By focusing on disposal wells, this study provides novel insights into scale management strategies tailored to the unique requirements of water disposal operations. The findings highlight the effectiveness of chemical inhibitors in preventing scale formation and offer a sustainable alternative to conventional acidizing methods. This research contributes to advancing environmentally responsible practices in oilfield water disposal, addressing a critical gap in the field.