Integrated Scale Removal and Production Recovery Lessons from United Arab Emirates

Abstract

Scale deposition in oil and gas production systems occurs when changes in pressure, temperature, or fluid composition disturb the chemical equilibrium of produced waters, causing sparingly soluble inorganic salts to precipitate and adhere to tubulars, wellbores, and surface facilities. As reservoir fluids flow from high-pressure, high-temperature conditions to lower-pressure environments, dissolved ions such as calcium, barium, and strontium can exceed their solubility limits, leading to the formation of sulphate or carbonate scales through processes such as mixing of incompatible waters (e.g., formation water and injected seawater), flashing of CO2, or water evaporation. These mineral deposits progressively harden and bond to metal surfaces, restricting flow area, increasing pressure drop, impairing downhole and topside equipment, and ultimately causing significant production losses if not effectively managed. This paper presents an integrated scale remediation and production recovery campaign conducted on wells in the Upper Zakum field experiencing significant production decline due to severe Strontium Sulphate (SrSO4) scale deposition compounded by Naturally Occurring Radioactive Material (NORM). Production in candidate wells had declined by over 50%, with conventional intervention methods proving ineffective due to the hardness of the scale and the operational constraints associated with radioactive contamination. The objective of this study is to demonstrate the effectiveness of a tailored intervention strategy combining advanced chemical treatment, optimized mechanical milling, and a structured NORM handling protocol to safely and efficiently restore well productivity. The approach integrates laboratory-driven fluid selection, engineered bottomhole assembly (BHA) design, and real-time operational adjustments to enhance scale removal performance while ensuring compliance with strict health, safety, and environmental (HSE) requirements. The implemented workflow delivered significant improvements in operational efficiency and production performance. Rates of penetration (ROP) during milling increased substantially following the introduction of chelating agents, and overall intervention time was reduced compared to previous campaigns. Production restoration exceeded expectations in both case study wells, confirming the effectiveness of the integrated approach.