Reactivating Oil Producer and Water Injector Wells Using Single Phase Retarded Acid and Fiber Optic Equipped Coiled Tubing

Abstract This technical article outlines the implementation of single-phase retarded acid (SPRA) and its advantages over double-phase retarded acid systems. It follows an established Matrix Stimulation Engineering (MSE) workflow, leading to improved hydrocarbon production in an oil producer well and enhanced water injection in an injector well within the operator's field. Previous stimulation techniques, employing a constant volume/feet dosage of hydrochloric acid via conventional coiled tubing (CT) in 6-inch open-hole horizontal wells targeting tight-carbonate formations, yielded inconsistent results and rapid declines in hydrocarbon production rates or water injection rates. In response, an MSE workflow was introduced in 2019 (Abdelrehim et al, 2020), incorporating fiber-optic-equipped CT and high-pressure jetting guns. Now, with the adoption of SPRA, the process is further optimized, leveraging slow acid reaction to enhance worm holing. The understanding of formation damage plays a crucial role in designing appropriate matrix stimulation fluids. Pre-flush fluid system was designed and pumped prior main treatment for wellbore conditioning. To address damage bypass in tight carbonate formations, a novel single-phase retarded acid technology with a slow reaction rate was employed for deeper penetration. Utilizing fiber optic cable as a temperature surveying logging device during injectivity tests allowed for the assessment of fluid distribution along the horizontal openhole section. This data, juxtaposed with petrophysical data and post-treatment production logs, empowered the engineering team to fine-tune chemical pumping schedules. Implementing SPRA through the established MSE workflow facilitated selective fluid placement in target producing zones, leading to deeper penetration and enhanced wormholes. Consequently, there was a notable improvement in hydrocarbon production from producer well and increased water injectivity in injector well. This article highlights the utilization of SPRA within a MSE framework, incorporating distributed temperature surveying (DTS) for assessment. It demonstrates SPRA's efficacy in enhancing hydrocarbon production and water injection in the operator's field. The use of the SPRA has a positive environmental impact by reducing carbon emissions as a result of less volume, consequently utilizing less logistic and well operation time compared to regular acid or double-phase retarder acid systems.