Well Integrity Protection Using Corrosion Inhibitor Treatment System for Sour Gas Producers in Bahrain Field

Abstract

Gas wells of the Bahrain Field in the Kingdom of Bahrain suffer from corrosion and scale issues due to the presence of water, Carbondioxide (CO2), and a high Hydrogen Sulphide (H2S) content in the formation. The current method applied to overcome these issues involves bullheading a corrosion inhibitor batch treatment. However, high costs and low effectiveness are driving a shift from batch treatments to continuous downhole treatment techniques. This paper describes the process of converting to continuous downhole treatments. The process of continuously injecting a corrosion inhibitor downhole is much more efficient and cost effective than bullheading the well with a corrosion inhibitor. This application reduces the potential of scale buildup and avoids well deliverability reduction problems. Additionally, the injection system may be used to continuously inject multi-blend chemicals downhole and can thereby treat other problems downstream and reduce the need for surface inhibition. Designing the system with the appropriate chemicals and tubing material is the key to success. The selection of materials and chemicals should take into account the CO2, H2S, temperature, and pH concentration in the candidate well. The chemical injection string can be installed into a live well using a capillary unit, without the need to shut-in or choke-back production. This can be carried out as a rigless installation similar to a coiled-tubing operation, but on a much smaller scale. The capillary unit is small and compact, and is mounted onto a truck or a trailer. The unit can be mobilized and de-mobilized for operation rapidly and easily, saving time and cost. Routine maintenance to the injection system is crucial for a long-term successful application. The qualification of the chemicals should be stringent and must allow for friction loss through such small inner diameters (IDs), however it must also withstand the pressures, temperatures, fluids, and extreme downhole conditions that it will face. Using the continuous downhole injection system will positively impact well integrity, improve completion lifetime, assure production continuity, reduce downtime and treatment operating costs, and avoid coiled-tubing descaling operational costs. Installing a downhole treatment system can also be used for other purposes if needed, such as H2S management, deliquification, scale inhibition, controlling paraffin/asphaltene, and treating downhole pumps.