Innovative H2S Management in Sour Wells: Safe Rigless Approach

Abstract This study explores the application of a completion design solution which enables downhole sweet gas injection via an insert string tailored for high hydrogen sulfide (H2S) wells, aimed at managing H2S concentrations within the wellbore through downhole dilution with an external sweet gas source. This approach enables the controlled reduction of H2S levels directly through the production path through the wellbore to the surface, allowing hydrocarbon production with acceptable H2S concentrations. This approach reduces the need for extensive surface processing and enhances the profitability and operational viability of high-H2S wells. This abstract presents an innovative, yet simple completion design that enables sweet gas to be injected into the wellbore with minimum required surface injection pressure to get mixed downhole with sour gas to reduce H2S content by dilution. The system employs advanced downhole engineering to achieve targeted gas injection within high-H2S wells, allowing precise control of injection depths without the need for rig-based intervention. The installation begins with rigorous well preparation, along with integrity checks, after which an intermediate spool assembly is installed just below the wellhead and secured by a shallow bridge plug. This provides a structurally stable base and pressure isolation for the subsequent insert string or coiled tubing installation. The insert or coiled tubing string, specially equipped with a precision injection valve, is run downhole to achieve accurate gas placement at the designated shallow injection depth. This configuration facilitates uninterrupted downhole gas injection, ensuring controlled H2S dilution with optimized injection precision to stabilize production flow while maintaining well pressure. The proposed system demonstrated substantial improvements in H2S management, economic performance, and operational sustainability. By introducing an external sweet gas source directly into the production stream, the system effectively diluted downhole H2S concentrations to manageable levels, thus leading to a reduction in the H2S level in the well-stream. The system also minimizes the need for surface-level treatment yielding reduced downstream processing costs. This method led to significant operational savings by maintaining well pressure stability and achieving efficient fluid lifting without additional mechanical interventions. Moreover, the possible rigless design facilitated faster well restarts following shutdowns, reducing downtime and supporting stable production. In terms of business value, this system will reduce operational costs and production risks in high-H2S wells. By mitigating surface H2S processing, the approach simplifies facility requirements, minimizes environmental and safety risks associated with handling high-H2S flows, and translates to lower equipment and maintenance expenditures related to the subsurface. The field data supports the conclusion that subsurface dilution enables safe well operations, by reducing the rupture exposure radius (RER). This deleted section is not necessary. This technology will help to unlock the sour gas potential at reduced costs. The rigless and remotely operated system allows wells to be quickly restarted, enhancing production continuity, reducing non-productive time (NPT), and extending well lifespan. The flexibility of the system also permits dynamic responses to fluctuating H2S levels without costly interventions, securing long-term cost savings and increased profitability. The rigless downhole gas sweetening using insert string e.g. inverse gas lift system presents a breakthrough in high-H2S well management by using precision downhole gas dilution to optimize production and reduce processing costs. Its rigless, versatile design promotes sustainable H2S management, enhances well productivity, and extends operational efficiency without requiring rig-based intervention. This adaptable, proactive approach to H2S management supports industry sustainability goals by offering a low-impact, optimized solution for managing high-H2S reservoirs.