Gas fields containing contaminants continue to not only challenge new field development projects, but also existing operations worldwide. Unforeseen variables such as increasing levels of contaminants from existing fields paired with increased sales gas demands, justifies the urgent need of identifying limits and pushing boundaries of existing facilities to handle the operation parameter changes.

This study focuses on a debottlenecking study done for an existing operational facilities located at the Caspian Sea area, with an original inlet H2S design of 45 ppmv, to be processed down to < 3.5 ppmv. New sales gas demand requires for the existing facilities to process sour gas from reservoir having a maximum level of 580 ppmv H2S, at a higher continuous sales gas volume. Challenges to achieving this also includes uncertainties due to fluctuations of H2S levels from the reservoirs, with some variations going from <10 ppmv to 300 ppmv H2S coming out from the same well.

Discussion will elaborate on challenges in meeting the new sales volume with expected increased in H2S levels from existing wells, and how limitations of existing facilities (Acid Gas Removal Unit, Acid Gas Incinerators and materials sour service compatibility) are addressed to produce a feasible operating envelope, with minimal changes to existing operating facilities.

Actual operating data from approximately 5 years of operation was analyzed to determine the feasibility of the AGRU and Incinerator to handle higher H2S levels in feed. This is in anticipation of continuous feed gas volume of 500 MMscfd, at blended H2S levels of between 45 ppm to 162 ppm (worst case scenario). Existing facilities sour materials compatibility analysis are also done to determine the feasibility of the operating envelope.

In the analysis, data from actual operating history and new production profiles are plotted against a feasible operating curve developed for the AGRU. The resultant graph gives an indication of the existing AGRU capability to manage incoming increase in gas volume and H2S levels. The analysis also evaluates the impact to the Incinerators, with new emission dispersion simulations done, to ensure operating curve complies with local environmental regulations on emission dispersion.

The analyses conclude that the existing facilities is deemed adequate to handle new gas demand, with some curtailment on blended H2S levels to ensure only minimum changes and upgrades are required to existing facilities. The curves developed are hereby used as a reference for operations of the facilities in the future, whilst the methods applied here can be used as a reference for future sour facilities debottlenecking.

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