Selection of Optimized Gas Processing and Sulphur Recovery Technology Line Ups for Different Feed Gases

Abstract

Abstract Petroleum Development Oman (PDO) is developing sour gas fields across the country in order to meet the gas demand to sustain industrial growth in Sultanate of Oman. The projects involve development of high pressure, high temperature sour associated gas reservoirs with oil rims as well as non-associated gas reservoirs. The reservoirs are located at a depth of around 3 - 5 km. The sour gas produced contain significant amounts of H2S and CO2 in addition to other contaminants such as mercaptans, carbonyl sulphide (COS) and carbon disulphide (CS2). For a couple of projects, in the absence of a suitable sink for the acid gas and due to HSE risks associated with high pressure acid gas injection (> 400 bar), sulphur recovery has been selected as the acid gas processing route. The various sour gas fields being developed have different levels of contaminants whereby employing a standardized process line up of gas treatment and sulphur recovery technologies may not be either technically feasible or economically optimum. Among the many engineering challenges associated with any sour gas field development, the combination of Sultanate of Oman's ultra-high sulphur-recovery efficiency (SRE) specification of 99.9%, and the very stringent SO2 emission specification of 35 mg/Nm3, poses a steep challenge and pushes established technological boundaries. Further, if the sweet gas produced will have to be exported to the Government Gas network, it has to meet a tight total sulphur specification of < 5 ppmv. In case the gas is to be used for internal consumption within PDO, the total sulphur specification is < 100 ppmv. The combination of these regulatory requirements makes the design of the gas treatment and sulphur recovery facilities extremely challenging. It is clear that best-in-class solutions would be necessary for the projects to comply with the standards. The concentration of different contaminants in the feed gas and the selection of the sweet gas export route dictate the choice of optimum gas processing and sulphur recovery technologies and their integration. For the projects under consideration, PDO has evaluated a wide portfolio of gas processing and sulphur recovery technologies and has selected process line ups comprising of a fit for purpose combination of technologies. An integrated approach ensured that interfaces between the different units were efficiently managed and the configuration was fully optimized thereby enhancing energy efficiency. This paper presents the selection of the optimized combination of gas processing and sulphur recovery technologies that cater for different feed gas contaminant concentrations and yet comply with the regulatory requirements.