_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 225131, “From Emissions to Revenue: Emissions Reduction and Hydrocarbon Recovery From Permeate Through Acid-Gas-Removal Unit Optimization and Synergizing of Upstream and Downstream Processes, ” by Ariff S. Ismail, Elmi B. Ismail, and Haslina Abdullah, SPE, Petronas, et al. The paper has not been peer-reviewed. _ This paper describes the operator’s zero-cost solutions to reduce greenhouse gas (GHG) emissions by 30% from the total permeate stream, power generation, and purchased electricity; and to add more than 20 million of revenue annually through monetization of recovered hydrocarbon from permeate streams in the acid-gas-removal unit (AGRU) at one of its natural gas terminals in Malaysia. Introduction Offshore upstream natural-gas suppliers transport their production to multiple onshore receiving terminals, where it is treated and blended to meet required specifications, particularly the maximum CO2 mol% at the gas-processing-plant (GPP) delivery point. In one of the natural-gas supply chains, where the CO2 concentration exceeds GPP requirements, the gas is processed at a terminal equipped with a membrane-based AGRU system, which is designed to reduce CO2 concentration in sales gas. AGRU Design Feed gas from offshore upstream suppliers is first directed to the pretreatment unit. The AGRU is equipped for two stages of gas processing with its primary and secondary membranes. The treated, on-spec gas leaving the primary membrane is compressed by the sales-gas compressor (SGC) before being exported to the GPP. The byproduct stream from the primary membrane, known as the permeate, which still contains a high concentration of valuable hydrocarbons, is then sent to the secondary membrane by a booster-gas compressor (BGC) for further hydrocarbon recovery (Fig. 1). The recovered hydrocarbons from the secondary membrane are routed back to the primary membrane by a regeneration compressor; in the primary membrane, they are commingled with the on-spec gas upstream of the SGC and metering stations. The permeate from the secondary membrane, rich in CO2, is directed to a thermal oxidizer (TO) to destroy the remaining hydrocarbon residue in the stream. Any deviation in operating conditions from the AGRU design, such as feed-gas flow rate or composition, can cause inefficiencies, leading to higher permeate flow and significant hydrocarbon loss. The terminal with the AGRU is currently receiving 25% less feed gas than its design capacity, along with a 5-mol% reduction in CO2 content. These deviations have altered the membrane’s selective permeation, affecting the efficiency of the AGRU. The permeate CO2 contains significant amounts of hydrocarbon, emitting approximately 0. 8 MMtCO2e and resulting in the loss of 10 MMscf/D of sales gas. Meanwhile, the gas-compression system consumes 7 MMscf/D of the fuel gas, emitting approximately 0. 15 MMtCO2e. A collaborative team comprising upstream and downstream personnel and Malaysian regulators was formed with the primary focus of reducing GHG emissions from the terminal’s AGRU while recovering hydrocarbons from the permeate to be monetized as sales gas at the GPP. The operator first conducted a thorough situational assessment and baseline analysis of the AGRU-membrane-design parameters, comparing them with current operating conditions.
Chris Carpenter (Wed,) studied this question.