Major Greehouse Gas Reduction from Flare Verification

Abstract Membranes are utilized in Acid Gas Removal System (AGRS) at offshore platform to remove carbon dioxide (CO2) from sour gas reservoirs. CO2 selectively permeates the membrane compared to methane and the CO2 rich stream is sent to flare system as permeate flare. This permeate flare is measured by an Ultrasonic Flowmeter (USM) installed as permeate flare meter in 2020. When verification exercises was done, it was first observed that there was a huge discrepancy in mass balance values with the mass output being significantly higher than mass input by 10 to 20%. Upon verification of the inputs from permeate flare meter to Distributed Control System (DCS), it was initially hypothesized that standard density input assumptions of 0.714kg/Sm3 is unrepresentative of the density values of the supposedly CO2 rich permeate flare. This has caused a large overestimation of permeate flare values. Operations crew at offshore platform utilized CO2 sampling tubes as a solution for quick sampling of permeate flare and sampling results yielded CO2 compositions of 40 mol% which was the maximum limit of the tubes. Using a conservative approach of assuming the remaining composition of permeate flare to be methane, the permeate flare standard density was then estimated to be at 1.156kg/Sm3. Applying these setting to the input at DCS then yielded an initial 39% decrease to permeate flare values. Meanwhile, third party analysis of permeate flare compositions are conducted on a later date with density values from permeate flare compositional analysis and differing. The team studied further into the capabilities of the permeate flare meter on live density calculation and proceed to set up trending for calculated density from the meter. The density values calculated by the permeate flare meter were comparable to sampling results. Furthermore, the mass balance between input and output has significantly been improved to be within 3% to 5% of each other. As a result, the team has successfully achieved reduction in reported permeate figure by 4.81 mmscf/d annualized or 97034.26 tCO2e.