Conceptual Selection of Disposal Alternative for Low-Carbon Water Handling Systems

Abstract As part of the ongoing efforts to minimise energy consumption and reduce GHG emissions, PDO has set a new target of eliminating Deep Water Disposal (DWD) practices by 2030, which typically utilise high energy pumps to inject produced water into underground reservoirs without EOR benefit at depths greater than 800 m. This paper aims to identify and assess different water handling alternatives and compare them against DWD for three Gas Assets: S, K and R. The study comprises the following value drivers: Lower GHG Emissions, Maximize PR Reuse, Minimize LCC, Minimize Deferment Risks, and eliminate DWD. Assured water forecasts were generated from annual business plan activities and converted to water balance figures against the associated sink destinations. Water from each station was analysed for Cation/Anion Analysis, ICP Analysis, OIW Analysis, and NORM analysis. Additionally, power for operating the existing water systems was quantified and projected in tons of CO2e. The alternatives identified for assessment are Algae Treatment, Aquifer Recharge, Agricultural Reuse, Water Injection, Wetland treatment, Evaporation Ponds, and Industrial Salt Production. The requirements for each alternative were recorded. The high intensity disposal pumps used in the targeted facilities were estimated to contribute to 0.34% of the overall gas assets power demand. The rest of the PW is relocated to neighbouring oil assets to use in water injection for EOR. The quality of water in K and S was found to be very high in salinity and contaminated with NORM by more than double the allowable corporate limit. Whereas R was low in salinity with low NORM (it is processed DM water, and the field is dry). These qualities were compared against the requirements of the alternatives. Upon a high-level screening, the remaining feasible options were evaporation ponds for all facilities and wetlands for R. Further technical and economic analysis was done on the feasible options, and Unit Treatment Costs (UTC) were calculated. K and S were recommended to continue with water disposal, while R was taken forward for wetland options. This paper provides a useful conceptual methodology for selecting the most suitable alternatives to traditional produced water disposal systems. It provides several options along with their minimum requirements, equipment, pros and cons. Ultimately, this will encourage other operators to consider water management and select low carbon and sustainable solutions.