Abstract
The Mukhaizna heavy oil field in Oman is one of the world's largest steamflood operations. With more than 3,000 wells drilled (producers and injectors), gross fluid production has surpassed 900K bbl/day, with steam injection of 600K bbl/day and water disposal of 300K bbl/day after 17 years of successful steamflooding.
These large volumes of produced fluids undergo various treatment processes to prepare them for either sale, boiler feedwater for steam generation, or disposal. With water cuts exceeding 90% and fluid chemistry changing with new fluid streams added from exploration areas, technical difficulties compelled a multidisciplinary team to share operational intelligence to optimize the processes of dehydration, de-oiling, water treatment, and disposal.
To address the challenges posed by the substantial volumes and high temperatures of viscous produced fluids, free water knockout vessels, skim & dehydration tanks, and induced gas flotation are used, enhanced by a carefully optimized selection of chemicals, resulting in a reasonably efficient dehydration and de-oiling processes.
The water treatment plant (WTP) uses a sophisticated treatment process to comply with the specifications for boiler feedwater. This process involves chemical precipitation softening methods, ion exchange with strong acid cation (SAC), a reverse osmosis membrane, and thermal desalination using one of the world's largest Mechanical Vapor Compressors (MVC).
The high volumes of multiple disposal fluids demand a complex and ecological disposal system. The current process includes conventional deep subsurface disposal and segregated evaporation ponds. Other environmentally friendly solutions are being considered, including autonomous inflow control devices/valves and the use of reed beds for wastewater treatment.
. Due to the operation's size and complexity, the team examined leveraging modification of the facility to improve produced flu id cost and to recycle selective waste streams. This approach would alleviate bottlenecks, resume production of shut-in high-water-cut wells, optimize chemical expenditures, and enhance the water quality entering the WTP's SAC inlet.
The team has recommended both mechanical and chemical solutions to unlock the full potential of these mature assets, leading to savings of more than 20% on some chemicals and a big gain in production from re-opening the shut-in wells.
