This paper describes the development of the Production Water Management Plan for Petroleum Development Oman (PDO) and its subsequent implementation. It outlines the current water production and disposal practices, the existing Omani legislation on waste water disposal, and trials carried out by PDO, all of which resulted in the development of the plan and an implementation strategy agreed by PDO and the Government to achieve a produced water management operation that is sound both in environmental principle and practice.
PDO currently produces some 330,000 m3/day of water as a by-product of its oil output of about 135,000 m3/day. The volume of this production water has been steadily increasing over time and is predicted to rise to about 650,000 m3/day by the year 2005.
The disposal of large volumes of production water presents PDO with important environmental and economical challenges. In order to manage these challenges, the PDO Production Water Management Plan was developed and agreed with the Government and private shareholders.
In resolving the best technical solution for disposal at any of PDO's production sites, PDO has fully evaluated the principles of the PDO Production Water Management Plan by testing and then implementing the latest state-of-the-art technologies. Studies and trials have been carried out in order to achieve improved cleanliness of production water, and to identify economically attractive usage alternatives for the water. In particular field trials to test various deoiling equipment have been carried out, as well as a detailed study and field trial into the use of disposal water as irrigation water for an agricultural project. As a pre-study for the agricultural conceptual work, other alternative water disposal methods, such as the use of evaporation ponds, ocean discharge and production of potable water, were evaluated but found to be economically less attractive than the agricultural alternative.
Having completed these trials and studies, plans have been put in place to bring production water disposal in all production centres into line with the principles of the Production Water Management Plan. The main outcome has been the implementation of Deep Water Disposal for most production centres in the South of Oman.
The disposal of large volumes of production water presents PDO with an environmental and water resources conservation issue of considerable importance, in terms of both quality and overall quantity. The volume to dispose of is expected to rise over the next decade, with no significant increase in the volume of water that can be profitably utilised either for reservoir pressure maintenance or for other purposes.
High water production is caused by bottom or edge water drive, high oil viscosity and low density contrast. Well over half of PDO's Oil initially in Place (STOIIP) is in reservoirs with conditions resulting in high water production due to natural water drive.