When developing marginal fields, the maximisation of production and the minimisation of cost are two key drivers. This paper is concerned with one of the main cost streams in terms of capex, opex, environmental threat and management time; the treatment and disposal of produced water. Whilst many of the concepts are applicable to any marginal field development, the thrust of the paper is aimed at the Niger Delta's particular situation.
To effectively design water treatment and injection systems, a wide range of skills is needed. If water is required for pressure maintenance or sweep, the decision must be taken whether to use produced, aquifer, sea or commingled water. The water needs to be accurately characterised (a difficult task in itself). The potential for scale formation and souring must be assessed. The geology of the injection zone should be understood and its injectivity measured. The best techno-economic treatment and injection system needs to be designed; this should be robust and well-proven for use in local conditions.
Worldwide, there is a shortage of ‘available’ oilfield water management expertise. It is therefore unrealistic to expect fledgling oil companies to have such expertise in-house. If each oil company in the Delta Region ‘goes it alone’ the repercussions will include: a) fewer available experts; b) greater capital expenditure and environmental damage across the region due to ‘sparing’, construction and drilling; c) lack of water trading; d) less ability to provide community services of substance; e) greater risk of environmental incidents, and; f) increased regional opex.
This paper describes the rationale for a small number of centralised water processing systems: each taking water from several oil companies; disposing or re-supplying it responsibly and providing in-depth assistance to the local communities; with expected savings in project studies, implementation time, capex, opex, environmental clean-up and water resources.