Well water treatment

Mature oil fields are a reality that producers world over have to wake-up to every morning. Newer technologies, scientific methods and new areas of study may all facilitate oil recovery from ageing wells, but never reverse the ageing process.

One of the major problems a mature field throws up is produced water. At 98% of the total waste generated, produced water stands as the largest waste on an oil and gas field. The Produced Water Society, formed in the US, recently made a presentation in Oman aimed at understanding the problem the gulf state faces owing to its large percentage of mature assets. A conference in Muscat discussed various cost-effective methods for handling the waste, which is not only useless, but also toxic.

According to the Produced Water Society, the treatment of produced water is a major component of the overheads involved in producing oil and gas. Wells may start out producing little water, but sooner or later all oil wells produce a much larger volume of water than oil. The ability to efficiently and economically dispose of this water is critical to success in the oil production business.

A mixture of performance standards for disposal processes and regulations limiting discharges mandates the standards for treatment of produced water. Produced water can be used as a source of water for waterfloods or pressure maintenance projects. If reuse is not an option, produced water is disposed of by discharge into the sea or injection under ground.

Standards of treatment for reuse are set by industry technical organisations, such as the American Petroleum Institute (API) and its member companies, the Oil Producers Association (OPA) and other industry groups. Standards for produced-water disposal are determined by state, national and international regulatory bodies.

One of the widely accepted definitions of produced water is the brine brought up from the hydrocarbon bearing formation strata during the extraction of oil and gas, and can include formation water, injection water, and any chemicals added downhole or during the oil/water separation process.

According to industry insiders, produced water in places like Oman has reached up to 80% of the fluid extracted. The disposal of this water is becoming a mammoth task, as in the Middle East the water has to be disposed onshore, unlike the North Sea, where it is disposed of into the sea/ocean after treatment.

Onshore disposal of produced water is a lot tougher, as regulations are more stringent. The disposal is also energy intensive. The water has to be pumped back into the ground after it has been processed until it contains only five parts per million (ppm) of oil.

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