Effective Treatment and Handling of Produced Water

Abstract

Editor’s Note: The oil and gas industry is under public scrutiny like never before on a host of health, safety, and environmental issues. These concerns are already affecting how companies operate and interact with the public. This series is intended to shed light on how the industry is actively confronting these challenges or how it should address them going forward. Produced water is an inevitable by-product of oil and gas production. It is estimated that for every barrel of oil produced worldwide there are roughly four to five barrels of water co-produced. As it contains a wide range of contaminants, the discharge of produced water could potentially cause harm to the environment, and therefore should be monitored closely. For the offshore oil and gas industry, approximately 75% of the produced water is treated and then discharged into the ocean, with the rest being reinjected. While onshore, roughly 90% of this water is reinjected, with the rest being treated and reused or discharged. With the rapid development of shale oil and gas, and the demand for water for hydraulic fracturing, there is an increasing emphasis on flowback and produced water reuse. The measurement of oil in produced water is vitally important, for both regulatory compliance monitoring and data collection for the development of future government regulations and operators’ corporate environmental policy. Of course, to calculate the total amount of oil that is discharged via produced water, the volume of that water must also be measured accurately. Measurement of the oil in produced water is also important for the control of the water treatment process itself. Management of produced water varies with operators, geographical locations, and field history. Good produced water management practice should involve different disciplines, including reservoir engineers, production engineers, production chemists, and environmental engineers. It would also require an integrated approach, taking into consideration the different options, as well as production history and profile. Often water production becomes a limiting factor for continuing oil production economically for a specific field. How to best manage produced water in oil and gas production will therefore have a significant impact economically, socially, and environmentally. The key to produced water management is to prevent water getting into the wellbore, and to minimize the water being brought to the surface. Failing this, produced water must then be treated, reinjected, and/or discharged or reused. Using Online Oil-in-Water Monitors The use of online oil-in-water monitors can play an important role in the management of produced water. There are many benefits in using online continuous oil-in-water monitors, but particularly as they provide continuous information on a minute-by-minute basis, if not more frequently. Thus, not only can one spot process upset conditions quickly and take actions to rectify the situation, but such monitors can also be used for process optimization, such as chemical dosing.