Towards Low-Cost Zero Liquid Discharge in Offshore Production Operations

Produced water from oil and gas operations across the globe is steadily rising towards a 3:1 ratio of oil production, if not managed properly leads to pollution and severe environmental impact. Treatment and disposal costs remain the primary concern with the ongoing global push towards the transition to cleaner energy and Zero Liquid Discharge (ZLD). Typical PWRI specifications required are Oil-In-Water (OIW) less than 5-10ppm, total suspended solids less than 10ppm, particle size typically less than 2μm for other contaminants and chemicals. These physical and chemical properties depend on the geographic location of the field and reservoir formations, resulting in high treatment costs and complex operations. A new PWRI technology which focuses on reducing the oil droplets' size was studied. In series of laboratory experiments conducted, it was found that an optimum combination of surfactant concentration and mixing intensity was able to effectively reduce OIW size, preventing the formation of larger particles due to the reduced surface size and contact area of the oil droplets and subsequently lower injectivity risk. As a result, produced water with OIW content as high as 300 ppm can be reinjected, leading to a smaller system footprint. It is expected that this technology could accelerate the implementation of PWRI offshore. As produced water stream usually increases towards the latter years of oil and gas fields, this low-cost PWRI technology provides an enormous opportunity at matured offshore assets without substantial investment in new facilities thus favoring project economics. With the ongoing global push towards the transition to cleaner energy and zero liquid discharge, this process is contributing to the sustainable operation of upstream facilities by reducing discharge to the sea, reducing the exposure of hydrocarbon and contaminants from the reservoir to the environment, and supporting SDG12: Responsible Consumption and Production.