The Deployment of Ceramic Membrane Technology to Treat Stable Oil in Emulsions in Produced Water Offshore

Abstract

In a significant number of oil and gas fields, production chemicals like corrosion inhibitors are continuously injected subsea at the wells and can cause issues with produced water quality. Corrosion inhibitors are generally injected to prevent corrosion in carbon Steel flow lines and can operate by the formation of a chemical film barrier along the interior surface of the flow line. However, when the fluids mix at the production facility the chemical interactions of the oil, inhibitor and water can create a tight emulsion that is extremely challenging to remove from the produced water. Existing water and oil separation treatment equipment is quite commonly unable to separate the water from the hydrocarbons in this emulsion as droplet sizes are often < 10 µm, resulting in produced water with non-compliant dispersed oil in water (OiW) content for overboarding. After extensive testing of a large range of technologies, ceramic membrane technology turned out to be one of the most suitable technologies to treat the produced water down to compliant levels required by the OSPAR regulations, < 30 mg/l dispersed OiW. The information that will be presented in the presentation is real-life operational data from pilot tests as well as the first of its kind full field commercial deployment of Liqtech/Semco silicon carbide (SiC) ultrafiltration membrane technology for offshore OiW removal. This first full field application will likely pave the way for further deployment of this technology in (offshore) oil and gas operations.

Modeling and Control of Membrane Filtration Systems for Offshore Produced Water Treatment

“…The porous membrane wall is a selective barrier, in terms of size, that allows passage of particles or droplets with a size less than the membrane pores. Based on case studies for PWT, the considered concentration levels suggests membrane installation either downstream the gravity separators or the hydrocyclones [16][17][18][19]. However, the higher concentration after the gravity separators causes increased fouling.…”

“…The ceramic membranes are, compared to polymeric membranes, recognized for high resilience against temperature, pressure, cleaning agents, and for a narrower and more well-defined pore size distribution [28,53,71]. However, polymeric membranes are in general lighter by a factor of 10 and are less expensive to manufacture compared to ceramic membranes, especially weight is a crucial parameter for offshore deployment [16,29,72].…”

“…A prototype for PWT with two stages was tested in [72] and based on results a four-stage membrane filtration unit was suggested for offshore PWT. Furthermore, in [16] two two-stage filtration units were tested offshore with promising results. As the produced water is treated by each filtration stage, the concentration in each loop gradually increases.…”

“…Crossflow is a well-established method, where the feed media is continuously circulated in a loop. The flow velocity over the membrane surface introduces shear preventing and removing fouling while also reducing concentration polarization (uneven distribution of the foulants over the cross-section) [16,17,105,111].…”

“…As the permeate flow and TMP are reversed during backwashing, the membranes being backwashed are consuming produced permeate. Despite produced permeate being consumed by backwashing, backwashing has shown to increase overall permeate production [16,20,[46][47][48]126].…”