Efficiency investigation of an offshore deoiling hydrocyclone using real-time fluorescence- and microscopy-based monitors

Offshore oil & gas production is facing an increasing challenge as the water fraction from the production wells rises over time. It is not uncommon that the extracted mixture contains a water-cut of more than 90%. The current North Sea discharge legislation states that the dispersed oil concentration in water must be less than 30 parts per million (ppm). Consequently, the discharge ports are sampled two times per day and analyzed using the OSPAR recommended GC-FID method. However, the variations of Oil-in-Water (OiW) concentration between sampling time points are unknown and could exceed the regulatory limits. This sampling method is commonly used since the current real-time OiW monitoring technology is still quite open and immature. This work focuses on experimental investigation of reliability and accuracy of selected real-time OiW measuring technologies based on two available commercial products. The obtained results indicate that the instrument based on fluorescence technology can provide reasonably fast, reliable, and accurate OiW concentration measurement, while the instrument based on microscopy technology can provide fast and reasonable measurement of the oil droplet's size distribution. This work indicates that it is beneficial to combine both technologies for real-time OiW monitoring before and after the hydrocyclone.