Evaluation of OiW measurement technologies for deoiling hydrocyclone efficiency estimation and control

Offshore oil and gas industry has been active in the North Sea for more than half a century, contributing to the economy and facilitating a low oil import rate in the producing countries. The peak production was reached in the early 2000s, and since then the oil production has been decreasing while the water cut has been increasing rapidly. The water dominates some of the wells and a water cut of 90% is not uncommon, where all of the water has to be separated from the oil before it is discharged into the ocean. As the oil cut in the Danish part of the North Sea decreases the pumped volume is increased to reach the desired oil production capacity, consequently the discharged amount of oil increases. This leads to oceanic pollution, which has been linked to various negative effects in the marine life. The current legislation requires a maximum oil discharge of 30 parts per million (PPM). The oil in water (OiW) concentration is difficult to measure and currently is done manually and offline. This poses a challenge in continuously monitoring the actual amount of oil that is being discharged into the ocean. Our goal is to optimize the separation efficiency in a deoiling hydrocyclone, by developing a novel control technology which is based on online and dynamic OiW measurements. This article evaluates some currently available online measuring technologies to measure OiW, and the possibility to use these techniques for hydrocyclone efficiency evaluation, model development and as a feedback parameter. We additionally look at particle size measurements, as they play a big role in the separation process' efficiency.