Efficiency evaluation of offshore deoiling applications utilizing real-time oil-in-water monitors

An increasing water to oil ration in the North Sea oil and gas production motivates for an optimization of the current deoiling facilities. Current facilities are operated on matured methodologies, which in most cases fulfill the government regulations. However, it has also observed that these solutions could be further improved. In order to more precisely monitor the deoiling operations, this study investigated the real-time monitoring of the deoiling efficiency of the hydrocyclone facilities which are commonly used in offshore oil and gas production. Fluorescence based monitors were applied to measure hydrocyclone inlet's and underflow's Oil-in-Water (OiW) concentrations in real-time. Image-based microscopy was used to analyze the oil droplet size distribution at inlet and underflow to investigate the droplets' influence on hydrocyclone's efficiency. Performance experiments were carried out to identify how pressure difference ratio (PDR) and the droplet's sizes affect the deoiling efficiency. The performance of the deoiling hydrocyclone was significantly influenced by the inlet flow rate, while less or marginally dependent on the PDR. The droplet size distribution experiment proved that large droplets have a high probability to be separated by the hydrocyclone. The findings suggest that the coupled separator tank and hydrocyclone system can be further improved upon by deploying coordinated control as the two systems are strongly interdependent.