A New Method for Removal of Oil in Produced Water

Abstract

SUMMARY Produced water represents an increasing part of the total production from the process centres in the Danish part of the North Sea. Experience gained with treating the increased volume of water led the operator, Maersk Oil and Gas, to evaluate the possible application of centrifuge technology. In the produced water from the Tyra formation, the size and distribution of oil droplets were found to be of a character that conventional treatment equipment would have difficulties in separating efficiently. After having tested a rented centrifuge for one year on the Tyra West installation, it was decided to purchase centrifuges for permanent installation on both Tyra East and Tyra West. At the end of 1992 and beginning of 1993, the 12,000 BWPD centrifuge skids were installed and commissioned on each of the platforms. Experience from the installation, commissioning and first 6 months of operation has been encouraging. No major problems arose from the integration of the quite complicated equipment and control system with existing installations on the platform. The complete produced water treatment plant modifications were minimal due to the relative simple requirements from the various tie-in points on the centrifuge skid. The oil in water measurements of the cleaned water out of the centrifuges comply with the Paris convention requirement of maximum 40 mg/l, usually with a large margin. A comprehensive PLC control and communication system to the Platform Control Room performs as planned. The monitoring features available have shown to be beneficial in achieving uninterrupted centrifuge operation. The application of centrifuge technology has shown to be environmentally valuable as well as a very effective way of treating produced water which contain small oil droplets.