Evaluation of Process Cooling in Subsea Separation, Boosting and Injection Systems (SSBI)

Abstract

The next generation of subsea process systems will combine the subsea gas compression technology currently under qualification with the previously developed subsea processing technologies, including separation, multiphase pumping and produced water re-injection. These systems will benefit from process cooling. This paper is an evaluation of the use of process cooling in subsea separation, boosting and injection (SSBI) systems including compression. Fouling is the biggest uncertainty, and potentially the biggest problem, in the design and operation of process cooling for SSBI systems when reliability, size, weight and controllability are considered as the most important design parameters. The room for optimization towards fouling reduction in the process cooling was identified to be in the process system design, in the cooling arrangement, in the heat exchanger selection and in the heat exchanger design. In each of these steps the optimization potential was identified and discussed. A case study was performed in which a direct cooling system using a printed circuit heat exchanger was found to be the most compact solution. The rate of fouling will set the reliability and maintainability of a heat exchanger installed under water. The fouling rate, and subsequently the cleaning strategy will change the design of the heat exchanger. The available information on fouling rate in SSBI systems is not complete. To develop a complete picture of fouling in subsea heat exchangers it is suggested that similar heat exchanger technology already field proven is studied for the collection of detailed operation experience and data. This infromation is useful for the design of subsea process coolers to develop the most compact, reliable and controllable solution.