Flow Induced Inline Separation (FIIS) De-watering Tests at the Gullfaks Field

Abstract Several fields on the Norwegian Continental Shelf have reached the decline phase with an increasing production of water and gas, often in combination with reduction in reservoir pressure. The available space and weight allowance for installation of new equipment on the platforms is often limited, and it is important to minimize both the operational and capital costs. Compact, inline separation equipment can be a key technology for mature fields, and also for subsea fields at large water depths where the weight is critical during the installation phase. The Statoil operated Gullfaks license has identified Flow Induced Inline Separation (FIIS) as a key technology in order to increase the oil recovery. Due to low foot print, low hydrocarbon inventory and reduced need for flare capacity, the resulting reduced operating cost of the technology, can aid prolonged production from the reservoir. The technology will also provide free space and weight allowances for future tiebacks to Gullfaks. A survey identified a need for both compact gas-liquid as well as compact oil-water separation. Statoil have chosen to develop and test relevant units in close co-operation with vendors of compact separation equipment. All the tested technologies are based on cyclonic separation equipments with low or moderate pressure drops. Statoil is carrying out an extensive qualification program where compact oil-water separators from FMC Technology and Caltec are developed and tested at real operating conditions. Individual unit tests (25 Am3/h, 3770 bpd liquid) have been performed in high pressure laboratory flow loops and in a test rig on the Gullfaks C production platform located in the North Sea. The aim is to remove at least 60 % of the incoming water phase with a water quality acceptable to the downstream produced water system. The operational window of the tested cyclonic technologies is wide for both vendors. The effect of gas content, water cut, droplet size, operating pressure and water removal on the outlet water quality will be described in the paper. The conclusion from the work is that the potential of compact oil-water separation is large and possible applications will be discussed in the paper.