Field Test of Compact Cyclonic Technology for Separation of Gas/liquid and Oil/water at The Gullfaks Field
Authors: Knudsen Borre Leif , Bjørkhaug Magne , Johannesen Bente , Ottøy Magnar , Sørensen Øystein , Eidsmo Gro Sandstad , Bruun Tor 
Published: July 2010

Several fields on the Norwegian Continental Shelf are in the decline phase with an increasing production of water and gas, often in combination with reduction in production pressure. The available area and weight 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 devices can be a key technology for mature fields, and also for subsea fields at large water depths where the weight is critical.

The Statoil operated Gullfaks licence has identified compact separation as a key technology to increase the oil recovery. Due to low foot print and low operating cost the technology can aid prolonged production from the reservoir. The technology will also make it easier to use the existing infrastructure at Gullfaks for tie-in of new fields. A survey identified a need for both compact gas/liquid as well as compact oil/water separation. Statoil has chosen to test and develop relevant units in close co-operation with vendors of compact separation equipment. All the tested technologies are based on cyclonic separation devices with low or moderate pressure drops.

Statoil is carrying out an extensive qualification program where selected compact solutions for several unit operations are developed and tested at real operating conditions. The tests have been done in high pressure laboratory flow loops as well as offshore at the Gullfaks field. The compact technology has been tested for a wide operational window, showing that efficient processing of well stream can be achieved using compact separation equipment.

The results from this work leads to the conclusion that compact technology has a large potential both in replacing conventional gravity separators topside and for deep water subsea separation.

Introduction

Several oil fields world wide are in the decline phase with an increasing production of water and gas, often in combination with reduction in production pressure. Increasing water cut means that water occupies a large part of the separator volume, which otherwise could have been used for 3rd party processing or for low pressure production. Due to low weight, low foot print and use of piping code, compact separation units can provide new processing capacity at existing installations as well as debottlenecking of existing separation equipment.

The Norwegian offshore field Gullfaks is one of the fields that have reached tail-end production. They started up in 1986 and with a peak production of 600.000 bpd oil in 1994. In 2008 the oil production was reduced to 92.000 bpd. The Gullfaks field consists of three concrete platforms, see illustration in Figure 1. The oil is stored in the concrete cells and loaded into shuttle tankers on the field, while associated gas is piped to the Kårstø gas treatment plant on the Norwegian west coast, and then further to continental Europe. Three satellite fields have been developed with subsea wells remotely controlled from the Gullfaks A and C platforms. The recovery factor on Gullfaks is 59 per cent, however the aim is to increase it to 62 per cent.