スノーレ油田での資産価値最大化への取り組み

抄録

The Snorre field is located in the northern part of North Sea, about 150km west of Floroe on the Norwegian west coast and in water depth of 300-350 meters.
The field was developed in two phases because of complex reservoirs. Stochastic reservoir modeling techniques were developed and applied for modeling Snorre field. Phase 1 was installation of the TLP (Tension Leg Platform) and 6km away, the subsea production system (SPS) in the southern part, and put on stream in August 1992 with water flooding as the primary recovery mechanism.
Phase 2 was installation of a SSPV (Semi-Submersible Production Vessel) in the northern part, and put on stream in June 2001.
For several years, gas injection was not applied, because only associated gas injection could not maintain reservoir pressure sufficiently. In February 1994, a WAG pilot test was initiated. WAG was well known techniques for improving oil recovery, but Snorre field was the first applied case
in North Sea area.
The evaluation of the WAG project showed that early gas break through might be a potential problem. Then, the use of foam for gas mobility control, gas shut-off and to improve of sweep efficiency had been considered as a means of improving the WAG process. Foam Assisted WAG (FAWAG) pilot test had been conducted in the period 1998 to 2001.
For gas front monitoring, 4D (time lapse) seismic surveys were carried out in 1997 and 2001. These results were used for history matching of the reservoir simulation, and optimizing in-fill well locations.
Horizontal wells were applied for both producers and injectors. And as an intelligent well completion, DIACS (Downhole Instrumentation And Control System) was applied for Snorre field. The functions of DIACS are not only monitoring the reservoir pressure/temperature, but also changing the downhole choke size.