The Fulmar field, located in the Central North Sea, began production in 1982. This thick reservoir covering an area of only 10 sq. km has an 0IP of approximately 850 MB0 (135 × 106 m3). Initial reservoir pressure was 5700 psi (39,300 kPa) (3900 psi above saturation pressure, 2200 psi above hydrocarbon gas-oil minimum miscibility pressure, and, 1000 psi above hydrostatic pressure). During the first two years of operation, the field pressure dropped more than 1000 psi (6,900 kPa), a secondary gas cap developed because of gas injection, and the oil-water contact advanced up to 100 ft (30 m). A 3-D, 3-phase, black-oil numerical model of the field was developed in 1984 based on 27 months of production data to project future performance with alternative development and depletion strategies.

Interesting features of the simulation include: miscible gas injection into an undersaturated oil reservoir, pressure communication between fault blocks with different original oil-water contacts, the modeling of gas and water coning at wells located near the dome shaped crest of the structure, and compliance with facility, drilling and recompletion constraints, as maintained by rate and well management routines in the simulator.

A description of the 5000 block numerical model is provided along with the history match and results of simulation predictions. Conclusions drawn from this work include the following: (1) A production plateau of at least 135 kBD (894 m3/h) can be maintained until 1987 without additional drilling; (2) this plateau can be extended an additional three years through further drilling, recompletions, and re-distribution of water injection; and (3) improved oil recovery from the Clyde sand unit can not be achieved simply by modifying the production-injection strategy for that zone.

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