Abstract

Prior to 1995, sand production from the non-gravel packed wells and low productivity from a gravel packed well were factors which impacted the potential development of the Ewan Field, offshore Nigeria. To make the field a more attractive development candidate, horizontal and frac-pack completions were recommended. This paper compares the results of the first frac-packed well, which was expected to improve both production rates and ultimate recovery, with the previous gravel pack completion. Pressure build-up and production data show the improved productivity obtained after frac-packing. The results from the first frac-pack were so encouraging that field development includes frac-pack completions for all non-horizontal wells.

Introduction and Background

Ewan Field is located in Oil Mining Leases 49 and 95 of NNPC/CNL's Western Niger Delta acreage. The field was discovered in 1980 by Ewan-1 which encountered over 100 feet of net oil in four sands.

Ewan-2 appraisal well was drilled in 1981. A short duration flow test in the main reservoir (C-02 sand) reported approximately 1000 BOPD of 23° API oil at 200 SCF/STB GOR. The well could not be flowed at higher rates due to sanding problems. Ewan-3 appraisal well was also drilled in 1981 but was not flow tested.

Ewan-4 was drilled in 1992 to delineate the down-dip limit of the C-02 reservoir and it was completed in the C-02 reservoir with a single gravel pack. A Drill Stem Test (DST) immediately following the completion flowed 420 BOPD of 20° API gravity oil on 24/64 inch choke. The well test analysis indicated a skin factor of +70, which was the result of formation damage induced during the gravel-pack completion.

Consequently, in 1994 an acid stimulation job was carried out in the well. The well production rate improved to 750 BOPD on a 40/64 inch choke and the skin factor was reduced to +16.5.

Because of the need for sand control and higher producing rates, a frac-pack completion was recommended for Ewan-2 in an attempt to stimulate and improve the deliverability from a vertical well.

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