The Don Field lies in the north-east comer of Block 21 l/18a approximately 15km north of the Thistle Field. The reservoir comprises the Middle Jurassic Brent group of sands and consists of several discrete hydrocarbon accumulations.

The appraisal well data portrayed a complex hydrocarbon bearing structure with considerable uncertainties regarding the degree of faulting, reservoir quality, connectivity and hydrocarbon fluid properties. This pointed to a phased sub-sea development tied back to the Thistle platform, which would allow for systematic reduction of risks, balancing of cash exposure, and lead ultimately to an optimum reservoir management strategy for the field.

First oil flowed in October 1989. Initial performance of the first wells has shown the Don NE reservoir to be highly faulted, and divided into a series of poorly connected compartments. This complex structure severely reduces areal sweep, and recovery from the initial wells will be considerably less than originally predicted.

The paper discusses how the development well results and production monitoring have led to a revised reservoir description of the field. The flexible nature of the Don concept has allowed the development strategy to be modified to accommodate the outstanding reservoir uncertainties, whilst maintaining sufficient production to make effective use of the current facilities.

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