ABSTRACT: The Ness Field: An Integrated Field Study

R. M. Karasek, K. R. Kean, M. L. Richards

The Ness oil field, located in UK Block 9/13, was discovered in May 1986 by well 9/131b-28A. The field comprises a high-quality Middle Jurassic reservoir with an average 148-ft oil column trapped in a west-dipping, fault-bounded closure. The oil is substantially undersaturated. The field was brought on production as a subsea satellite development tied back to the Beryl B Platform. Oil was first delivered on August 11, 1987, just over a year from discovery. Initial producing rates from the 9/13b-28A well averaged about 10,000 BOPD. Since this well, another producer and water injector have been completed.

Based on the frequent and accurate pressure data available from permanent downhole gauges installed in all three wells of the Ness field, material balance was used to calculate initial oil in place. These calculations gave an oil in place value consistent with recent calculations of 87 × 166 STB after less than 3% of the oil-in-place had been produced, compared with 55 × 106 STB initially mapped. Pressure monitoring enabled reservoir drive mechanisms to be tracked and a high offtake rate to be maintained by balancing water injection with withdrawals.

A reevaluation of the mapped structure was prompted by a revision of the geological model following the 9/13b-38/38Z appraisal wells, together with the discrepancy between the oil in place from mapping and material balance. The seismic data was reinterpreted using the additional well control, and the field remapped. This resulted in a revised volume of 129 × 106 STB. Additional insight into the differentiation between oil and water volumes in this low compressibility system and a resolution of the differences between material balance and volumetrics were obtained through a black-oil simulation.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990