Analysis Of A Polymer Well Treatment In The Beatrice Field

Abstract

Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere is usually granted upon request provided proper credit is made. Abstract A polymer injection treatment was carried out in the Beatrice field in 1985. The object of the treatment was to improve vertical sweep in the heterogeneous sands between an injector/producer pair. The process was closely monitored using a variety of standard and nonstandard techniques: tracer tests, production logging, pressure interference tests before and after polymer injection, and polymer chemical analysis in produced and backflowed brine. Subsequently, a chemical simulation model was constructed and compared with the field data. It was demonstrated from the field measurements that the polymer had a clear effect on fluid flow patterns in the reservoir. However, the simulations showed that there had been a shorter distance of polymer penetration than assumed in planning the treatment, so that the watercut changes were too small to be observed. The project is significant in giving an informed picture of polymer behaviour ill heterogeneous North Sea fields. It also successfully demonstrates the array of measurements needed to predict, monitor and reduce risk in polymer field applications. Introduction The Beatrice field is a UKCS development in the inner Moray Firth (see Fig 1). Primary reservoir energy is low and the development plan uses both waterdrive (to supplement the natural aquifer drive) and artificial lift by means of electrical submersible pumps (ESP) to recover the oil. An injection well (A23), completed in February 1985 in the Beatrice H sand (Fig 2) was found to be in very close pressure communication with its neighboring producer A8. From the start of injection in A23, it took only 17 days for injected water to break through at A8, 1150 feet away. This was evident from chloride and sulphate trends. A rapid increase in AS watercut followed from 40% at the start of A23 injection to about 92% by the end of April 1985. These results, together with interference tests, production logging and permeability measurements on core from a neighboring well, supported the following geological model: A23 and A8 lie on the same sandbar within a series of tidal river mouth sands.