Designer Directional Drilling to Increase Total Recovery and Production Rates

Abstract

SPE and IADC Members Abstract The implementation of a new type of well profile. the designer profile, has resulted in increased recovery and production rates. The geologically complex Gullfaks Field (See fig. 1), located in the Norwegian sector of the North Sea, has seen significant change in the initial field development plan (FOP) as a result of the design technology. A new type of well profile was necessary to increase both total recovery and production rates from Gullfaks platforms A, B and C. Advances in steerable technology and directional drilling performance enabled a three dimensional horizontal I extended reach well profile, now designated as a designer well, to be utilized to penetrate multiple targets. This paper presents the concept. motivation, performance, results and conclusions from four designer wells used in the revised FDP. Introduction The Gullfaks Field, block 34/10 (See fig. 2) in the Norwegian sector, is the first license ever run by a fully Norwegian joint venture corporation. The license group consists of Statoil (operator), Norsk Hydra and Saga Petroleum. The field currently produces more than 85,000 5m /day of oil from three main reservoirs of the Jurassic age. The field produces from three separate Condeep (OBS) platforms; Gullfaks A, B and C. Gullfaks A and C are fully independent processing platforms with three separation stages. The Gullfaks B platform provides processing facilities for single stage separation only and transfers oil to both Gullfaks A and C for further processing. The Gullfaks Field has a very complex reservoir with numerous fault blocks and structures. Reverse faulting, in areas dominated by normal faults, accentuates the complexity of this reservoir. To date, approximately 70% of all GulIfaks wells have encountered small-scale faults not previously detected by seismic imaging, which again adds to the challenge presented by this field. Approximately 100 wells will be necessary to properly develop the Gullfaks Field according to the FDP. Generally, two producing wells are accompanied by one injector well. With the initial FDP approved in 1981 and an updated FDP approved in 1985 it is easy to understand its revision in light of the combination of technological advances and increasing knowledge of the reservoir with each well drilled. MOTIVATION FOR NEW PROFILE The initial FDP was based upon well profiles with minimum displacements of 3 km and maximum inclinations of 60. As the early production levels were below expectations, concern existed regarding future production levels on Gullfaks wells. Optimized multiple targets and optimized borehole placement were felt to be critical to improving the production rates and total recovery on the Gullfaks Field. To optimize both the targets and borehole placement, in this geologically complex field, would require substantial turn in the horizontal plane. The drilling department expressed concern about the ability to drill highly deviated wells with large turn in the horizontal plane. As steerable technology improved and the level of execution of the directional companies providing steerable motors improved as well, both management and the geology department were increasingly confident that this type of well profile could indeed be drilled successfully. P. 255^

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