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^

SPE Members Abstract This paper will present recent technological innovations which have been used to surpass previous extended reach records together with other technologies which are viewed as fundamental in overcoming current limitations for extended reach and designer wells. The paper will focus on three specific drilling applications which provide a range of options for operating companies with varying field development philosophies. Introduction With records being continually broken in extended reach drilling (ERD) the obvious question is, how far can we go with existing technology? A recent well in the North Sea extended the step out record by 600. m to 7.8 km. The current limit is presently indeterminate, but as drilling technology continues to improve the final constraint may be economic rather than technical, as the limiting factors are gradually overcome. This paper will address some new technologies that will assist in increasing drilling reach and performance. Directional control and drilling efficiency are two items which have had significant impact on the decisions to attempt ERD and designer wells. The following directly contribute to improving directional control and drilling efficiency:–Tandem motors–Downhole adjustable stabilisers–Performance stabilisers The use of tandem motors offers more power than conventional motors and will increase overall rate of penetration (ROP). New intelligent multi-positional adjustable stabilisers can reduce hole tortuousity, thus extending the reach. It also allows inclination control, when drill string drag prevents further oriented drilling and maximises drill string rotation, which aids hole cleaning. A performance stabiliser, which is run below the motor, increases directional control. These technologies assist in optimising directional drilling performance. Fig. 1 represents a sample well profile that was generated to determine what capabilities were required to drill a 10 km stepout well at a true vertical depth (TVD) of 2900 m. This was an arbitrary two dimensional well profile generated to highlight potential problems in drilling such a well. As this was not based on any specific field, casing points were chosen that were feasible from a design perspective and to ascertain approximately how far out the casing could be run. The profile terminates in 8–1/2 in. hole as this is perceived to be the optimum configuration for most operators. There is obviously no unique 10 km stepout well as the complexity will depend particularly on the TVD of the reservoir which will subsequently determine the final measured depth and hole angle. This will have an impact on all associated activities including wireline logging, completion and workovers. Tandem Motors From the early days of single lobe, high speed-low torque to today's multiple lobe high torque-low speed configurations, the positive displacement motor (PDM) has become the workhorse in directional drilling. The need for improvement was driven by the operator's requirements of driving the latest bit technology and optimising drilling performance. P. 33

Constant Bank - 1 is a 3,200m (10,500ft) wildcat well located in 50m (164ft) of water on a carbonate bank in the Republic of Seychelles, a group of tropical islands in the Indian Ocean. This paper covers in detail how the contracting philosophy was developed to plan and execute the project through the formation of an alliance comprised of Operator, Drilling Contractor and Integrated Services Company. It examines the unique environmental and logistical features of this project and how the alliance sought to deal with these critical issues utilising the strengths of the respective companies to reduce risks and ensure a cost-effective, successful operation, The logistical management of planning a rank wildcat in a remote location with no practical means of resupply and no local resources was further complicated by anticipated technical difficulties with the well. The paper concludes by considering the different objectives of each company in conjunction with the overall project objectives and how these respective goals were aligned to the mutual needs of the alliance. The lessons learned by all three alliance members are noted and recommendations made on how they would approach such all operation in the future. Introduction Enterprise Oil Exploration Ltd., under a license agreement with the Seychelles National Oil Company, had a commitment to drill a subsea exploration well to a total vertical depth of 3,200m (10,500ft). The well was located on Constant Bank, 200 km (124mi) south east of the main island of Mahe (Fig. 1). Enterprise was the sole licensee with 100% equity in the well. This paper describes the various factors that increased the risks and consequently the potential costs of drilling this well. A project management strategy involving integrating all the principal services into two distinct contract groups was devised and applied to manage these risks and reduce the costs. The lessons learned from the application of this process to a high-risk remote-location single-string venture are noted and recommendations are made for enhancing this form of management strategy in future drilling operations. In addition, the limitations of this type of approach are defined. Project Outline The principal factor governing the drilling project is the well location. Located in 50m (164ft) of water on a carbonate bank 200 km2 (124mi) from the main island of Mahe and over 5,300km (3,300 mi) from the Singapore supply base, the well had a number of significant risks associated with it. The Republic of Seychelles is one of the smallest countries in the world with a population of 70,000 people living on several small granite islands totaling 280 km2 (175 mi2) in area in the western Indian Ocean. The country is renowned for its unspoiled, pristine environment with the main sources of revenue being tourism and fishing, two businesses that are usually not associated with oil exploration. These potential incompatibilities could be compounded by the company's very high public exposure in such a small country. Consequently, environmental protection was of paramount importance. Moreover, the country was devoid of any infrastructure to support an offshore exploration programme. Coupled with this, the remote location of both the well and the islands themselves meant that any resupply would be very difficult unless by air. This combination of these geographical and ecological factors resulted in the decision to use a drillship. The vessel to be selected had to have the capacity to carry all the equipment and materials for the well plus considerable contingency. Added to all the aforementioned challenges, the well was a rank wildcat and given the difficulties of resupply it would be necessary to carry substantial additional materials to allow for any unforeseen well problems. Also, the drillship would require state-of-the-art minimum-discharge systems to meet the onerous environmental restrictions imposed by the Seychelles authorities. P. 431

Constant Bank-1 is a 3,200 m ͑10,500 ft͒ wildcat well located in 50 m ͑164 ft͒ of water on a carbonate bank in the Republic of Seychelles, a group of tropical islands in the Indian Ocean. In this article we describe the development of a contracting philosophy for planning and executing the project through the formation of an alliance comprised of operator, drilling contractor, and integrated services company. We examine the unique environmental and logistical features of this project and describe how the alliance addressed these critical issues by using the strengths of the respective companies to reduce risks and ensure a cost-effective, successful operation. The logistical management of this rank wildcat well, which was situated in a remote location offering no practical means of resupply and no local resources, was further complicated by the technical difficulties associated with the well.We conclude by discussing the different objectives of each company in conjunction with the overall project objectives and describing how these respective goals were aligned to the mutual needs of the alliance. The lessons learned by the alliance members are noted and recommendations are made for approaching similar operations.

This paper was~paredfor presentation al the 1998 lADC/SPE Asia Pacific Drilling Conference held in Jakarta, Indonesia, 7-9 Septembr 1998, This paper was s~ec[ed for presentation by an [ADC/SPE Pr@ram Commiftw following review of information cnnlained in en abstract submitted by the author(s). Contents of the paper, as presented, have not been revjewed by the International Association of Driffing Contractors or the Society of Petroleum Engineers and are subject to correction by the author(s) The material, as presented, does not necessarily reflact any~sition of the IADC or SPE, their oficers, w members. Papers~esented at the IADCISPE maatings are subject to publication review by Editorial Committees of the IADC and SPE, Electronic reproduction, d!.stnbution, or stcfage of any part of this paper fof mmmercial purposes without the written mnsent of the Society of Petroleum Engineers is prohibited Permission to reproduce in print isresk!cled to an abstract of not more than 300 words, illustrations may not b mpied The abstract must mntain conspicuous acknowledgment of whare and by whom the paper was presentd Write Librariw, SPE, P 0, Box 833836, Richardsm TX 7S083-3B36. U. S.A., fax 01-972-952-9435. Abstract