TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFor years, offshore shuttling to accommodate insufficient bed-space has invoked a safety risk for offshore workers. A North Sea operator has overcome this by implementing tools to dramatically change the normal work flow in decision making.

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Development of formation evaluation technologies for azimuthal, deep-reading measurements and accurate and flexible 3D rotary steerable drilling systems have made it possible to provide truly proactive well placement. Real time use of new and advanced LWD data in horizontal drilling gives the opportunity to extend the envelope for well planning and reservoir information gathered in a single run. Optimum interpretation from real time data acquisition facilitates a reformation of the way horizontal wells are planned and drilled. This paper shows a well where the information was extracted and included in the decision making process to an extent that sets a new industry standard. Applying an accurate 3D rotary steerable system with openhole sidetrack capabilities increase well design flexibility and the ability to act on the real-time LWD data. The bottom hole assembly used consisted not only the standard LWD services such as gamma ray, propagation resistivity, density, neutron porosity and LWD gamma ray and density imaging services, but also formation pressure testing while drilling and the newly introduced azimuthal propagation resistivity. The azimuthal propagation resistivity provides unique information of the approaching bed and fluid contacts. Verification or change of the geological model during drilling through comprehensive use of forward resistivity modeling and real-time geological interpretation based on both the newly introduced azimuthal propagation resistivity service and resistivity from multiple depths of detection as well as wellbore images from both density and gamma ray, give a solid and enhanced base for real time well placement in horizontal drilling. The horizontal interpretation of resistivity data together with structural interpretation of image data gives an unmatched understanding of the geology and aids in placing the well better. Horizontal real time wellbore placement is then accompanied by real time reservoir characterization through real time formation pressure measurement to validate any fluid movements and fluid compartmentalization of the reservoir. This paper is based on wells drilled in a chalk field in the North Sea where real time data acquisition plays a significant part and illustrates to what level LWD data can facilitate proactive well placement and comprehensive reservoir characterization. Introduction The Ekofisk Field is located in the southernmost part of the Norwegian North Sea (Fig. 1) and was discovered in 1969. It is one of the North Sea Giants with a STOIIP of 7 mmbo. The field was put on production in 1971, and has been through several phases of development and re-development. The most important event in the Ekofisk field history was the implementation of the Water Injection Project in 1987, which brought the production from 70,000 bopd to above 300,000 in 2005. Current production at Ekofisk is about 270,000 bopd.

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