Advanced Geosteering Technologies to Maximize Well Design while Minimizing Costs and Risks; Marulk Field (Norwegian Sea)

The Marulk field is a gas condensate accumulation located in the Norwegian Sea. The main reservoir is Lysing Fm. (Upper Turonian-Lower Coniacian) consisting of a confined turbidite system. The secondary reservoir, Lange Fm. (Uppermost Albian–Lower Turonian) consists of heterogeneous turbiditic sands alternating shale. The Lange reservoir was decided to be targeted by one single horizontal gas production well. The planning of the well posed several critical challenges; crossing the depleted Lysing Fm. (+/-10 m uncertainty), landing 3 m inside Lange reservoir (+/- 30 m uncertainty) and optimizing the well placement inside the heterogeneous reservoir. The case studied is a great example of how use of advanced technologies in combination with a strong interaction between professionals both in the planning and execution phase, resulted in maximizing well project while minimizing costs and operational risks exposure. By use of Ultra-Deep EM directional tool a successfully global well placement operation was possible even in a highly uncertain environment and without drilling a pilot hole. As the first time on the Norwegian Continental Shelf, a Logging While Drilling sourceless Bottom Hole Assembly encompassing petrophysical logs, high resolution resistivity bore hole images and pressure measurement in one go was run successfully in oil-based mud environment.