Increasing Sakhalin Extended-Reach-Drilling and -Completion Capabilities

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 119373, "Increasing Sakhalin Extended-Reach-Drilling and -Completion Capabilities," by Michael W. Walker, SPE, Andrew J. Veselka, and Shane A. Harris, SPE, ExxonMobil, prepared for the 2009 SPE/IADC Drilling Conference and Exhibition, Amsterdam, 17-19 March. The paper has not been peer reviewed. Extended-reach-drilling and completion capabilities at the Chayvo field, Sakhalin Island, Russia, have evolved in well-design and operational practices to increase well reach to more than 10.5 km. Disciplined redesign has been based on learnings acquired through-out the program. Learnings and design changes were applied to Well Z-12. Introduction The Chayvo field is on the northwest coast of Sakhalin Island, where operations must contend with harsh arctic winters and limited infrastructure. The field is a gas-filled anticline having an oil rim that is the current development-program target. The field is developed with horizontal completions from the Yastreb land location and from the Orlan offshore concrete-island drilling and production platform. Production from both wellsites is delivered to an onshore production facility, with oil subsequently delivered to tankers in protected waters off the Russian mainland. Most of the produced gas is reinjected to assist reservoir-pressure support, with lesser amounts consumed as fuel or sold. During Chayvo development drilling, wells became increasingly complex. Longer throws have resulted in higher demands on rig equipment (especially the top drive and drillpipe) and have made successful placement of completion equipment more challenging. Twenty-one wells have been drilled and completed (17 oil producers, three gas-injection wells, and one cuttings-injection well). Z-12 Case History Well Z-12 has an ultimate total depth (TD) of 11 680 m measured depth (MD). Drilling operations on were completed in January 2008, and the well reached TD in 68 days. The well, on the north end of the Chayvo field, was designed to encounter potential productive sands on both the western and eastern flanks of the field. Previously drilled Well Z-11 had similar objectives but encountered significant difficulties with hole instability and placement of the production liner. After analyzing learnings from Well Z-11, several areas were determined as critical to the success of Well Z-12. Wellbore stability balanced against equivalent-circulating-density management in the 8-in. hole. Successful placement of the completion liner in the 8 1/2-in. hole and the use of a designer running string. Torque management facilitated by a smooth wellbore trajectory and use of lubricants. Optimized rate of penetration (ROP) and improved bottomhole-assembly (BHA) life through application of the operator's drilling-performance-management system.