ExxonMobil, as operator for the Sakhalin-1 project, recently planned a drilling campaign at the Chayvo Field, Sakhalin Island, Russia. The focus of this campaign is the development of a thin oil column reservoir using extended reach drilling (ERD). This paper will provide an overview of the planning of these challenging wells at the edge of the ERD envelope, the associated technical and operational challenges, and the additional complexity of targeting a thin oil column in an ERD environment. Significant well design parameters, tools, and techniques to enable these challenging wells will be presented. Results to date from this drilling campaign will also be presented.
ERD has become a commonly used technique to economically access reserves from existing infrastructure and to reduce the facilities environmental footprint. The case history described in this paper illustrates the combination of planning, technical design, and operational practices required to push the ERD envelope further.
The distance of the reservoir from shore resulted in planned well lengths at the edge of the ERD envelope. Planning of these record wells involved building upon the Operator's previous experience as well as additional tools and methods to address the unique challenges. The technical challenges included uncertainties in the location of the oil column and fluid contacts, very accurate well placement for effective reservoir drainage and preventing early gas/water breakthrough, completing long horizontal intervals, and high torque and drag. The geologic uncertainties and wellbore positioning challenges were addressed using a combination of a single near horizontal pilot hole to locate both fluid contacts and a novel technique to minimize vertical position uncertainty using formation pressure measurements while drilling. Extensive torque and drag and wellbore stability modeling were performed to design the wells, operational parameters, and equipment. Completion designs were optimized to ensure successful placement in long horizontal intervals.
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