Single-Diameter Technology Capable of Increasing Extended-Reach Drilling by 50%
Authors: Bybee Karen 
Published: February 2015

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 17828, "Single-Diameter Technology Capable of Increasing Extended-Reach Drilling by 50%," by R. Bell, R. McKee, and E. Zwald, Enventure Global Technology, and D. Lewis, SPE, and P.V. Suryanarayana, SPE, Blade Energy Partners, prepared for the 2006 Offshore Technology Conference, Houston, 1–4 May.
The combination of single-diameter technology and extended-reach drilling (ERD) can have a positive effect on capital-cost structure. Single-diameter technology provides the foundation for a significant increase in the lateral reach of many extended-reach wellbores. This extended lateral reach results in increased reservoir contact that can lead to increased production per well, which can reduce field well counts.

Introduction
Solid expandable tubulars (SETs) have evolved over the last few years into a proven openhole-drilling-liner and cased-hole-remedial-liner alternative to conventional technology. A well-design feasibility study was conducted as part of the front-end engineering and design for a major North Sea operator. The study was performed to evaluate the relative merits of using conventional drilling technology vs. expandable-tubular technology for lateral reach and the effect on capital efficiency and potential field development. This well-design study indicated potential lateral-reach increases of 25 to 100%. Drilling-performance and cost studies indicated that existing and planned well costs and times in the same North Sea fields could be reduced by more than U.S. $40 million or 30 to 50% of the current drilling cost and time.

Expandable ERD Well Design
An existing North Sea oil development project and a planned subsea gas development project were used to evaluate and quantify the lateral-reach improvements possible with SETs. An in-house program was used for drillstring mechanics, stress analysis, and fatigue analysis that included operator-provided drilling and completion data, lithology, mud parameters, torque and drag, and well designs. Historical data provided a baseline for ERD in the subject fields and a context for estimation of trouble times and expected time to drill extended-reach wells as long as 50,160 ft. The current lateral-reach record in the North Sea field is approximately 26,400 ft, with significant drilling trouble.
All aspects of SETs and single-diameter liners were considered in the context of ERD beyond conventional-technology limits, including the unique force transmission during expandable-technology operations. Optimal well paths were planned by use of constrained optimization methods. Wear analysis was based on an adhesive-wear model that is the basis of all industry wear-analysis programs. Casing integrity was evaluated with the working stress design approach (deterministic design) and supplemented by probabilistic design where appropriate. Drag risk was evaluated.
The base well-design model evaluated the achievable lateral reach and drilling-trouble reduction with the following.Conventional drilling technology.Conventional technology with improved drilling practices.Installation of two SET liners to preserve the desired completion size.Installation of multiple, successive single-diameter drilling liners.