Expanding Oil Field Tubulars Through a Window Demonstrates Value and Provides New Well Construction Option
Authors: Sparling Steven W. , Noel Greg 
Published: October 2008

The oil and gas industry has remained somewhat cautious of the concept of solid expandable tubular technology since its inception more than four years ago, especially in deep water. Most drilling operators prefer to stay within their own comfort zone and let others explore the boundaries of any new technology. In nearly all of the 200-plus installations to date, solid expandable tubular systems have been deployed as eithercased-hole liners, entirely inside an existing tubular, or as a drilling liner protruding from the shoe of an existing string into open hole. However, those operators pushing the boundaries of this new technology are exploring the benefits of utilizing expandables through sidetracks. Exiting through milled windows while maintaining a useable inside diameter (ID) is very attractive to operators for re-entries or in just reaching the planned depth in areas where drilling encounters unusual challenges.

When solid expandable tubulars are installed in conjunction with sidetracking operations in existing wellbores, the potential benefits are the following:The presence of an existing well reduces the cost to re-drillPotential for an extra casing string with minimal loss of inside diameterBigger hole size at total depth These and other advantages make re-entry using solid expandable tubulars a more attractive option for most operators.

In addition, operators with mature fields can deploy solid expandable tubulars through milled windows in existing wells to reach previously unrecoverable reserves. The technology will enable operators to utilize an existing well in fields where new infill wells are uneconomical.

This paper will use case studies and field trials to demonstrate that solid expandable tubular technology can be installed through a window exit. In addition, this paper will provide evidence that this new technology gives deepwater operators another viable and unique option to evaluate prior to abandoning a well.

Introduction

Solid expandable tubular technology allows operators to reach reservoirs that cannot be reached using conventional technology. As the technology matures, new applications are continually being discovered and implemented.1 The first wells in which solid expandable tubulars were applied were typically simple vertical wells or wells that required some form of simple remediation, such as the repair of deteriorated casing. The move to more challenging wellsp rogressed steadily as lessons learned led to system enhancements. This steady progression has not only resulted in a more reliable product but also has increased operator acceptance and use.

The natural progression of the technology has led to solid expandable tubulars being introduced into deviated, difficult wells. Operators experience a myriad of issues when drilling and casing a well, often prompting the decision to sidetrack. When conventional technology is used to sidetrack, these issues cause the operator to lose an entire casing size, reducing the size of the hole in the production zone and restricting the flow of oil through the well and further decreasing the wellâ??s economic viability.

When faced with the potential plugging and abandoning of a mature well, operators may sidetrack from an existing well and search for a new target zone. This procedure is often the only alternative to drilling an entirely new well to reach another target.