Deepwater Expandable Openhole Liner Case Histories: Learnings Through Field Applications
Authors: Grant Thomas P. , Bullock Michael D. 
Published: October 2008

The first commercial installation of a solid expandable tubular drilling liner in a Gulf of Mexico well in November 1999 signaled the arrival of a new technology for improving reservoir performance. Since that time, more than 40 installations have been completed. Solid expandable tubular technology offers new options in drilling, completion, and workover operations that enable operators to reach target zones that may have been previously unreachable, to increase initial production, and to extend production life through either the remediation of existing payzones or the ability to access new, potentially productive formations.

The capability to expand solid tubulars downhole can reduce the tapering effect that occurs when using multiple casing strings in deepwater drilling, conserving valuable hole size. Conserving hole size, or diametric efficiency, allows additional pipe strings to be deployed to drill deeper or (in the case of extended-reach wells) farther, or to produce target zones through larger diameter production tubulars.

Deep water, where considerable wellbore challenges exist, also holds the largest potential for value creation using solid expandable openhole liners. Wellbore diametric efficiencies are important when water depths are less than 1,500 ft, but become critical past the 5,000-ft mark, where eight to ten strings of casing are often required. Even designing well plans for this number of casing strings does not ensure that total depth can be achieved.

Solid expandable tubulars have been used to minimize well slimming while adding strings for needed depth. This paper reviews several case histories of wells drilled in water depths less than 1,500 ft, as well as some drilled in water deeper than 5,000 ft. Discussions include lessons learned from both successful and unsuccessful solid expandable tubular installations.

Overview

Four case histories describing five openhole liner installations in the Gulf of Mexico will be reviewed. The first case history describes two ultra-deepwater installations that minimized the reduction in casing size while reaching total depth (TD) with an optimum hole size. A re-rentry well with an offshore Gulf of Mexico shelf location is the second case history reviewed. This openhole liner installation provided optimum hole size at the completion of this well. The third and fourth case histories describe two applications in one ultra-deepwater well that isolated a low frac gradient hole section. These installations allowed the well to be drilled ahead to the prospective pay zones.

Case Histories

Case History Number One: Minimizing the reduction in casing size in order to reach total depth.

The operator had previously drilled an ultra-deepwater well (7,790-ft water depth) that required more casing strings than anticipated. Setting successive strings higher than the prognosis called for resulted in a much smaller hole than anticipated before reaching the well's planned total depth. The additional casing strings were needed to take care of low drilling margins that were encountered.