Solid Expandable Tubular System Mitigates High-Pressure Zones with Record Length

Abstract

Dealing with higher than planned pore pressures, slim drilling margins and depleted zones in the same wellbore can quickly compound an already difficult deepwater drilling environment. Current market demands for oil and gas are placing more focus on deepwater development of existing reserves. Operators have had to utilize enabling technologies that are robust enough to address multiple problems to develop deepwater reserves that are difficult to access. This paper describes a recent example of this dilemma when a deepwater operator successfully employed a solid expandable tubular system to isolate both overpressured and depleted sands The solid expandable system facilitated reaching the well objectives with a large hole size for maximize production rates. Over 6,865 ft (2,092m) of 7–5/8 x 9–5/8 in. expandable openhole liner allowed the operator to drill through both overpressured and depleted sands to an intermediate and unplanned casing point. Subsequent drilling operations below the expandable liner enabled the operator to reach the target zone and case the well with a 7 in. flush-joint production liner. Without the expandable installation, the operator would have been restricted to a maximum 5–1/2 in. casing at total depth (TD). Comparatively, 7 in. casing allowed the use of larger completion equipment providing Nexen Petroleum U.S.A., Inc., with significant additional production while reducing the mechanical risks associated with working inside smaller casing. The solid expandable tubular operating envelope provides a robust technology for operators who need a responsive system that addresses conditions proven to hinder drilling objectives. This paper will describe the conditions that led to selecting the solid expandable solution and detail the challenges mitigated with the installation of this record-setting system. In addition, this paper will focus on how solid expandable tubulars are applicable in extremely difficult drilling conditions and also how these tubulars can reduce the risks and costs associated with deepwater drilling. Introduction Deepwater Gulf of Mexico (GoM) was a fitting location for this record-length installation of a solid expandable tubular system from a semi-submersible (Figure 1). With the first expandable system installed in a shelf well just south of Louisiana state waters, the GoM was also the location of the first deepwater installation. The move to deeper water in the GoM was a natural progression for expandables as the technology has become more readily available and reliable for achieving extreme objectives. In its fundamental form, solid expandable technology reduces or eliminates the tapering effect of consecutive casing strings, preserving valuable hole size. An application history compiled since inception in the late 1990s has proven these systems as a technology that enables operators to reach and produce reserves previously unattainable due to drilling conditions and economic constraints. These systems have provided flexibility for well uncertainties and have helped operators reduce well costs with a slimmer well design.1&2 This design approach provides an alternate option to the big-bore well that results in a finite number of casing strings that can be used to reach the production zone. Removing this limiting drilling aspect helps reduce the risk of difficult oil recovery, and operators are reconsidering reserves that are now more attainable.