TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractTwo challenges facing operators as the energy industry moves into the next century are accessing of new reservoirs that currently cannot be reached economically and maintaining profitable production from older fields. Recent advances in one of the oldest and most fundamental areas of exploration and production, namely tubular technology, will play a key role in meeting these challenges.A method has been developed whereby the diameter of solid tubulars can be expanded downhole. This paper will describe the process and how this significant technological breakthrough provides cost-effective solutions to several tubular problems that have loomed as obstacles to comprehensive reservoir exploitation. In deepwater and subsalt environments such as the Gulf of Mexico, the ability to expand casing and tubing in-situ enables hole-size maintenance and conservation of internal tubular diameter for increased efficiency. Hence, operators are less likely to run out of hole diameter before evaluating all pay zones. Operators can now use smaller holes to drill deeper vertical wells or to extend the reach of deviated wells to access untapped reservoirs. In older fields, existing wellbores can be retrofitted with expanded tubulars for repair purposes or to increase strength and integrity. In the latter case, deeper high-pressure objectives can be supported, and thus, new in-fill wells can possibly be reduced in number or even eliminated.In addition to a description of the process employed to expand solid tubulars, the paper will present applications of expandable tubular technology and results of large-scale testing that has been conducted in support of the applications. Potential commercial applications are also presented.

This paper was prepared for presentation at the 1999 SPE Annual Technical Conference and Exhibition held in Houston, Texas, 3–6 October 1999.

As the oil and gas industry has matured, three broad-reaching and long-standing issues that affect virtually every well have assumed heightened importance: conservation of hole size, hydraulic isolation of selected zones, and maximization of well life. All of these issues involve one of the industry's most fundamental technologies, wellbore tubulars. Until recently, resolving these issues with conventional tubular technology was becoming ever more difficult, especially in deep-drilling and extended-reach applications, in wells utilizing liner hangers, and in aging wells containing deteriorating casing. A revolutionary new technology—expandable tubulars—has recently been introduced and has successfully addressed these issues in commercial applications. The basic concept underlying expandable-tubular technology is simple: a mechanical expansion device, known as an expansion cone or mandrel, is propagated through downhole tubulars utilizing hydraulic pressure. The progress of the cone expands the tubulars to the desired internal and external diameters in a plastic deformation process known as cold drawing. In drilling applications, a specially-designed liner hanger utilizing the new expandable-tubular technology conserves hole size by eliminating the need for a conventional liner hanger/liner hanger packer, and provides a superior pressure seal compared to the old technology. In cased wells, expandable casing is cladded to existing casing, either to repair or strengthen the existing casing, with minimal decrease in wellbore inside diameter (ID) and flow potential. Expandable tubular solutions have been successfully installed in the Gulf of Mexico, in U.S. inland wells, as well as in large-scale field trials. This paper briefly describes the technical concepts upon which expandable tubulars are based and gives an overview of expandable-tubular applications. The paper then focuses on the most recent field installations, including systems installed during the first quarter of 2000. Discussions of field examples will contain customer objectives, job design, installation procedures, ultimate results and best practices learned. Technology Overview Previously published papers have discussed the concepts of Solid Expandable Tubular (SET) technology1 and the effect of the expansion process on the system's tubulars2,3 and connectors4. In this light, the basics of SET technology will be reviewed, and the emphasis will be on how to best apply the early products of this new technology. Through the review of several case histories, it will be demonstrated how Solid Expandable Tubular products were used to cut drilling costs, to rejuvenate plug-and-abandon (P&A) candidates, and to bring more exploration and development dollars to the bottom line. The Expansion System Operation The underlying concept of expandable casing is cold working steel tubulars to the required size downhole - a process that is mechanically very unstable by its nature. Thus, there are many technical and operational hurdles to overcome when taking cold drawing processes and accomplishing them in a downhole environment. The Expansion System Operation The underlying concept of expandable casing is cold working steel tubulars to the required size downhole - a process that is mechanically very unstable by its nature. Thus, there are many technical and operational hurdles to overcome when taking cold drawing processes and accomplishing them in a downhole environment.

Establishing and maintaining hydraulic integrity between liner hangers and the base casing in which they are set has long been one of the most problematic areas facing operators. With failure rates on pressure seals in overlaps now exceeding 40% in some regions, the need for a solution to this decades-old problem has reached a critical level. Although new approaches have included turbolizers for cementing overlaps, special cements, and liner-top packers, many problems still remain. An operator and a service company are working together to develop a new drill liner hanger based on patented expandable-casing technology. This technology is being used to diametrically expand solid tubulars for a variety of drilling, completion, and remedial applications. The new liner system is designed to totally eliminate the liner lap by expanding an elastomer-coated casing into intimate contact with the casing from which the liner is being hung. Preliminary results indicate the new hanger design can result in load-carrying and burst capacities that exceed the capacity of the previous casing string. Furthermore, the overlap samples tested to date have all resulted in annular seals that have exceeded 10,000-psi differential capacities. In fact, casing has always failed during large-scale testing before any overlap leaks developed. This paper discusses the design and application of the new liner hanger and presents laboratory and field-test results. Introduction One of the long-standing challenges facing operators during well construction has been the establishment and maintenance of hydraulic integrity between liner hangers and the casings in which they are hung. In recent years, liner-top packers have been used to establish a pressure seal immediately above the liner hanger, while traditionally cement has been used to establish a pressure seal in the casing/liner overlap directly below the hanger. However, both methods of creating hydraulic integrity have frequently been unsuccessful, often because of inherent weaknesses in the design of conventional liner hangers (Fig. 1). A recent informal survey of several Gulf of Mexico operators revealed, for example, that 30 to 50% of the pressure seals in overlaps failed. Such failures not only reduce the effectiveness of the applications for which the liners are intended, but they also increase well costs because of the remedial operations that must be undertaken.

Solid expandable tubulars have been used to assist in the success and slimming of deepwater wellbores over the past two years. The expandable openhole liner system expands and seals the outside diameter of an expandable casing against the inside diameter of a string of conventionally set casing, thus slimming the wellbore compared to conventionally cased wellbores. Further slimming of wellbores was realized with the capability of expanding and sealing sequentially installed expandable casing strings, or "nested" expandable liners. This procedure decreases reduction of a typical hole size by approximately 50%. Nesting was the next step in the evolution of creating a monodiameter system, that is, a wellbore that has the same inside diameter from surface to total depth (TD). The first nesting of two expanded casings in a well was successfully completed in a drilling application in the Summer of 2001, a milestone toward creation of the monodiameter wellbore. Using nested expandable systems facilitates the employment of smaller, more economical drilling vessels to drill deepwater wells (wells drilled in water depths of 1,500 to 10,000 ft). The monodiameter system is created when the junctions of the nested expanded casing liners are "over-expanded, resulting in a single internal diameter (ID) wellbore. This type of well exhibits the ultimate diametric efficiencies" a constant ID from the top of the well to its TD. The first monodiameter "over-expanded" sealed liner overlap was produced in the lab in late 2000, opening the door for the creation of the monodiameter drill liner, followed by the production-quality monodiameter liner system. This paper reviews the evolutionary steps taken to date toward the realization of true monodiameter technology and discusses the installations that have served as milestones. This paper also discusses the potential savings realized when wellbores are slimmed using expandable systems, combined with more economic drilling vessels and the associated reduced spread-rates. Technical Evolution Solid expandable tubular technology essentially changes how to install the main load-carrying member around which all well designs are built, namely, the casing. The monodiameter system became a feasible idea with the advent of successfully expanding solid tubulars. This revolutionary concept was proven with the successful expansion of solid tubulars (initially automotive steel) by forcing an expansion cone through the tubular with hydraulic pressure and expanding it ?20%. After demonstrating conceptual proof, attention turned to refining the existing materials to address specific downhole conditions. These developments consisted of replicating desired automotive steel properties in Oil Country Tubular Goods (OCTG), changing the cone material makeup from a combination of ceramic and steel to one of all steel, and replacing welded connections with specially threaded, expandable connections. L-80 casing was developed with exceptional fracture toughness in order to achieve consistent success of expansion without pipe body failure.