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.

A drilling mechanics sub has been developed to measure the dynamic collar forces, accelerations, and fluid pressures just above the bit. These quantities can be transmitted to surface using mud pulse telemetry to provide the driller with real time information about downhole conditions. The measurements have been obtained for the first time on two directional wells in the Gulf of Mexico. On the first well the sub was run in a rotary drilling assembly in the inclined section. On the second well the sub was run behind a steerable system on the build and tangent section of the well. The bending moment measurements gave a detailed description of the well trajectory each time a course correction was made; during jetting operations for the first well, and during oriented and rotary drilling using the steerable motor for the second well. Relatively high transverse acceleration levels were found to be associated with the doglegs of the wells, while relatively low axial acceleration levels were associated with drilling the soft shale formations. The transverse vibrations were shown, for the particular assemblies used, to vary almost linearly with rotary speed for the range studied. However, the transverse vibrations, as well as the bending moment were shown to be sensitive to downhole boundary conditions, especially in open hole sections. On each well measurements were made, at various flow rates, of the differential pressure across the components below the measurement sub; the bit for the first well, and a positive displacement motor plus the bit for the second well. From this data inferences could be drawn concerning pump efficiency and calibration of the downhole weight on bit measurement. In addition, measurement of the differential pressure can be seen as a potential aid in the identification of drillstring washouts, erosion or blocking of nozzles, and bearing wear in downhole motors.

Maximizing hole conservation while optimizing well economics in both conventional and deepwater wells is a continual challenge. Addressing these challenges with new technology has provided some significant solutions, but the uncertainty when utilizing new technology with no proven track record must be risk-weighted. Solid Expandable Tubulars (SETs) have been installed in both openhole and cased-hole wellbores from November of 1999, in a variety of environments in wells on land, offshore and in deepwater to solve a range of drilling and completion challenges. This paper will discuss the drilling case histories in depth including:Descriptions of drilling challenges surrounding the use of SETs and their next best alternativesRisk analysis leading to the use of SETsDiscussion of the advantages and disadvantages of using SETsOperational lessons learned during installations of SETs Technology Overview Previously published papers and articles have discussed the concepts of Solid Expandable Tubular technology1 and the effect of the expansion process on the system's tubulars2,3 and connectors4. In this paper, the basics of SET technology will be briefly reviewed, emphasizing how the early products of this new technology have been applied in the drilling environment. Presentation of several case histories will demonstrate that Solid Expandable Tubular products can provide additional tools for the drilling "tool box", ultimately cutting drilling costs and bringing more dollars to the bottom line. As of this writing, 15 jobs have been performed, of which three were unsuccessful. Since learnings often are the results of problems, heavy emphasis will be placed on problems and the lessons learned. The Expansion System. The underlying concept of expandable casing is cold-working steel tubulars to the required size downhole - a process that, by its nature, is very unstable mechanically. Thus, there are many technical and operational hurdles to overcome when using cold-drawing processes in a downhole environment. An expansion cone, or mandrel, is used to permanently mechanically deform the pipe (Fig. 1). The cone is moved, or propagated, through the tubular by a differential hydraulic pressure across the cone itself and/or by a direct mechanical pull or push force. The differential pressure is pumped through an inner-string connected to the cone, and the mechanical force is applied by either raising or lowering the inner-string (Fig. 2). The progress of the cone through the tubular deforms the steel beyond its elastic limit into the plastic region, while keeping stresses below ultimate yield (Fig. 3). Expansions greater than 20 percent, based on the inside diameter of the pipe, have been accomplished. However, most applications using 4–1/4 inch to 13–3/8 inch tubulars have required expansions less than 20 percent.

No e x t e n d e d a b s t r a c t wa s s u b mi t t e d i n s u p p o r t o f t h e t e c h n i c a l p r o g r a m p r e s e n t a t i o n d e s c r i b e d i n t h e a b s t r a c t .