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 alternatives
Risk analysis leading to the use of SETs
Discussion of the advantages and disadvantages of using SETs
Operational lessons learned during installations of SETs
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 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.