Terry H. McCoy

Expandable Tubular Solutions

Two 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.

SSC Resistance of QT-900 Coiled Tubing

Laboratory sulfide stress cracking (SSC) tests were performed on specimens taken from a QT-900 coiled-tubing test string in an attempt to define zones of acceptable sour service. SSC tests were performed at room temperature in brine fluid environments with H2S partial pressures (PH2S) ranging from 0.01 to 10 bars and pH levels from 2.8 to 4.5. In addition, the effectiveness of a new inhibitor for crack prevention was tested. SSC testing, which included NACE Method A tensile, four-point bent beam and slow strain rate test specimens, were performed on as-milled as well as fatigue-cycled tubing. Fatigue cycling of the QT-900 test string was performed on a pressure bending fatigue machine with tubing samples cycled from 33% to 75% of average tested fatigue life. Test specimens were taken from parent metal, bias weld, seam weld (ERW), and butt weld locations. As a result of this test program, acceptable zones of service in sour environments have been proposed although further testing may alter boundary locations.