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AbstractA laboratory program designed to determine the effects of tubular expansion and method of tubular expansion upon the mechanical properties and pipe performance of selected grades of carbon steels and martensitic stainless steels has been conducted.Well completion design that incorporates downhole tubular expansion, a relatively new technology, requires a complete understanding of the mechanical properties and performance of the expanded tubular. The dissemination of this knowledge is required for the informed use of this technology, which can permit access to hydrocarbons that cannot be reached by conventional drilling and completion schemes.Tubular expansion is a cold working process and alters the mechanical properties of the OCTG. Alloy system, expansion method, pipe loading conditions during expansion, and post expansion thermal treatments and its kinetics were studied. This laboratory study demonstrated that each shows pronounced effects on the final mechanical properties of the steel (i.e., its stress-strain behavior, yield, ductility, fracture toughness, and defect tolerance), residual stress in the OCTG, resistance to sulfide stress cracking, and performance of the expanded OCTG (e.g., collapse pressure).The results of this study can be used to plan a program of materials qualification of a steel as an expandable to assure that the pipe properties and performance are fit-for-service downhole after expansion. Further, the results of this study can be used to infer the mechanical properties and performance of expanded tubular products for downhole use, e.g., for collapse.
OTC 17622were seamless. One of the martensitic stainless steels was a laser seam welded pipe; the others were seamless.In most cases the compositions and mechanical properties of the as-received (unexpanded) pipes were determined as a cross check with the mill certificates. The compositions, and mechanical properties and dimensions of the as-received versions of each of these are listed in Tables 2 through 4.
Expansion Techniques.General Study: In each case, pipe was expanded by a single, solid, tapered cone with a mandrel for guidance and centralization ahead of the cone. The cone material was a high strength tool steel that was either AISI D2 or AISI D3 (UNS T30402 or UNS T30403, respectively) and heat treated to produce a hardness of HRC 58-62 for wear resistance.
Cone Expansion as a Function of Pipe Loading and Method.In one study, samples of a 50 grade, Q&T, seamless carbon steel pipe were expanded by 15% (based upon the change in the inside diameter) with each pipe specimen subjected to one of five different loading conditions. The pipe specimens were from the same heat treat lot of this steel. The pipe was 7-5/8 inch O.D. x 0.375 inch wall. These expansions were performed at our facility with the pipe specimen in the horizontal position.This study was conducted to determine the effect of loading condition on the steel's post-expanded mechanical properties and the pipe's dimensions...