As an enabling technology, solid expandable tubulars continue to revolutionize the design and construction of oil and gas wells. Although solid expandable systems are now widely accepted as a viable casing alternative, some operators do not apply the technology in their wells. Limited information regarding the tubulars' post-expansion performance properties creates uncertainty in the application of solid expandable tubulars. A better understanding of how the pipe properties are affected by the expansion process is imperative to optimizing the benefits of system application. Using American Petroleum Institute (API) performance equations on post-expanded tubulars do not clearly identify the limits of the pipe. Testing is underway to create accurate predictive models for expansion force and post-expansion collapse. These full-scale laboratory tests, using API methods where applicable, determine how the expansion process changes collapse resistance and residual stress. Pre and post expansion mechanical and material properties are analyzed using American Society for Testing and Materials (ASTM) methods. Testing for H2S and CO2 environments employ the NACE methods. This paper describes the testing procedures and results of the post-expansion performance property testing. These findings will be compared and contrasted to API standards for conventional pipe. In addition, the paper will discuss industry implications for determining solid expandable tubular standards. Introduction Solid expandable tubulars have an installation legacy that has provided a solution to save casing points and preserve hole size in drilling and workover operations alike. These enabling systems have successfully been incorporated into the original drilling design1, installed to mitigate unexpected troublesome formations, turned existing wells into big-bore producers2 and been seamlessly combined with other revolutionary technologies to address downhole challenges3,4. With wider use of solid expandable tubulars, interest in their performance properties has grown, particularly with respect to collapse resistance. Historically, collapse testing of expandable pipe has been limited. The tests that have been performed indicate that the collapse resistance of expanded pipe is closely approximated by the conventional API collapse equations. However, API collapse strength theory is empirically based. The equations do not consider the residual stress that may be present after expansion. In addition, the API equations are based on tests conducted many years ago. Manufacturing processes, tolerance control, and material performance have all improved since that time. The energy industry has a limited understanding of the post-expanded properties of solid expandable tubulars even with over 700 installations globally. Although the industry has a knowledgeable grasp on the application of OCTG in designing well applications, taking the same pipe and mechanically yielding it to a larger size is the source of operator skepticism. Questions raised include:How do the pipe properties change after expansion?Does any residual stress adversely affect pipe properties?Does the pipe work harden?Does the pipe have or still retain its resistance to H2S and CO2? The concern most commonly raised is the effect on collapse and H2S resistance. Some operators arbitrarily degrade expandable pipe collapse properties due to residual stress because of the lack of comprehensive data. Similarly, some operators will not use expandables in minor H2S environments for the same lack of confidence. Specific testing was recently conducted to address these concerns and provide the basis for solid expandable pipe standards. Testing methodology To develop confidence in the understanding of post-expansion pipe properties, a plan was initiated to investigate expanded pipe with a broad range of expansion ratios, across a range of pipe sizes from various manufacturers. Material properties were tested both pre-expansion and post-expansion to better study relationships between percent expansion and various performance parameters.
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