Development of an Optimized Tubular Material for Thermal Slotted Liner Completions

Abstract

Use of slotted liner as a sand control device is widespread in SAGD operations in Western Canada. Operating temperatures in such thermal EOR wells can be extreme, sometimes exceeding 270°C (518°F), and the associated compressive axial mechanical strain imposed by constrained thermal expansion can load the pipe material beyond its proportional limit. Selection of an appropriate slotted liner configuration is critical to ensure that structural stability (and hence sand control) is reliably maintained during operation. Mechanical properties of the tubular material at elevated temperature strongly influence the compressive stability of the liner structure, but lower-temperature properties also affect the ease of pipe slotting on a production scale, which is typically achieved by plunging thin saw blades through the pipe wall. Common slotting issues include breakage or unacceptably high blade wear rates. This paper describes the developmental basis for a new tubular material formulation that is specifically optimized for thermal structural stability in SAGD applications without compromising slotting performance. Elevated-temperature mechanical properties are designed to prevent compressive buckling failures and to minimize strain localization potential. Results of analytical and experimental work (including stability analysis of the liner structure, thermo-mechanical material testing, and bench-scale slotting trials) are described. Introduction Ongoing rapid development of bitumen reserves in Western Canada has led to an increased focus on developing robust tubular design bases for extreme service conditions in in-situ recovery schemes such as SAGD. Specifically, cemented or frictionally-constrained tubulars are subjected to thermally-induced, deformation-controlled loading that leads to a unique set of design challenges and more stringent requirements for post-yield material response than those employed in traditional elastic design. Slotted liner is used as a sand control device in a majority of SAGD wells. Slotted liners used in thermal applications must provide a stable structure under extreme thermally-induced compressive loading in order to maintain wellbore access and to prevent excessive sand from entering the wellbore. While the deformation resistance of slotted liners depends on geometric attributes such as pipe wall thickness, slotting configuration, and slot geometry, material properties have a considerable impact on structural stability and localization resistance.

Burst and Collapse Responses of Production Casing in Thermal Applications

“…In general, one can expect that increased post-yield stiffness (at field-representative conditions) will improve the deformation-tolerance of a particular tubular configuration. The same is not always true for yield strength, in which the increased strength can generate larger instability potential because it effectively increases the axial force carried by the structure; an example is thermal slotted liner (Dall'Acqua et al 2005, 2010. A small sensitivity study was executed to establish the impacts of both yield strength and post-yield stiffness on ovalization performance of thermal production casing.…”