Multi-criteria material selection for casing pipe in shale gas wells application

Abstract

The conventional method of casing selection is based on availability and/or order placement to manufacturers based on certain design specifications to meet the anticipated downhole conditions. This traditional approach is very much dependent on experience as well as constructing oil and gas wells at minimum budget. However, this material selection approach is very limited in meeting the requirement of shale gas wells. This study utilises the material performance indices and ANSYS Granta database to examine three different casing pipe buckling scenarios including the buckling with corrosion potentials and buckling with impact and long-term service temperature conditions. Consequently, numerical evaluations of the response of the selected casing materials established the stress, deformations, and safety factor for the first scenario (shale gas well with buckling tendencies). The significance of this new method is added advantage in terms of integrating materials’ physicochemical, thermal and mechanical properties and the casing functional performance to establish ideal selection within the design space or requirements. Results obtained in this study show that there are optional materials that outperform the most common casing grades (P110 and Q125) utilised in shale gas development in terms of both safety and cost. This study established a procedure for evaluating optimum performance between cost, safety, performance indices and materials’ physical and mechanical properties for a typical well design scenario. This procedure will assist the design engineer to justify the selection of a particular material(s) safely and technically for a given shale well casing application in future. In all the 10 materials investigated, even though the P110 (API casing grade) meets the buckling design scenario and widely used in shale gas well development, there are many alternative viable material candidate options that outperform P110 Grade with the best material candidate studied in this work being BS 145.