Making Non-Metallic Downhole Tubulars a Reality – An Analytical Load Estimation Workflow

Abstract Non-metallic composite downhole tubulars provide significant value including less carbon footprint and reduced total cost of ownership. However, matching pipe performance envelopes to combined loading in different scenarios cannot be performed using commercially available software, due to various challenges including anisotropic pipe behavior, variation of material properties across the depth and change of well conditions. This publication highlights multidisciplinary collaborative efforts to estimate such loading in composite tubulars and compare to existing use cases. Load cases and conditions were determined, and analytical calculation workflows were deduced for loads at various depths and conditions across the lifetime. Load cases and alternate loading sequences are listed, interactions between tubular & system components are reflected and proper boundary conditions are applied to estimate such combined loads. Validation was performed against finite element analysis methods and methodology was applied in specific well applications. Results using suggested analytical methodology show good matching with numerical results using finite element analysis. Loads were matched against pipe performance envelopes with suggested safety margins for different pipe designs. Whilst pipe design changes, variation of pipe effective properties, including stiffness, density, and dimensions, affect the total combined loads acting on the tubular system. Well construction parameters including deviation profile, depth, and geothermal gradient affect conditions inside the well, differential pressure and axial loads. Change of system components including pipe connections, completion, installation tools and ancillaries significantly affects such loading profiles. These system components can be optimized and custom components and installation procedures for non-metallic composite tubulars can be developed and qualified to reduce such loads on the pipe. Application of reel-deployed thermoplastic composite pipes is unique and novel in downhole applications and must be accompanied by customized design workflows and validation programs. A new analytical design approach was developed for estimating the thermoplastic composite pipe structural response. This publication is bringing an integrated workflow for estimating these loads on non-metallic downhole tubulars, which – to the best of the authors’ knowledge – has not been presented elsewhere.