API 17TR8 – HPHT Design Guideline for Subsea Equipment – A Focus on Fatigue

Abstract

Abstract API Technical Report 17TR8: High Pressure – High Temperature (HPHT) Design Guidelines (API 17TR8) contains detailed guidelines on design methodology, material property requirements, design validation testing of pressure-containing and pressure-controlling components along with special requirements for seals and fasteners when considering the effects of HPHT retained (wellbore) fluids passing through subsea equipment (HPHT defined here as internally operating above 15 000 psi (103.5 MPa) rated working pressure and/or 350°F (177°C) operating temperature). It has gone through two revisions since its inception in 2012, updating its contents as HPHT knowledge and experience in the upstream oil and gas industry has been accumulated. The 3rd edition focused on improvements to material characterization protocols and clarifying wording in its use as a design guideline. This paper focuses on the 3rd edition's update to fatigue screening/analysis to establish design methodology and material functional specifications for subsea equipment used in oil and gas applications. Observed issues and concerns around fatigue screening, when and where to use it, use of S-N vs. Fracture Mechanics, and updates to material characterization for different environments, and fatigue curve modification are discussed.