API 17TR8 Research Articles

Technology Focus: High Pressure/High Temperature (March 2023)

The array of papers received for review this year covers a wide spectrum, both in applications and research, which indicates that the exploration and production (E&P) industry is actively working to monetize high-pressure/high-temperature (HP/HT) reservoirs. The pandemic has already put an indelible mark on the industry during the past 2 years. The present geopolitical scenario is posing a serious challenge to countries’ energy security. The oil and gas sector is confronted with the biggest task in society—addressing climate change. The E&P sector is going to face stiff challenges in the coming days, with the word “petroleum” being substituted by the word “energy” to cover wider possibilities. Eminent actions are distinctly visible in the strategic planning of fossil fuel companies and the capital-expenditure investments in the E&P sector. Companies are shifting priorities toward diversification, resilience, and decarbonization. Safety continues to dominate HP/HT operations and will do so in the future with more-stringent measures and compliances. Cost-effective technology solutions blanketing the entire domain of HP/HT activities will provide exploitation on a sustainable basis with collaboration between industry and academia. While reviewing the papers, every attempt was made to provide a fair representation that cuts across the HP/HT domain to show the reader what is happening in the industry, both in the field as well as in research, over different geographical locations. Several of these case studies presented inspiration tied to the indomitable human spirit that can overcome challenges through innovation. Recommended additional reading at OnePetro: www.onepetro.org. SPE 210702 An Integrated Approach in Pore-Pressure Prediction Contributes to Drilling Success of an HP/HT Wildcat Well in the South China Sea by Lijun Guan, CNOOC, et al. SPE 209865 Challenges of an HP/HT Completion Design With Extreme H2S and CO2 in a Carbonate Gas Development by C.W. Graham Grant, PTT Exploration and Production, et al. OTC 31051HP/HT Subsea Connector Verification and Validation Using an API 17TR8 Methodology by Barry Stewart, TechnipFMC, et al. SPE 210543 Bridging the Gap: Highly Depleted Reservoir Entry in a Mature HP/HT Field by Michael Cadd, Shell, et al. SPE 211735 Innovative Solutions to Subsurface Challenges in Deep Hard-Rock High-Temperature Slim Wells by Khalifa Omair Wahshi, Petroleum Development Oman, et al.

Cost-Effective Validation of HP/HT Subsea Equipment Using Seawater Hydrostatic Head

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper OTC 29413, “Validation of Cost-Effective Design Methods Using Hydrostatic Head for High-Pressure/High-Temperature Applications,” by Parth Pathak and Nicholas Katsounas, OneSubsea, prepared for the 2019 Offshore Technology Conference, Houston, 6–9 May. The paper has not been peer reviewed. Copyright 2019 Offshore Technology Conference. Reproduced by permission. Validation testing of subsea equipment designed for high pressure/high temperature (HP/HT) applications is necessary but can be extremely expensive and infeasible. The complete paper presents a practical approach for validating design-verification analysis for subsea equipment, using a representative pressure valve block to correlate finite-element analysis (FEA) predictions for strain changes with actual measured changes. The design methods use the guidelines in technical report API 17TR8, and load cases per API 17TR12. Introduction Current editions of API standards covered in API Subcommittee 17 (API SC 17) for subsea production equipment are geared toward designing the equipment for its absolute internal working pressures. Also, on the basis of previous regulatory requirements for the offshore industry, until 2014 it was not advised to take advantage of the external seawater hydrostatic head and other external pressures to design certain types of subsea equipment covered under API SC 17. Thus, equipment per its corresponding API standards was designed to have an absolute rated working pressure always greater than the well shut-in tubing pressures. Three API technical reports published in 2014 and regulatory guidelines for the Gulf of Mexico published in 2017–2018 provide design guidelines for depth-adjusting subsea equipment specific to its working seawater depths, and detailed verification and validation guidelines for designing HP/HT equipment—that is, with absolute internal pressure rating exceeding 15,000 psi and temperatures exceeding 350°F. These guidelines can be used to develop subsea equipment rated to working pressures greater than 15,000 psi. The complete paper details the step-by-step methodology of combining the API 17TR12 and API 17TR8 design verification guidelines to depth-adjust typical existing 15,000-psi-rated subsea equipment for HP/HT use. Validation tests for external pressures for entire equipment assemblies can quickly become impractical and infeasible for most of the equipment covered in API SC 17 because of the sizes and complexity of the equipment. The authors believe such testing is not entirely necessary because testing for external pressure of critical and representative components, which are pressure-containing and -controlling, can be sufficient to validate the applicability of the external pressures for the equipment. Furthermore, they contend that for larger components for which hyperbaric chamber testing might not be feasible, comprehensive FEA can be used to validate stresses and deflections as long as the FEA methods and results are appropriately validated. The complete paper presents the various tests that were performed covering typical subsea equipment and are deemed sufficient to validate the verification methods used to depth-adjust using external pressures. The actual tests performed were part of an HP/HT development for the completion and workover riser (CWOR) system for a potential application that required depth-adjusted working pressure higher than 15,000 psi. The work performed was to validate the design and verification of the equipment manufactured by the services provider and cannot be applied to other manufacturers or engineering houses.

Development of a Novel Test Method to Characterize Material Properties in Corrosive Environments for Subsea HPHT Design

Abstract High pressure high temperature (HPHT) design is a significant new challenge facing the subsea sector, particularly in the Gulf of Mexico. API 17TR8 provides HPHT Design Guidelines, specifically for subsea applications. Fatigue endurance (i.e., S–N) and fracture mechanics design are both permitted, depending on the criticality of the component. Both design approaches require material properties generated in corrosive environments, such as seawater with cathodic protection and/or sour production fluids. In particular, it is necessary to understand sensitivity to cyclic loading frequency (for both design approaches), crack growth rates (CGR) (for fracture mechanics approach) as well as fracture toughness performance. For many subsea components, the primary source of fatigue loading is associated with the start-up and subsequent shutdown operation of the well, with long hold periods in-between, during which static crack growth (CG) could occur. These are the two damage modes of most interest when performing a fracture mechanics based analysis. This paper presents the preliminary results of a novel single specimen test method that was developed to provide fatigue crack growth rate (FCGR) and fracture toughness data in corrosive environments, in a timeframe that is compatible with subsea HPHT development projects. Test data generated on alloy 625+ in seawater with cathodic protection are presented along with a description of how the test method was developed. A crack tip strain rate based formulation was applied to the data to rationalize the effect of frequency, stress intensity factor range (ΔK), and maximum stress intensity factor (Kmax).