Committee V.8: Subsea Technology
Authors: Horn Agnes Marie , Rahman Tauhid , Pasqualino Ilson , Duan Menglan , Kang Zhuang , Andersen Michael Rye , Konno Yoshihiro , Shim Chunsik , Teixeira Angelo , Oterkus Selda , Thornton Blair , Mishra Brajendra 
Published: April 2023

Committee Mandate
Mandate: Concern for the safety and structural reliability of subsea production systems for oil and gas offshore. This shall include subsea equipment for production and processing, flowlines and risers, with emphasis on design, fabrication, qualification, installation, inspection, maintenance, repair, life extension and decommissioning. Structural design for flow assurance and safe underwater operations shall be considered.

Introduction
The offshore and subsea industry is getting more complex with higher pressures, higher temperatures and increased water depths. Technology developments and impacts for the subsea industry are driven both by economic factors and by sustainability issues. These factors will enhance for novel subsea concepts like all-electric, new subsea processing technologies, further integration between process control and process safety systems and use of sensors to monitor process condition and integrity of safety systems. This report focuses mainly on the traditional subsea technology related to oil and gas fields where the attention will be on efficiency, safety, environment, digitalization and life extension.
This is the second term of the Specialist Committee V.8 Subsea Technology and as the previous report provided a more introductory outline to subsea technology, the following report will focus more in depth on the main trends seen by the industry like autonomous operations and operational challenges to accommodate for higher pressures, temperatures and ultradeep waters. Hence, areas like installation of subsea equipment have only been briefly discussed and operation for emergencies has been left out since this was thoroughly addressed by the previous committee.
The next level from electrification is to further explore the concept of subsea power distribution with the goal to provide power, ranging from 750 kW to more than 11 MW, to subsea systems, from pumps to compressors. All the major subsea players like GE Oil & Gas, ABB, TechnipFMC, Aker Subsea and Baker Hughes, are developing different concepts which are further discussed in Chapter 2. Another trend is the need for higher pressure and higher temperature (HPHT) and often in combination with ultradeep waters. One of the fields that have taken the new specifications for HPHT equipment is the 2,000psi rated subsea hydraulic junction plates including connection hardware for deployment at Chevron's Anchor development in the U.S. Gulf of Mexico just put in order. Hence, focus on safe design and new and updated design standards are presented in chapter 3. The demanding subsea environments challenge the boundaries of traditional engineering alloys and our understanding of degradation mechanisms that could lead to failure, new materials and fabrication of these have been discussed in chapter 4.
Carbon capture and storage (CCS) has been identified as a key abatement technology for achieving a significant reduction in CO2 emissions to the atmosphere where pipelines are likely to be the primary means of transporting CO2 from point-of-capture to sites. There is currently a strong interest to explore the use of pipelines for hydrogen transport, hence new pipeline trends and design assessment like strain based and leak limit states are discussed in chapter 5.
For the subsea industry, one of the main drivers is to put power on the seabed where subsea facilities are becoming all-electric. This technology will ensure huge capital cost savings for field developments and reduction in CO2 emission will become important. Chapter 6 deals with different riser concepts from traditional steel catenary, top tension and flexible risers to novel concepts like Thermoplastic Composite Pipe (TCP) and Carbon-Fibre-Reinforced Polymer (CFRP) risers and umbilicals.
The Macondo accident was an eye opener for the whole industry, and the Petroleum Safety Authorities of various countries challenged the industry on different levels to mitigate above associated risks and implement barrier management at the design stage. One of the challenges is the increased focus on design of subsea production system for oil and gas offshore in terms of safety and structural reliability of the system and its inherent management. Chapter 7 deals with structural integrity management, including inspection methods and advances in repair systems. The subsea industry faces a combination of market forces from authority, strict regulation and societal pressure over climate change, chapter 8 addresses structural reliability assessment and safety of subsea systems. Several of the offshore fields are approaching the end of their design life and a cost-effective solution to maximize production is to document that life extension is feasible for an asset, different solutions are discussed in chapter 9 including decommissioning.