Subsea Industry Research Articles

Multicore-fiber submarine systems [Invited

This paper reviews and analyzes multicore-fiber technologies in the context of submarine networks. As global/transcontinental capacity continues to grow at a large and steady pace, the subsea industry is challenged to deliver technologies that provide large-capacity networks in a faster, greener, and cost-effective fashion. Multicore fiber has been considered as a serious candidate for next-generation systems with the ability to maintain standard cable size at large core counts. This paper analyzes the technoeconomics of next-generation submarine systems including variables such as equipment size versus marine cost and other critical elements (not analyzed before, to our knowledge) for submarine system implementation. In this context, this paper also analyzes the state-of-the-art of multicore subsystems and components and discusses their roadmaps, requirements, and evolution toward the realization of a multicore ecosystem for next-generation SDM systems.

Technology Focus: Subsea Systems (August 2023)

Emerging from the COVID-19 pandemic, and coupled with increasing activity for energy production, the latest focus on subsea systems indicates that the subsea industry is moving with the times, reflecting technology developments, and meeting overall society demands in terms of holistic energy supply. The papers reviewed and selected focus on key development areas—carbon capture, utilization, and storage (CCUS); renewable energy applications; and subsea storage. Implementing subsea systems to meet energy demands maintains the traditional emphasis on reviewing, refining, and incrementally improving the techniques and technology applications of today. Such efforts have a huge bearing on the direction of subsea engineering, and the overall efficiency and effectiveness of subsea operations cannot be underestimated in their contribution to the energy mix. It is worth noting that, with the current focus on greenhouse gas (GHG) emissions, subsea developments are among the lowest in terms of GHG footprint per barrel of oil equivalent, reflective of application improvements over many decades. While not a solution to the overall energy challenges themselves, this is a good marker for where future offshore industry efforts are positioned with regard to the energy transition. Specifically looking at the papers in review, we see carbon storage optimizing subsea development potential, adding to and incorporating existing technology as well as adapting it to optimize the massive potential of subsea CCUS storage, particularly in conjunction with near-shore CO2-production-intensive industries. In addition, with a nod toward the energy transition, the application of renewable energy to assist with reducing the GHG footprint of subsea operations is presented. Finally, from an efficiency point of view, as existing subsea systems approach all-electric operations, the parallel demand for increasing monitoring through improved sensing and communications is presented through analysis of all-optical subsea sensing capability with a potential effect on life-of-field efficiency. I hope these selections will spur thoughts and affect how we as subsea engineers approach future developments for both hydrocarbon and energy-transition requirements. Recommended additional reading at OnePetro: www.onepetro.org. SPE 210910 Innovative Industry Lead Project for Renewables for Subsea Power by Ian Roger Crossland, Mocean Energy, et al. SPE 205433 A Road Map for Renewable Energy Integration With Subsea Processing Systems by Juliano Pimentel, Aker Solutions, et al. OTC 31294 Subsea Liquid Energy Storage—The Bridge Between Oil and Energy/Hydrogen by Kristian Mikalsen, National Oilwell Varco OTC 32449 A New Subsea Station for Deep Gas Treatment Allowing Maximizationof Subsea Gas Fields Production by Paul Roland, Saipem, et al.

Exploring exploration—how to look for deep-sea minerals

AbstractIn the spring of 2023, the subsea industry in Norway is gearing up for an opening of the Norwegian continental shelf (NCS) for deep-sea mineral exploration and extraction. Existing research indicates that the profitability of deep-sea mining with today's technology heavily depends on high ore grades. This study explores the potential for emerging techno-operational concepts for exploration to affect the profitability of seafloor massive sulfide (SMS) industry on the NCS. By way of computer simulation, the study analyzes technologies currently or soon poised to enter the subsea market concerning their advantage or disadvantage for the SMS industry on the NCS. The study indicates a significant advantage in developing geophysical sampling technology for assessing mineral resources and some advantage in developing unmanned surface vessels for regional surveys. It further indicates that developing fleet-operated autonomous underwater vehicle concepts for high-resolution surveys is not only moot but possibly counterproductive. The study thereby contributes techno-operational insight for a budding industry currently looking for technology to improve commercial prospects.

Sensor design for saltwater ingress detection in high reliable all-electric deep sea actuators

Subsea oil and gas production relies on Xmas Trees which are mounted on boreholes. Xmas Trees are an arrangement of different valve types and sizes actuated by hydraulic, electro-mechanic or all-electric actuators. All these actuators sharing problems with saltwater ingress and the re-sulting increased wear. This paper investigates potential effects which can be measured after saltwater ingress. Extensive testing is executed and the investigated effects are used for novel sensor designs. These designs are evaluated regarding certain requirements and a resulting sen-sor design is proposed for industrialization. The resulting sensor can then be used to collect new important data to support optimal maintenance in the subsea industry.

Optimization of Centrifugal Pump Impeller for Pumping Viscous Fluids Using Direct Design Optimization Technique

Pumping viscous fluids using centrifugal pumps in the subsea industry is very common. The pump performance degrades drastically when the viscosity of fluids increases, which ultimately gives rise to the installation and oil production cost. Their design optimization can lead to a significant improvement in their performance. Therefore, this study presented the effect of impeller geometry on pumping fluid viscosity through impeller design optimization. Here, pump operation is simulated numerically by solving the Reynolds-averaged Navier-Stokes (RANS) equations at different flowrates. Experimental testing is also performed using the same oils, for numerical validation. Artificial neural-network-assisted multiobjective optimization was performed with two independent design parameters; wrap angle and splitter blade length of impeller, with head and input power as objective functions. Wrap angle and splitter blade length, both significantly affect pump performance while pumping viscous oils; as the oil viscosity increases, increasing splitter length and decreasing wrap angle improve the head significantly.

High data rate ultrasonic communications

Ultrasonic signals have been used in biomedical applications since at least the 1940s. Underwater acoustic signals have been used in the subsea industry for ranging since the early 1900s and for SONAR imaging and communication in the decades that followed. Since the development of subsea communication systems in the 1940s, increasingly sophisticated means have be developed for transmitting information acoustically through the highly variable ocean environment. State-of-the-art acoustic communication systems leverage ultrasonic transducers to achieve data transmission rates that mirror radio-frequency (RF)-based WiFi systems on land. The increasing use of wireless implanted medical devices (IMDs) have increased interest in through-tissue communications. Restrictions on the available bandwidth and transmit signal power limit the data rates of RF-based IMDs. In this talk, we give an overview of video-capable ultrasonic wireless communication between IMDs and external devices. We emphasize the potential of such a system for improving video capsule endoscopy and describe the challenges of through-tissue acoustic communication. Building on experience with subsea-communication systems, we discuss methods to cope with attenuation, dispersion, reflection, and nonlinear propagation. Some of our recent experiments performed ex vivo with soft tissue samples and in vivo with anesthetized animal subjects will be discussed.

Resilience assessment of a subsea pipeline using dynamic Bayesian network

Microbiologically influenced corrosion (MIC) is a serious concern and plays a significant role in the marine and subsea industry’s infrastructure failure. A probabilistic methodology is introduced in the present study to assess the subsea system’s resilience under MIC. Conventionally, the risk-based models are constructed using the system’s characteristic features. This helps decision-makers understand how a system operates and how the failed system can be recovered. The subsea system needs to be designed with sufficient resilience to maintain the performance under the time-varying interdependent stochastic conditions. This paper presents the dynamic Bayesian network-based approach to model the subsea system’s resilience as a function of time. An industry-based application study of the subsea pipeline is studied to demonstrate the efficiency and effectiveness of the proposed methodology for the resilience assessment. The proposed methodology will assist decision-makers in considering the resilience in the system design and operation.

Transferring Needs and Operational Experience from Life‐of‐Field to Engineering functions ‐ a case study from the Subsea Industry

AbstractThis paper investigates how a company in the subsea industry are transferring needs and operational experience from Life‐of‐Fields functions to Engineering functions, to allow for more holistic life cycle design and to improve engineering solutions. The subsea industry is changing, putting more emphasis on total life‐cycle cost. In order to improve their offerings, suppliers within this industry see the need for more effective utilisation of Life‐of‐Field's needs and operational experience. Challenging communication between Life‐of‐field and Engineering affect transference of needs and operational experience, hindering engineering for life cycle. To research this problem, we investigated the operational process and made in‐depth interviews of relevant personnel at both the Engineering and Life‐of‐field functions of a global subsea supplier. We discovered that suboptimal transference of needs and operational experience between the Life‐of‐Field and Engineering functions results in added work, repetitive design issues and operational inefficiencies from project to project. We found an insufficient organisational process, low prioritisation of cross‐functional feedback together with formal tools not fit for purpose to be the predominant causes for ineffective transferring of needs and operational experience between Life‐of‐Field and the other functions. Suggestions for improving the transference of needs and operational experience are presented based on the findings and analysis.

One or all channels for knowledge exchange in clusters? Collaboration, monitoring and recruitment networks in the subsea industry in Rogaland, Norway

ABSTRACT Existing research has emphasised various mechanisms for knowledge exchange in industry clusters, including inter-firm collaboration, labour mobility, and monitoring of other firms. However, these mechanisms are normally studied in isolation, and we know little about how they interrelate. This paper examines which firms collaborate within a cluster. We ask whether knowledge exchanges through other channels, specifically monitoring and labour mobility, are positively or negatively associated with collaboration. We use data from interviews with 30 firms in the subsea sector in Rogaland, Norway, representing nearly the entire population of the cluster, to examine the association between the different forms of linkages. The results from Social Network Analysis reveal an overall high degree of knowledge exchange among the organisations making up the subsea cluster. Furthermore, using Quadratic Assignment Procedure (QAP) regression analysis, we find that collaborative linkages are significantly more likely to exist between firms which share recruitment and/or monitoring linkages.

Enhancement of Corrosion Resistance of Aluminum 7075 Surface through Oil Impregnation for Subsea Application

This study investigated the corrosion resistance of oil impregnated anodic aluminum oxide (AAO) surfaces of aluminum 7075 for subsea application. Although aluminum 7075 has high strength, it is scarcely used in the subsea industry because of its corrosion issue. Some treatment of aluminum 7075 is required for subsea application. In this study not only a plate shape but also a cylindrical shape were investigated because a cylindrical shape is frequently used in the subsea industry for electronic device housing. Contact angles of bare aluminum and oil impregnated AAO surfaces of aluminum 7075 were measured after a salt spray test and a pressure test. The results showed that the contact angle of bare aluminum was considerably decreased after the salt spray test, whereas the oil impregnated AAO surface presented a relatively high contact angle after the salt spray test and the pressure test. These results showed that the corrosion resistance of aluminum 7075 could be enhanced by oil impregnation on the AAO surface, and thus can be utilized in the subsea industry.

A review on subsea process and valve technology

The world’s energy consumption continues to increase steadily. Fossil fuels (oil, natural gas, and coal) still comprise more than approximately 85% of the world’s energy consumption. Offshore oil field development and operation began by using platforms and ships, but oil producers and operators are looking for new and innovative ways to reduce production costs and improve recovery and production rates from reservoirs. As a result, subsea production solutions are becoming more popular. A subsea production system consists of subsea completed well(s), seabed wellhead(s), production tree(s), subsea tie-ins to flow line systems, and subsea equipment and control facilities to operate the well(s). The wellhead consists of the pressure-containing components at the surface of an oil and gas well that provide the interface for drilling, completion, and testing of the well, in addition to production equipment. Subsea manifolds are used to simplify the subsea system, minimizing the usage of subsea pipeline and risers while optimizing the fluid flow. Subsea valves, which are mainly ball or through conduit gate valves, are located on the trees and wellheads and designed based on API and ISO standards. They are made in exotic corrosion-resistant alloys to avoid different types of corrosion such as hydrogen-induced stress cracking, and should withstand high-pressure classes. These valves can be manual or actuator-operated with or without the help of a remote-operated vehicle. The subsea industry is shifting from hydraulic-type to electrical-type actuators for important reasons including reduced costs and faster operation. Newly designed subsea valves should pass strict qualification tests such as hyperbaric tests, endurance tests, and pressure and temperature cycle tests.

Extra-Long Subsea Tiebacks Reduce Deepwater Development Costs

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper OTC 28839, “Deepwater Innovations: Extra-Long Oil-Tieback Technologies,” by Michael Gassert, Gianluca De Molli, Vito Calabrese, Eniprogetti, and Stefano Magi, Gianfederico Citi, and Fabrizio Rollo, Eni, prepared for the 2018 Offshore Technology Conference, Houston, 30 April–3 May. The paper has not been peer reviewed. Copyright 2018 Offshore Technology Conference. Reproduced by permission. It now appears possible to reduce deepwater development costs by increasing the distance between new assets and existing production hubs and shallow-water areas, or even connecting those assets to shore. The•complete paper presents and discusses the authors’ technology-development program regarding very-long oil-tieback architectures (50–100 km) and enabling technologies. The paper describes how the new technological solutions compare with more-conventional development schemes in concept-selection phases and discusses how the operator is preparing for potential implementation. The authors believe that the capacity to invest in and develop technologies required for long•and very-long tiebacks will decide the future of the deepwater subsea industry. Introduction Over the past few years, Eni and its partners installed more than 100 subsea trees, mainly on deepwater fields in various areas of the globe, in particular Angola, Norway, Indonesia, Ghana, Egypt, and Libya. The growing trend in subsea trees is guiding the operator’s needs and ideas about how to develop fields progressively around its production hubs. In the evolution of deepwater oil fields, production floaters have been located close above the first fields to be developed. To guarantee the progressive infilling of the production hub, a first series of tiebacks was developed for a range of up to 15 km from the hub. The second series of tiebacks, ranging from 25–30 km from the hubs, is under development. Architectures and technologies to develop these tiebacks have been extensively studied, matured, and optimized, and some of those tiebacks are already in production. New infilling fields are currently being explored and discovered at distances 30 to 100 km from production hubs, with new extra-long tieback architectures now under study. Those tiebacks will necessitate new technologies to enable managing the growing technical and economic challenges of subsea field developments. Long and very-long tiebacks that allow expanding from a brownfield perspective are likely to enable today’s greenfield programs.• The paper reviews architectures and operation features of the operator’s currently installed short- and medium-length tiebacks to introduce the drivers and features of very-long tiebacks. The paper addresses sizing, operation targets, flow assurance, technologies, and related maturity. Short- and Medium-Length Tieback Review The operator’s initial deepwater fields have been developed with the production hub typically a few kilometers from the first main reservoirs in the direction of shallower water depth, allowing minimum distances dictated by drilling and offloading requirements. The main field is connected to the hub through a conventional wet insulated loop, which collects production from all the field’s drilling centers. Flowline diameters have usually been in the range of 10–12 in.

Underwater Robots: From Remotely Operated Vehicles to Intervention-Autonomous Underwater Vehicles

Remotely operated vehicles (ROVs) revolutionized the subsea industry when they were introduced in the 1960s. They were more powerful and inherently safer, and they could go deeper than divers. However, they require a tether and a support ship, which makes their use complex and expensive. Autonomous marine vehicles (AMVs) have long been seen as a game changer in the exploration and exploitation of the marine environment. Repeated access to remote and hazardous places for data gathering and intervention, enabled by their autonomy, is the key to their adoption. While historically the focus has been on autonomous underwater vehicles (AUVs), unmanned surface vehicles (USVs) have recently been developed and adopted at an increasing rate. Interestingly, whereas AMVs (AUVs and USVs) have now been adopted in niche areas (bathymetric surveys and mine countermeasures), they have not yet hit the mainstream. In this article, we review the state of the art in unmanned underwater vehicles (UUVs), which include ROVs and AUVs; current obstacles to their adoption, both technical and commercial; and recent advances in technology. We also present an outlook on the future of these systems.

Spatial and Temporal Autocalibration for Underwater Vehicles

The subsea industry is pushing for inspection and intervention vehicles with a high degree of autonomy which can ”live” and operate in connection with subsea facilities. Safety is often a major concern and high-quality calibration is essential for safe navigation with autonomous vehicles. This is because calibration quality is directly tied to the state estimation performance and thus the precision of navigation for autonomous vehicles. This paper presents an algorithm for calibrating the relative pose and time delay between sensors on a robotic vehicle using batch optimization on recorded real-world sensor data.

Subsea-Fiber Wet-Mate Connectors Require Careful Design To Balance Cost, Performance

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 27987, “Subsea-Fiber Wet-Mate Connectors: Achieving the Balance Between Consistent Optical Performance, Product Cost, and Compact Size,” by Elaine Saxton and Helyson Parente, SPE, Siemens Subsea, prepared for the 2017 Offshore Technology Conference Brasil, Rio de Janeiro, 24–26 October. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission. As the hunger for data grows, long stepouts become more common, and fiber communication becomes standard, the use of fiber in subsea oil and gas fields is set to increase. While optical loss along fiber itself is low and data-collection possibilities are high, these applications will only be fully realized if wet-mate fiber connectors can achieve high optical performance consistently. Excellent results are achieved with compact design, a modular approach, and an emphasis on cleanliness. Introduction Wet-mate fiber connectors have been on the market for years and are used increasingly in the subsea oil and gas industry. While they have been moderately successful, the technical challenges should not be underestimated. Industry specifications demand high levels of optical performance and extensive qualification programs. The balance between performance and cost of the finished product has always been difficult to achieve. Subsea fields are seeing longer stepouts, which are suited to using fiber as the key communication network. Furthermore, the subsea industry is seeing an ongoing drive to use fiber sensors in downhole systems (e.g., distributed temperature sensing), allowing greater amounts of data to be transmitted topside. Other applications such as direct-current and fiber-optic distribution and pipe-in-pipe heating are also emerging. For reasons of flexibility and practicality, the wet-mate fiber connector plays an important role in all of these. Technical Challenges The key technical challenges are a mixture of mechanical design, operation and maintenance, and operational environment. Mechanical Design. The core of a standard single-mode fiber is 9 µm, and it must be completely aligned in every dimension for optical performance to be achieved. Manufacturing, Operation, and Maintenance. Cleanliness of the optical ferrule faces on every single mate is crucial. Without it, performance is degraded or lost. In the worst case, permanent damage is transferred by a dirty ferrule face mating with a clean one. Operational Environment. A wet-mate connector is a sealed, oil-filled, pressure-balanced mechanical device that will be handled in harsh topside conditions in extreme temperatures before being deployed to sea depths of up to 4,000 m. Operation and Maintenance. High optical performance is required on all lines for up to 1,000 mates. Subsea connectors typically are mated only a few times in deployment and lifetime operation, but the same connectors are used for testing topside where they see many more mates. Compact Size. Space on subsea equipment structures is always at a premium, and designs always need to be as efficient with space as possible.

Implementation of A3 architectural overviews in Lean Product Development Teams; A case study in the Subsea Industry

AbstractThis paper presents a case study investigating the use of A3 Architectural Overviews (A3AOs) in lean product development teams. A3AOs is a tool used in product development and lean manufacturing to increase communication and knowledge sharing across the organization. We studied the implementation in an engineering department of a global oil and gas supplier, by performing a case study and extensive depth interviews. We also studied earlier implementation initiatives of A3s in a thorough literature review. A finding was that, although current and former research have shown clear benefits of utilizing this tool, the company rarely uses it today. We wanted to investigate challenges with creating and implementing A3AO in the organization. Our results show that A3AOs may be a well‐suited tool to improve the requirements handover process within the company. We also make an outline of challenges and benefits with using and implementing A3AOs in the researched engineering department, with the goal to successfully implement A3AOs in the future.

All-Electric Subsea Well Brings Benefits vs. Traditional Hydraulic Technology

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper OTC 27701, “World-First All-Electric Subsea Well,” by Thomas Schwerdtfeger, Total E&P Netherlands; Bruce Scott, Halliburton; and Jan van den Akker, SPE, OneSubsea, a Schlumberger Company, prepared for the 2017 Offshore Technology Conference, Houston, 1–4 May. The paper has not been peer reviewed. Copyright 2017 Offshore Technology Conference. Reproduced by permission. Currently, the state of the art for subsea well control is based on hydraulic technology. Hydraulic fluid is supplied from a host facility to the subsea wells through dedicated tubes within an umbilical and is distributed to the wells. Shifting that trend, K5F3, the world’s first all-electric well in the subsea industry, opened to production on 4 August 2016. This paper presents the benefits of electric subsea control compared with current state-of-the-art hydraulic methods. Rationale for Electric Production System Expenditure Savings. When looking at the introduction of a new technology such as an electric system, successful introduction is a direct consequence of a perceived reduction in capital expenditure (CAPEX) and factors such as operating expenditure (OPEX); health, safety, and environment (HSE); and future readiness also need to be addressed. To perform preliminary system engineering for the implementation of the electric system and provide a comparison with a conventional electrohydraulic multiplex system, a case with five oil-production wells, one gas-injection well, and three water-injection wells was used as a base case for cost. The study concludes that the electric system is likely to show a range of benefits over the equivalent electrohydraulic multiplex system. Improved System Efficiency. Electric subsea production brings advantages in most scenarios, particularly in an ultradeepwater field or with long-distance step outs. Electric motors maintain their high level of efficiency and full torque capability regardless of water depth, unlike hydraulic pressure, which must over-come seawater hydrostatic pressure. Use of high-voltage direct current for long-distance power transmission is far more efficient than use of either alternating current or hydraulic pressure. Removing hydraulic tubing from the umbilical and reducing the number of conductors bring several advantages. The electric umbilical has a smaller cross section, allowing longer continuous lengths to be manufactured and spooled. Overall weight is reduced, facilitating the use of a smaller installation vessel. And, on very long stepouts, splices in the umbilical can be either reduced or eliminated altogether. HSE Improvement. An all-electric system eliminates the discharge of hydraulic fluid to the environment and hydraulic-pressure safety issues. Future Potential and Readiness. Having much higher levels of electric power available at the subsea end of the system (compared with the electrohydraulic system) offers a greater scope for powering additional tools and sensors such as multiphase flowmeters. It also facilitates the addition of intelligent wells, new sensors, and digital flow-control valves.

Electrification of Subsea Systems Requirements and Challenges in Power Distribution and Conversion

The subsea industry has become more predominant in recent years because of the discovery of a significant number of new oil and gas fields located in deep water, a term often used to describe offshore projects located in water depths greater than 600 feet. In order to extract oil and gas, a large number of electrical systems need to be deployed at the seabed. Many of these electrical systems need high-reliability power grid and power control units located on the seabed to minimize downtime. Power system and power electronics play a major role in providing the required and reliable power to various electrical systems. But there are many challenges for deploying power components under the seabed. This paper presents the challenges and the requirements of power system components operating in subsea environment, use of power electronics for efficient transmission of power from the offshore platform or from the shore to the subsea electrical loads; variable speed drive systems; and research areas related to power electronics for subsea electrical systems.

Numerical and Experimental Investigation of the Hydrostatic Performance of Fibre Reinforced Tubes

The increasing demands in subsea industry such as oil and gas, led to a rapidly growing need for the use of advanced, high performance, lightweight materials such as composite materials. E-glass fibre laminated pre-preg, filament wound and braided tubes were tested to destruction under hydrostatic external pressure in order to study their buckling and crushing behaviour. Different fibre architectures and wind angles were tested at a range of wall thicknesses highlighting the advantage that hoop reinforcement offers. The experimental results were compared with theoretical predictions obtained from classic laminate theory and finite element analysis (ABAQUS) based on the principal that the predominant failure mode was buckling. SEM analysis was further performed to investigate the resulting failure mechanisms, indicating that the failure mechanisms can be more complex with a variety of observed modes taking place such as fibre fracture, delamination and fibre-matrix interface failure.

Fatigue analysis of low alloy steel forgings used in the subsea industry

Design S–N curves are presented for low alloy machined steel forgings. Separate S–N curves are given for air and for seawater with cathodic protection. The selection of the S–N curve is made based on the tensile strength and the surface roughness. S–N curves for four tensile strength classes and two surface roughness classes are given. The tensile strength classes cover steels with a tensile strength in the range of 517–793MPa. The two surface roughness classes cover surface roughnesses up to Ra=6.3μm. Separate S–N curves are given for a stress ratio of R=0 and for a high mean tensile stress. Secondly, a method for adjusting the peak stress in the notch root with respect to the stress gradient is presented. The stress gradient corrected peak stress is used with the presented S–N curves for estimating the fatigue life of fatigue tested notched specimens with typical subsea design features. All estimated fatigue lives are demonstrably conservative compared to the test results for the wide variety of notched specimens types considered.