The quality and reliability of oil casings play a pivotal role in the safety and efficiency of offshore oil and gas exploration. This study conducted research on resonant bending fatigue of 9-5/8-inch casing joints and established a systematic theoretical model for resonant bending fatigue based on the Euler–Bernoulli beam equation. The relationships between parameters affected by frequency and mode shape functions were deduced and solved to analyze the influence of wall thicknesses, length and weights at both ends of the specimen on the natural frequency of the resonant bending fatigue system. A full-scale fatigue test was then designed and conducted to investigate the circumferential stress distribution, reveal the stress amplitude–frequency response characteristics of the specimen, and explore resonance response behaviors under different excitation forces. This was done to establish a method for evaluating the oil casing life and obtain fatigue life characteristic curves of the specimen. A finite element model was employed to analyze the internal stress distribution of the coupling under bending moment load, considering the influence of material properties, thread lead angle and non-linear contact on casing joints. Finally, the fatigue life algorithm was summarized and compared by integrating the stress simulation results with the material properties of the specimen, elucidating the fatigue damage evolution process of casing joints. This research provides a significant engineering reference value for structural design optimization, fatigue testing and life analysis of oil casing threaded joints.

Abstract This paper provides an overview of a Geothermal Assessment Project (GAP) completed to assess the geothermal energy resource in and around an operational HPHT field on the UKCS. It demonstrates a new methodology to identify, assess and determine the amount of electrical power that might be realised from the geothermal resource and associated field infrastructure, and investigates both existing and future opportunities. Geothermal energy adoption into oil and gas net-zero portfolios remains relatively unexplored. This paper shares the results of the design and implementation of a novel integrated workflow to assess and evaluate the geothermal energy potential of producing offshore oil and gas assets from subsurface, wells, and topsides perspectives. The workflow is designed to allow operators to determine potential electrical power production from geothermal sources within existing field infrastructure alongside a model of the opportunity it provides to reduce CO2 emissions. Three geothermal production scenarios are defined, that are: proven co-produced fluid reserves, contingent co-produced and enhanced fluid resources and prospective exploratory geothermal resources. Existing and sanctioned production forecasts were used along with reservoir modelling to examine aquifer behavior and the ability for enhanced and sustained water production. Screening and complexity matrices were applied to identify and rank relevant reservoir plays and candidate wells. Process flow diagrams were interrogated to establish potential tie-in points for heat to power equipment and equipment characteristics required for enhancing heat to power generation were considered. The overall opportunity was also risk assessed from a flow assurance perspective. Results of the study are discussed in terms of the challenges and opportunities that exist to co-produce geothermal energy within the constraints of an established oil and gas development. It illustrates the value of developing a structured framework to allow assessment and benchmarking of geothermal resources. Furthermore, the nuances of modelling aquifer response and the behavior of enhanced water production as it travels from the reservoir to the process facilities are considered. The study shows that the production characteristics that favor geothermal energy adoption on a producing asset are elevated temperature profile, high water production rates, presence of injection support and/or artificial lift, and production lifespan. This study identified, assessed, and compared geothermal development models that might support geothermal co-production or repurposing of hydrocarbon assets. The result was a clear picture of near and long-term geothermal power options that are replicable across asset portfolios, that provides operators with additional strategies when considering lifecycle field activities and underlines the potential commercial value of including geothermal in field development. The study concludes that opportunities exist to generate meaningful geothermal power and offset emissions using existing production, examples of which will be presented and discussed.

Medical emergencies and on-going medical conditions on board may seriously impair seafarers' health and safety, and also negatively impact on future work prospects for seafarers. When a seafarer gets ill or injured on a ship, medical treatment often relies on the competences on his colleagues on board. The aim of this project was to establish a consensus-based minimum standard for medical education for seafarers, in order to ensure competency for adequate management of ill-health on board. International Maritime Health Foundation (IMHF) conducted a workshop on medical training of seafarers. A research-based approach to gain consensus on core learning outcomes/competences developed by the Tuning Project, has been used. This method was used by Tuning (Medicine) to gain consensus on core learning outcomes for primary medical degrees (Master of Medicine) across Europe. The result of the project is a set of learning outcomes/competences in medical training for merchant seafarers. The project resulted in a set of learning outcomes/competences on medical training of the seafarers that will be submitted to the relevant bodies of International Maritime Organization (IMO) in the process of the development of model courses 1.13, 1.14 and 1.15.

Life extension is an attractive option for subsea flexible risers nearing the end of their design lives. However, techniques for assessing accumulated fatigue damage in flexible risers are often associated with large uncertainties due to the simplified calculation approaches typically used. One approach to reducing uncertainties is the inclusion of nonlinearities in riser structural response and consistent linking between global and local models. In this article, we present the elements of a numerical multiscale procedure capable of predicting the stresses that lead to fatigue damage in flexible pipes, namely: a nonlinear beam element, a nonlinear section response model and a detailed finite element model; the consistent integration of models developed for different length scales; and finally a validation of the flexible riser large-scale model.

Abstract This paper presents two case studies of the seismic analysis of high pressure riser and conductor systems used on shallow water fixed platforms (approximately 120m water depth) offshore Newfoundland and Labrador, Canada. The case studies presented consider the Hebron and White Rose extension Husky gravity-based concrete platforms. A methodology is presented to assess the dynamic and resonant response of each conductor and riser system to seismic loading using a fully integrated conductor and platform interaction model. Seismic loading is an application of an earthquake-generated agitation to a structure. This occurs at contact surfaces either with the ground, or with adjacent structures, or with gravity waves. Nonlinear time history analyses of the riser system subjected to various ground motion records are performed to simulate the seismic load. Design considerations that drive the HP riser design are discussed. The paper addresses the intricacies of the gravity base concrete platform-riser system interaction, initial configuration and dynamic seismic response. The riser and conductor system response is used to determine HP riser connector and centralization requirements. The learnings taken from the detailed modeling method are presented along with the advantages of this methodology.

Abstract For ultra-deepwater subsea wells, a riser system is required to conduct completion, intervention/workover and end of life activities. For ultra-deepwater riser systems with high temperature and pressure requirements, the intervention riser system often requires vessel interface optimization to achieve acceptable design response. The upper riser can be configured in several different ways, each with its own benefit from a safety, risk and performance perspective. This paper compares the riser response for various vessel interfaces for ultra-deepwater applications. As discussed above, intervention riser structural response is sensitive to the riser configuration at the vessel interface. For a typical intervention riser, due to ultra-deepwater and high tension requirements, the functional tension load may utilize up to 40% of yield strength thus decreasing the capacity available to accommodate bending and pressure loads. Vessel operators have options to modify the system configuration to improve the strength and fatigue response of the riser. The different vessel interface options include the tension lift frame (TLF) to vessel interface, the top tension application method and the use or otherwise of a surface tree dolly. Upper riser assembly (URA) loads may be optimized by use of rotary wear bushings, a cased wear joint assembly or flexjoints as a part of the stack-up. The various riser-vessel interface options are evaluated and compared in this paper. This paper highlights the riser design challenges for ultra-deepwater applications.

This paper provides description and results from an investigation aimed to determine whether loading histories specific to marine and offshore structures cause shakedown of compressive residual stress produced by high-frequency mechanical impact (HFMI) treatment and therefore affect fatigue resistance of welded joints improved by these methods. Fatigue tests were carried out to investigate the influence of compressive fatigue loads on fatigue strength of non-load carrying specimens with transverse attachments subjected to ultrasonic impact treatment (UIT). It was found that significant relaxation of compressive residual stresses is achieved under application of compressive cycles in fatigue testing. It was also observed that not only the magnitude of the applied compressive stress/mean stress affects relaxation of the compressive residual stress but also the number of applied compressive cycles. This relaxation may reduce the beneficial effect of HFMI treatment under application of load histories specific to marine structures.

Drilling and intervention risers are widely used for oil and gas production in deep as well as shallow waters in oil fields around the world for subsea operations. The risers come in a diverse array of configurations, some of which may be challenged by fatigue if operated in high currents or seastates. The suitability of the selected riser and the operating limits are assessed by conducting strength and fatigue analysis based on design codes such as API RP 2RD, [7], API RP 16Q, [9], and API RP 17G, [10]. Typically, drilling and intervention activities are conducted for short periods of time but used repetitively. The codes are clear about the return period of the design environmental event which must be checked to insure safe operation with respect to strength; however, assessment of fatigue integrity can be more difficult to determine. The allowable fatigue operating environment should account for the ability to disengage, the time required to disengage, the damage rates in particular seastates, prior accumulation of fatigue damage, and variations in soil, tension and internal fluid weights. In this paper, an orderly method of establishing the allowable fatigue operation limits for drilling and intervention risers is presented based on Monte Carlo simulations along with a case study implementing the methodology in a shallow water environment. To illustrate this concept, a riser with wellhead and conductor system is assessed and is subjected to directional loading from several long-term seastates. The variation in effects is studied by doing fatigue analysis for different durations: 3 days, 1 week, 3 months, 1 year and 10,000 hours.

This paper describes the Delta House FPS Project topsides fabrication and integration contracted to Kiewit Offshore Services, Ltd. (KOS) by LLOG Exploration Offshore, L.L.C. (LLOG). KOS' work scope included the fabrication, loadout, heavy lift and integration of a 9,500 s. ton topsides structure using KOS' Heavy Lifting Device (HLD). Other notable work included the offload and marshaling of a 12,500 s. ton semisubmersible hull. Structural materials used in the construction of the topsides were higher API grade DNV approved plates and tubulars. KOS used European and domestic steel mills to supply topsides materials. The topsides structure was divided into several major sub-assemblies weighing between 100 and 5,000 tons each. All sub-assemblies were fabricated in-house in KOS' yard in Ingleside, Texas. Early Contractor Involvement (ECI) for the Delta House FPS project between KOS, Exmar Offshore Company (EOC), Audubon Engineering Company (AEC) and LLOG set the team up for success from the beginning. Prior to the start of fabrication, KOS was interfacing with engineering and LLOG operations teams. This involvement allowed KOS to provide input for a safer and more productive design, setting construction up for success with early contributions by all parties involved. The single level Exmar OPTI-EX topsides design made for simpler construction and equipment integration and allowed KOS to compress the schedule and deliver on-time. A single level deck design for a facility of this size necessitates careful planning of larger components and (sub) assemblies, which in turn allows for more efficient construction. The complete topsides structure was loaded onto a cargo deck barge and maneuvered under KOS' Heavy Lift Device where the structure was lifted and set onto the semisubmersible hull at the KOS bulkhead. Integration scopes were complete while the FPS was moored to the quayside allowing for productive and safe commissioning operations.

Abstract There are hundreds of kilometers of subsea pipelines around the world, forming a network for the extraction and transportation of oil and gas products. When near shore subsea pipelines cross shipping channels to ports, these pipelines can limit the size of the ships that enter the port. This is because the shallow burial depth of the existing pipeline can prevent any additional dredging required to deepen the shipping channel to accommodate larger vessels. An attractive solution under such circumstances is lowering the pipeline section throughout the width of the channel so that the channel can be deepened. The option of shutting the line down or installing a re-routed new line has cost implications. However, the alternative of lowering a pipeline while it is fully operational has engineering risk, operational challenges and the offshore industry is not very experienced in such projects. This paper presents a case study of such a key project where a 16" gas pipeline was successfully lowered from -3 m to -9m below the seabed whilst fully operational. The live gas pipeline was crossing a shipping channel and was buried at 3m below seabed. In order for the port to expand and allow bigger vessels to enter the port, the shipping channel needed to be deepened. Thus the pipeline was required to be lowered a further 6m for a stretch of 350m where the pipeline crosses the shipping channel. The lowering operations had to be carried out whilst the pipeline was fully operational as it was a 70km pipeline with key supply. This paper presents detailed overview into engineering challenges and operational issues faced on the project. The paper discusses all the stages of the project, risk assessments; integrity assessment for pipeline lowering; geotechnical assessment of trench stability; detailed pipeline lowering stress assessment; pre-operational planning; pipeline survey and pipeline lowering operation; post lowering integrity assessment. The pipeline lowering was successfully completed to meet the project requirement after 14 lowering passes. This successful lowering of a live gas pipeline by 6m is considered to be world's first such lowering. Recommendations on how a pipeline lowering project should be approached, assessed and executed are presented in this paper.