bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancing the Precision of Fatigue Analysis for Crucial Jacket Tubular Joints
Authors: Nekstad O. J. , Thomas A. P.
Published: April 2024

Offshore jackets and towers are examples of lightweight support structures for wind energy and oil and gas units. However, their reduced weight is obtained at the expense of increased susceptibility to fatigue failure because of their many welded connections. This study addresses the limitations of traditional analysis methods that primarily rely on parametric Stress Concentration Factors (SCFs) and basic beam theory, often leading to overly conservative outcomes, and proposes a methodology to revolutionize the fatigue analysis process by enabling the rapid creation of detailed 3D Finite Element (FE) models for tubular joints in a short time duration. The paper presents a comprehensive comparison between the advanced shell fatigue analysis and traditional beam methods, highlighting the former's superior accuracy in evaluating stress concentrations in complex joint geometries, thereby offering more precise predictions of fatigue damage. Through extensive case studies, the effectiveness of this advanced approach in accurately predicting fatigue damage in offshore jacket structures is demonstrated, showcasing its alignment with international standards like DNV-RP-C203 and significantly enhancing the precision of fatigue analysis. The study contributes to the offshore industry by improving safety and reliability, offering cost-effective design and maintenance strategies and facilitates the adoption of sophisticated analytical methods. This research offers an innovative methodology in fatigue analysis methods for offshore structures, setting a new benchmark for safer, more efficient, and technologically advanced practices in the offshore sector, thus ensuring the long-term sustainability and operational success of these crucial installations.
Emulsion Stabilized Hydrate Slurries: An Operational Flow Assurance Reality or a False Sense of Security?
Authors: Wylde Jonathan J. , Majid Ahmad A. A. , Bbosa Ben , Smith Rashod , Hernandez Oris , Asheim Colton , Patel Zubin
Published: April 2024

This paper provides a detailed case study on a lab-to-field strategy evaluating the use of flowline emulsions as a method of chemical-free hydrate control up to 25vol.% water cut. This is now ready to be put into successful operational practice in the deepwater production environment.

The oil in question was known to have a strong tendency to emulsify, and a detailed study of the separability of oil and water was necessary to understand the propensity for emulsions to form and more importantly break. Rheology studies were used to determine the thermal and shear influences on emulsion stability. These results better aligned the hydrate application testing performed using rocking cell and autoclave methods to determine hydrate formation under dynamic conditions and the propensity for hydrates to form at ever-increasing water cuts. Customized test protocols were required for the hydrate testing to better risk manage the nuanced aspects of hydrate formation including agglomeration amount and bedding (settling) propensity.

The emulsion testing showed a very stable and tight water-in-oil emulsion formed that didn't invert until >50vol.% water cut. The emulsions were rheologically complex and very temperature and shear dependent. At typical steady state subsea conditions, significant separation was not anticipated to occur up to and beyond 25vol.% water cut. Hydrate performance testing was able to demonstrate that at shear stresses approximating the flowline, 25vol.% water cut was able to remain emulsified for the whole of the test and was not available to create a significant hydrate slurry. At 30vol.% water cut significant hydrates formed and were deemed too operationally risky to go untreated. As of this time of writing, the field is not producing significant amounts of water requiring hydrate control, however the testing enabled a risk management approach that will require no hydrate control ("do nothing") for water cuts below 25% for extended shutdowns and cold restart scenarios. Flow assurance strategies and procedures are being updated to reflect this approach.

Taking advantage of the use of naturally occurring emulsions to solve deepwater hydrate flow assurance challenges is a novel and developing technique. Successfully risk managed cases are required to be shared with the industry to drive towards a lower carbon footprint production future coupled with less chemical exposure to the environment.
Study on Sand Production in Natural Gas Hydrate During Radial Wells Depressurization Exploitation
Authors: An Youkeren , Zhang Yiqun , Wu Xiaoya , Hasan Khanjar , Du Hongxing , Hui Chengyu
Published: April 2024

Radial wells are recognized as a promising type of well for achieving the commercial development of natural gas hydrate (NGH). Previous research has confirmed the positive impact of radial wells on enhancing the efficiency of NGH exploitation. However, the impact of radial wells on the reservoir intensifies pressure transmission and hydrate dissociation during the hydrate extraction process, significantly increasing the risk of sand production. Furthermore, in contrast to conventional reservoirs, hydrates in the South China Sea (SCS) are primarily hosted in unconsolidated argillaceous siltstone reservoirs. These reservoirs have poor cementation and weak stability, leading to an increased risk of sand production.

This study aims to investigate the issue of sand production in radial well exploitation by constructing a three-dimensional thermal-hydrologic-mechanical-chemical coupling model based on the reservoir parameters in the SCS. The analysis focused on variations in production capacity, sand production, and stress distribution between vertical wells and radial wells during the depressurization exploitation processes. Furthermore, a sand control standard is proposed to assess the impact of sand control on radial well exploitation.

The results show that: 1) Under the present simulation conditions, the annual gas production of radial wells is increased tenfold compared to vertical wells, but the problem of sand production is more serious. 2) Stress concentrations are the most serious problems that occur during hydrate exploitation, particularly in the near wellbore and perforation sections. 3) Raising the sand control standard for radial wells can effectively alleviate sand production issues but may lead to a decrease in exploitation efficiency. In summary, this paper offers valuable insights and guidance for managing sand production and sand control in NGH exploitation through radial well depressurization.
Low-Cost Below Seabed Monitoring Solutions for Monopile Foundations
Authors: Walker William P. , Williams Ryan S.
Published: April 2024

Monopiles are the most common type of foundation currently used in the offshore wind industry. Operators may elect to instrument and monitor foundations to assess the system behavior or support integrity management. For monopile foundations, the region below the seabed is critical since this region sees the largest bending loads in the monopile. The offshore wind industry can benefit greatly from sub seabed measurement systems as they can provide vital information regarding structural health and provide data to optimize future designs. However, installing sensors below the seabed is a non-trivial task that can occupy significant costs to engineer and implement such systems, which is a challenge in an industry that commands low-cost solutions. This paper presents an engineering study of two sensor cover concepts designed for implementation of sub seabed monitoring on a monopile foundation. The two concepts selected are designed to be fabricated from off-the-shelf components, producing a low-cost solution to sub seabed monitoring. Furthermore, the design relies on a combination of sub-scale testing and quasi-static analysis to reduce design costs and help support a low-cost solution.

Both strength and fatigue were considered in the design. Strength analysis was performed using a finite element analysis (FEA) where a series of acceleration loads, intended to represent the acceleration spectrum that would be present during pile driving, were applied to the protection systems in a quasi-static analysis. Additionally, a fatigue analysis is performed for the bolted connections on one concept using the stresses from the FEA. Two concepts were tested via a pile driving test with a sheet pile. The pile driving process was monitored and accelerations for each blow were measured during the testing. One of the two concepts tested survived the pile driving testing with accelerations measuring up to 900g, while the other failed.

The analysis and testing performed for this design showed that the sub seabed sensing on monopile foundations can be built from low-cost steel components, given proper collaboration between with the monopile designers/fabricators and the measurement system provider. Furthermore, this work has shown that sub seabed sensing for offshore wind monopile foundations can be done in a reliable, cost-effective manner that utilizes efficient design practices and is manufactured from commercially available, low-cost materials and components. Additionally, this work serves as an enabling solution for integrity management of offshore wind farms to help reduce operation and maintenance (O&M) cost.
Innovative Method for Large Corrective Maintenance of Floating Offshore Wind Turbines
Authors: Môre A. , Cermelli C.
Published: April 2024

Floating offshore wind turbines (FOWT) offer unique operational and maintenance (O&M) challenges and opportunities compared to their fixed-bottom counterparts. Situated further from shore, FOWT benefit from stronger, more consistent winds, but this increased distance leads to longer travel times and harsher conditions, reducing accessibility. Traditional jack-up vessels become impractical in deeper waters. Additionally, the inherent motions of FOWT introduce complexity to maintenance strategies.

As wind turbine dimensions continue to grow, major component replacements (MCR) require heavier lifts at greater heights. The conventional MCR approach for semi-submersible FOWT is the tow-to-port strategy, which can be complex, time-consuming, and costly. Consequently, there is a growing need to explore alternative onsite options.

This article introduces a novel floating-to-floating method for FOWT MCR, developed and numerically tested using a leading software for the dynamic analysis of offshore marine systems. The component to be replaced, also referred to as "package" below, is typically first removed from the wind turbine nacelle, and a replacement part is then re-installed. The method comprises: A motion-compensated offshore crane capable of lifting components and adjusting winch length based on the package relative distance from its target on the nacelle.Horizontal control lines (tag lines) connected to the package base, passing through deflectors at the nacelle top, and linked to winches or capstans.

To ensure a safe package transfer between the offshore crane and the nacelle, relative motion should not exceed a few centimeters when the package lands onto the nacelle. Numerical analysis results confirm that this method enables accurate transfers with low tension in the tag lines.

This innovative approach promises to enhance the efficiency and safety of maintenance operations for floating offshore wind turbines, addressing the unique challenges posed by their remote locations and size.
An Integrated Wave Energy Recharging System for Autonomous Underwater Vehicles
Authors: Mundon T. R , Rosenberg B. J. , Murrillo M.
Published: April 2024

This work presents an energy harvesting system that can be integrated into most autonomous underwater vehicles (AUV), allowing it to operate for significantly longer periods of time, potentially indefinitely. This wave-power charging capability is achieved by integrating a retractable reaction structure that can be stowed against the body of the AUV when not in use and two rotary power takeoff elements housed inside the AUV. The technology is applicable to most AUV's; however, this study focuses on implementation within a Lockheed Martin ‘EMATT’ vehicle, a small 4 7/8" torpedo shaped AUV.
Comparison of Fatigue Damage Caused by Wave and Wind for a Semi-Submersible Wind Turbine Structure
Authors: Wang Weihua , Gao Yidi , Song Chunhui
Published: April 2024

Floating wind turbine structures are subjected to complex fatigue damage resources, such as wave dynamic, blade motion, turbine vibration, wind turbulence, structure vibration and so on. A study of a semi-submersible wind turbine structure has revealed that the load from wind turbine significantly affects the fatigue behavior of the structure. However, how the load is comprised and how impacts fatigue life is unknown. Lately developed fully coupled time domain global analysis are capable of getting the time history of wind turbine tower bottom load. A study is performed to analyze the load the get the components of the loads. To get fatigue life of the whole structure, a complete structure model instead of hydro model is required. Due to the complication of the fully coupled time domain structural analysis, it is required to develop a methodology for coupling wind and wave impact on the fatigue life of the structure. In this study, time domain wind turbine load is used to compute the fatigue life due to wind and spectral fatigue method is used to computer fatigue life caused by wave. Then the fatigue damages were combined and compared to give suggestions for the future floating wind turbine structures.
Long Distance Motor Control Technology of Electric Submersible Progressive Cavity Pump in Deep Well Lifting, a Case Study
Authors: Huang Shouzhi , Hao Zhongxian , Zhu Shijia , Chen Qiang
Published: April 2024

The electric submersible progressing cavity pump (ESPCP) lifting technology has the advantages of rod-free pipe offset wear, low energy consumption, high system efficiency and high degree of digitalization. It is suitable for heavy oil wells, sand wells, gas wells, highly deviated wells, horizontal wells, platform wells and other complex condition of producing wells. ESPCP was widely used in recent years, and nearly 1,000 wells were applied in PetroChina. However, deep well lifting has been the bottleneck that electric submersible progressing cavity pump is difficult to break through. The deepest setting depth of pump of ESPCP in China was around 2,500 meters. With the increase of the setting depth of pump, the lifting capacity of the ESPCP gradually decreases, and the failure rate also increases. The fundamental reason is that the current variable-frequency drive cannot meet the needs of long-distance motor control.

In this paper, the terminal voltage and output power loss of the motor under the conditions of different cable lengths were analyzed through experiments, and the reasons for the power shortage of the long-distance motor were summarized. A novel long distance motor control technology of ESPCP based on vector control and revised filter was developed in this paper. A new vector control model suitable for long-distance motor control was established. The angle between dq-axis and stationary coordinate was calculated based on three-phase inductance of motor to get the maximum armature current. The compensation model was built according to the load and cable loss. At the same time, the inverter voltage was increased to 1140 V, and the motor structure was optimized.

The validity of the model was verified by experiments. Through the long distance drive experiment of ESPCP with new vector control technology, the actual output power of the motor was increased by 40% compared with the formed control method. ESPCP with this new control technology was carried out in Xinjiang oilfield, and the depth of pump setting was over 3,000 meters which was the deepest record of ESPCP application in China.

This long distance motor control technology of ESPCP provides an effective method to solve the low output power caused by long cable and overload, and the setting depth and applied range of ESPCP is extended.
Subsea Innovations and Technologies in Revitalization of Deepwater Brownfields in Brazil
Authors: Campos R. C. Lancelotti , Roberto M. , Campello G. C. , Capella da Fonseca M. M. , Orlowski R. , Moreira R. H. , Anna F. R. Sant' , Santana A. B.
Published: April 2024

The brownfields offshore Brazil comprise over 11,000 km of subsea pipelines and risers, 700 subsea Christmas-Trees and 60 manifolds, all interconnected with more than 50 platforms. These fields offer promising investment opportunities due to enhanced reservoir knowledge and the utilization of existing production infrastructure.

This paper presents a selection of subsea innovations and technologies developed to overcome the challenges associated with the revitalization, infill and subsea tieback projects of Marlim, Voador, Marlim Sul, Marlim Leste, Jubarte, Albacora, Barracuda/Caratinga, Roncador, Tartaruga Verde, and Espadarte brownfields.

A brief description of the subsea systems of the above-mentioned projects is also presented, as well as the main challenges associated with each one.
The Hybrid Composite Flexible Pipe: A New Generation of Flexible Pipe and a Definitive Solution for High CO2 Content Applications
Authors: Damiens A. , Miyazaki M. , Vraniskoski K. , Le Bourlegat L. , Correa P.
Published: April 2024

The paper aims at presenting the extensive qualification approach adopted for the Hybrid Composite Flexible Pipe (HFP). The test results presented are mainly focused on the capacity of the PEEK-Carbon Fiber composite material and the pipe to resist to harsh environment, which combines high CO2 content, high pressure, and temperature, demonstrating that HFP is a Stress Corrosion Cracking (SCC) resistant solution in ultra-deep-water environments.

The extensive testing campaign leveraged the classical pyramid approach described in DNV standard RP-A203, starting with material small scale to conclude on product full scale tests. The models developed aims at bridging the gaps from the idealized material level to full scale level. A comprehensive description of the testing done at the different scales to qualify the product for the most aggressive environments is given, including innovative methodology for end-of-life characterization for both material and the full-scale levels. Results of correlation between the experimental full scale prototypes tests and models are also provided.

At material scale level, a first step called fluid screening was conducted, aiming at identifying the most detrimental fluid to be conservatively used for all the subsequent small-scale testing campaign. The most significant finding is that the PEEK-CF composite material is inert to high contents of H2S. Additionally, there is no ageing of the material exposed to fluids with large CO2-content, demonstrating a good resistance and stability in CO2-rich environments. Results of the long-term properties measurement (fatigue and stress-rupture mainly) under continuous presence of high CO2-content fluid combined with high pressure and temperature, are also discussed. The permeation testing campaign revealed excellent permeation properties leading to a dramatic drop of CO2 partial pressure in the tensile armor wires annulus compared to conventional flexible pipe, making HFP a definitive SCC-free solution. Additionally, results of HFP full-scale tests done after months of CO2 saturation at high pressure and temperature have demonstrated a very good stability and behavior of the product over time. Finally, the paper presents the calculation model developed and compares it against the tests done at the medium scale and HFP full-scale levels, showing a very good correlation.

The Hybrid Composite Flexible Pipe is a breakthrough technology combining the best composite material and the conventional flexible pipes. The novelty of HFP lies in the ability to solve sustainably the SCC challenge, observed on conventional flexible pipes, for a service life of 30 years, allowing the safe use of this step-change flexible pipe technology in harsh and CO2-rich environments.
Roadmap for Repurposing Natural Gas Infrastructure for Hydrogen Storage and Transport - A Review of the Opportunities and Challenges
Authors: Raghu Damodaran
Published: April 2024

Energy transition requires the buildup of new infrastructure to produce, store, transport, transform (to e-fuels, eNH3 etc.) and utilize hydrogen through its entire value chain. The cost challenges for building new infrastructure are significant and must be built into the overall economics of the viability of hydrogen and energy transition. Alongside developing robust technology, significant work has also been done towards optimizing the new infrastructure to address cost challenges and make it at parity with existing energy solutions. However, considering the significant capital cost involved in building new infrastructure, the proposition to reusing, or repurposing existing assets to transport and store hydrogen is becoming increasingly attractive.

This paper addresses the viability of reuse and repurpose of existing infrastructure like natural gas pipelines to transport hydrogen (pure or co-transport). This paper articulates the drivers behind repurposing infrastructure like pipelines and what it would take to convert its service from natural gas to hydrogen in a safe and economically viable manner. This will include identifying the opportunities (technical, economic, and societal) and more importantly the challenges; and how best the challenges can be addressed within the prevailing economic and regulatory environments. Although much has been written about repurposing infrastructure, a concise guideline on the steps to take to repurpose is absent, since there is no straightforward answer. Repurposing must take into consideration the process, technical, human safety factors, assess the technical suitability of the asset for managing hydrogen and includes business analysis, infrastructure technical viability followed by rigorous analysis and testing. This paper attempts to develop a road map that would enable a business / operator with a protocol they can utilize to make decisions on repurposing.
Application of Neural Operator Technique for Rapid Forecast of CO2 Pressure and Saturation Distribution
Authors: Falola Yusuf , Rathore Pradyumna Singh , Nair Geetha Gopakumar , Toms Julianna
Published: April 2024

Geological carbon storage (GCS) is the most popular technique for sequestering CO2. Usually, GCS is modeled using commercial numerical simulators to make CO2 forecasts for mapping CO2 subsurface movement. However, simulators require high computational resources for complex problems. In this paper wavelet and Fourier neural operator (WNO and FNO) based – machine learning models were employed to rapidly forecast the reservoir pressure and CO2 saturation distribution, under fixed injection locations. Two geological models, SACROC and Sleipner, were used to generate CO2 injection datasets. The efficacy of the WNO model was evaluated through CO2 forecasts on the SACROC dataset, while the trained FNO model on the SACROC dataset was "transferred" to make predictions on the Sleipner dataset. The WNO-based ML method was accurate and efficient, such that the overall mean relative errors for pressure and saturation predictions on the test set were 2.21% and 0.84% respectively. More importantly, the WNO-ML algorithm reduced the prediction time by 90%. The overall mean relative errors for pressure and saturation prediction using transfer learning with the FNO algorithm were 2.48% and 1.79% respectively. Additionally, the application of transfer learning reduced the machine learning model training time and data storage requirement by 61% and 45% respectively. Through reduction of the computational time and data storage requirements for CO2 forecasting, transfer learning makes it possible to conduct more detailed and accurate forecasts, which can help to improve the safety and efficiency of CO2 storage projects.
Digital Twin: Hybrid Virtual Simulation and Physical Monitoring Strategy for Long-Term Safe Operation of Floating Production Platform-Hybrid Polyester Mooring Lines-Steel Catenary Risers Multibody System in the South China Sea
Authors: Chen Kejin , Yang Jin , Yin Qishuai , Mayank Tyagi , Gao Bingzhen , Song Zehua , Jia Shu , Liu Shuai , Xie Bin , Chen Hongsheng
Published: April 2024

As the first self-development ultra-deepwater gas field, the project adopts the floating production platform-subsea production system. The platform is kept in position by sixteen hybrid polyester mooring lines. The gas and other fluids associated to the production process are conveyed to the platform by six steel catenary risers. The field has an operational design cycle of 30 years.

With the purpose of ensuring long-term safe operation for offshore structures, this case fuses physical monitoring and virtual simulation to build an integrated platform management system. Monitoring data from the environment, platform, mooring lines and risers are periodically collected from the in-situ sensors. The system applies the Long short-term memory neural network to reconstruct the virtual simulation model of the dynamic response of offshore structures under environmental loads.

The system has two main functions: mechanical behavior prediction and mooring strategy adjustment. Combined with the monitoring data of environmental elements in the current operation area, the system can realize real-time prediction and calculation of platform movement, mooring lines tension and riser dynamic configuration, and visualize the health status of offshore structures. In case of severe operational conditions such as typhoon, the platform operators can obtain the platform displacement window and the corresponding mooring tension adjustment strategy through the operating system to maintain the riser stress safety.

This case gives a real-time solution for the safe operation of offshore structures with physical monitoring and virtual simulation, which can guide the operators to adjust the platform displacement to maintain the mooring lines and risers in the safety zone for a long time.
Buoyant Tower: Experimental and Numerical Studies on Novel Application of Suction Caisson Foundation
Authors: Lingyu Su , Xujie Pan , Rui Liu , Ge Wang , Zhichao Fang , Rui Dou , Weimin Chen
Published: April 2024

The buoyant tower, or BT, is a unique concept that stems from, and is a hybrid of, spar and compliant tower technologies. A BT is composed of one or a group of cylinders anchored to the seabed by a single suction caisson foundation (SCF). The BT rolls in a compliant manner while keeping the base from moving in any direction. The first application of BT is CX-15, a production platform in the Corvina Field offshore Peru. The 10-year-long operation since 2012 has provided a vast volume of data and experiences that support the IP-holder to re-visit this concept for extending the design to offshore wind, i.e., w.BT.

This paper summarizes a recent experimental and numerical study on SCF, one of the key components of a BT or a w.BT, subjected to cyclic loads. Unlike most of SCFs used for offshore O&G industries, the SCF of a BT or a w.BT needs to maintain adequate load-bearing capacities after enduring repeated rolling motions. The vertical loads come from the difference between the weight of the platform and the buoyancy, which varies with the draft changes due to waves and tides. The horizontal loads mainly come from cyclic wave loads on the hull. These conditions are seldom studied, and little is known about the bearing capacity of SCFs under such loading conditions. Also because of the unique configuration of the BT, there is no design guidance available in the existing standards that are fully applicable. The current study aims to understand the reduced vertical and horizontal load-bearing capacities of the BT's SCF after constant cyclic rolling as well as the failure mechanisms of the soil surrounding the SCF. The relevant working conditions were studied with 1:100 geotechnical centrifuge model tests. The bearing capacities of the SCF were carefully studied with a focus on reduction of the SCF's bearing capacity subjected to cyclic rolling of the BT. The test results were also used to calibrate a numerical analysis procedure that will be used for the design of SCF for w.BT.
Tapered WAG Ratio Optimization in an Egg Model With Brazilian Pre-Salt Fluid Using PSO Algorithm
Authors: Freitas V. R. , Sánchez William Humberto Cuéllar , Lima G. S. , Pastrana M. A. , Santos M. Gonzalez , Fortaleza E. L. F.
Published: April 2024

The Water Alternating Gas (WAG) is a well-established enhanced oil recovery method, which overpasses as waterflooding or gas injection. A particular type of WAG is the Tapered WAG which consists of varying the injection WAG ratio during the reservoir life instead of maintaining this parameter unchanged. In general, injection optimization may increase the cost function value, as the more complex and more parameters the technique has, the optimization becomes more time and computationally expensive. This is the case of the Tapered WAG, which makes its optimization unfeasible to be applied for real reservoirs. For this reason, to decrease the complexity of the problem, a Particle Swarm Optimization (PSO) is employed to optimize the Net Present Value (NPV) with only three variables of optimization, the water injection time equal for all injectors in three different pre-established periods. To explore other options, a PSO with twenty-four variables was also studied with different water injection times for injectors in the three periods. The PSO algorithm was applied in a modified version of the reservoir benchmark Egg model. The fluid compositions were replaced to mimic the Brazilian Pre-salt reservoirs, and some WAG and Tapered WAG of typical literature parameters were also tested. As a result, the NPV was improved by 10.44% in comparison to the waterflooding case, and it was the highest among the evaluated techniques.
High Pressure Hydrocarbon Separation Performance for Variation in Operational Parameters – Pseudo Dry Gas Systems
Authors: Bhaskoro P. , Johar J. , Liebana L. , Thomas L. , Wood T. , Roberson M. , Aman Z.
Published: April 2024

Pseudo Dry Gas (PDG) technology is proposed as an alternative concept for transporting multiphase fluids (gas, condensate, and water) for long deep-water subsea tieback developments while delivering significant reductions in Scope 1 and 2 CO2 emissions by the mitigation of compression (Liebana, et al, 2021)). The basis of the PDG system is to remove the liquid from the main pipeline using piggable liquid removal unit(s). With the removal of the majority of liquid, the shape of the internal resistance curve of the tieback is changed from a quadratic function to a linear function over the operational envelope, allowing the pipeline to operate like a "pseudo" dry gas system. The original prototype of this design underwent low pressure flow loop testing (Thomas, et al 2021)).

The current work involved the fabrication of a 180 bar rated PDG unit, a subsea magnetic drive pump and the supporting subsea control system for flow loop testing undertaken at TÜV SÜD National Engineering Laboratories (hereinafter NEL), UK. This development program is supported by operators in conjunction with the Net Zero Technology Center. The testing program is developed to encompass the expected operational envelope that the PDG units would see in service aligned to a broad range of asset-based study work and to consider critical non-dimensional flow assurance parameters to ensure scalability. The testing parameters considered are pressure (up to 125 bar), temperature (up to 40 C), and inclination (zero- and two-degrees). In addition, various liquids are considered e.g., two hydrocarbon fluids (representing oil and condensate), brine water, and hydrocarbon and brine water mixture.

An extensive number of test points at different liquid and gas superficial velocities are included both with and without the PDG unit installed to allow for baseline comparisons, with entrainment samples being collected upstream and downstream of PDG unit aligned to the Tulsa University technique (Bhaskoro, et al 2024). This paper will focus on how varying certain parameters including superficial gas velocity, superficial liquid velocity, and pressure impacts the separation efficiency and liquid entrainment. Some examples of mapping actual study results onto the high-pressure testing results are included to allow a greater understanding of required versus actual performance.

Results show comparable PDG separation performance at high pressure for all cases indicating negligible impact of higher pressures in relation to required performance as linked to the actual study cases.
Successful Advanced Foam Slug Injection to Inhibit Bottom Hot-Water Condensate Zone Channeling in First Horizontal Well Steam Flooding Pilot, Bohai Bay, China
Authors: Ma Kuiqian , Wang Yue , Pan Guangming , Li Hao , Yang Lijie
Published: April 2024

Nitrogen-foam was usually used in late steam breakthrough stage to modify channeling profile. It was demonstrated that a special hot-water condensate zone developed at the reservoir bottom due to vertical radial flow during horizontal well steam flooding. And the poor stability of hot-water condensate zone front affected the expansion of steam chamber at the reservoir top. The risk of channeling was higher in early thermal connection stage for horizontal well steam flooding.

It was showed that the higher the oil saturation, the smaller the foam resistance factor, but the foam can still be generated in the presence of oil, especially at the steam front with high water saturation. Based on indoor physical model experiments and reservoir numerical simulation method, a development technology for foam profile control was proposed during the early thermal connection stage. It was then carried out in field pilot 3 years ago.

Results showed optimal time for starting foam injection was water cut reaching 40%-60%. The recommended foam concentration was 1.5%, and slug size was 0.10PV. Under this strategy guidance, the steam-foam pilot test has been carried out for 3 years smoothly. Three foam slugs including 175 t foaming agent was injected with 62000 t steam during steam flooding pilot. During foam injection, slope of Hall curve increased, and resistance coefficient reached as high as 1.01∼1.34. The daily oil production of well group increased from 180 m3 to 250 m3. Meanwhile, water cut rising rate was only 3.9%, indicating the water cut increased very slowly. It was observed that foam played a significant profile control effect on the hot water condensate zone at the reservoir bottom. Also, inter-well connectivity direction changed gradually after each foam injection, and dominant steam flow direction increased from 2 to 4, which indicated steam chamber expanded more balanced. The wellhead pressure increased from 8.8 MPa to 9.2 MPa, only increasing 0.4 MPa, indicating there was no pressure building around injection well. This type of early foam profile injection did not affect the establishment of thermal communication between injection and production wells.

Different from traditional vertical well steam flooding, the timing of adding nitrogen foams was advanced. It was demonstrated that foam can effectively prevent steam channelling under high oil saturation conditions, especially at the steam front with high water saturation.
SLWR Design and Configuration Optimization Considering Strength, Interference, Wave and Slugging Fatigue Responses
Authors: Man Kevin , Yin Fengjie , Cao Peimin , Zeng Yifei , Firmian Michael , Hore Mainak
Published: April 2024

Steel catenary risers (SCRs) have traditionally been the preferred choice in offshore applications due to their simplicity and cost-effectiveness. However, in deep water with more challenging production conditions, SCRs present unique design challenges related to riser payloads and touch-down point (TDP) strength and fatigue responses. In contrast, steel lazy wave risers (SLWRs) have been gaining popularity as an alternative solution. This is primarily attributed to their ability to reduce the payload requirements on the host vessel and their capacity to effectively manage strength and dynamic response at the riser TDP. Nonetheless, the adoption of SLWRs introduces its own set of design complexities, including in mitigating slugging fatigue damage when transporting multiphase oil and gas through the SLWR system and interference with adjacent structure.

This paper focuses on the optimization design and analysis for a SLWR to meet strength, interference, fatigue design criteria considering extreme environmental loads and all fatigue sources while maintaining economic feasibility. OrcaFlex (Orcina 2022) is utilized to conduct strength, interference, and fatigue analyses for a series of riser configurations. To enhance analysis efficiency and reduce computational time, wave fatigue analyses are performed in the frequency domain.

Strength analysis results, obtained through nonlinear finite element simulations, are crucial for assessing the feasibility of proposed configurations. These results offer valuable insights into key parameters, such as the riser pipe size, hang-off angle, hang-off location on the vessel, sag bend and hog bend elevations, and azimuth angle. Among these parameters, sag bend height and arch height are identified as pivotal in defining the SLWR configuration. Total fatigue damages, encompassing installation fatigue damage, vortex induced vibration (VIV) and heave induced vibration (HVIV) fatigue damage, wave-induced vessel motion fatigue (WIF) damage, and slugging fatigue damage, are calculated. Mitigation methods based on the fatigue damage results are discussed.

SLWRs offer the advantage of reducing the payloads to the vessel while effectively mitigating critical stress and potential compressive forces at TDP. The slugging fatigue damage can be of significant concern when dealing with slug flow conditions. This paper introduces an enhanced and more efficient method for the development of SLWR configurations. Implementing this method, the buoyancy section length can be optimized. This, in return, leads to substantial reductions in project costs, making SLWRs a more economically viable choice.
Assurance Process and Technology for Riserless Interventions on Subambient Subsea Wells
Authors: Vick M. , Balaster P. , Ballard J. , Wates S.
Published: April 2024

As deepwater wells age and reservoir pressure drops, wells have the potential to enter a subambient state in which shut in wellhead pressure is below ambient seawater hydrostatic pressure. Standard intervention pressure control and completion equipment is typically designed to prevent positively pressured wellbore fluids from flowing to sea, not prevent the sea from flowing into the well, with pressure integrity evaluated based on net internal pressure, not net external pressure. This poses a multitude of risks ranging from developing hydrates in pressure control equipment to uncontrolled flow of seawater into wellbores or flowlines. Managing subsea riserless intervention operations in this state requires additional assurance at both an equipment component level and an operational execution level to maintain well control and execute operations safely.

A formal assurance process was developed to establish the integrity capability of subsea riserless intervention equipment under significant subambient well conditions (> 2,000 psi net external pressure). This was a collaborative effort between the operator, intervention vessel contractor, and original equipment manufacturers. Equipment was evaluated at both a component and system level to verify capability, and operating parameters and procedures were revised to maintain well control and well integrity under net external pressure conditions. The results of this process were formally documented to allow risks and safeguards to be clearly communicated to offshore personnel executing well intervention operations.

Multiple significantly subambient riserless well interventions have been executed by BP in the Gulf of Mexico and West Africa to-date. Multiple equipment options and intervention methods have been developed into standard operations, resulting in significant production uplift with no major incidents seen in operations relating to seawater ingress or intervention equipment failure due to net external pressure. As part of this process, BP applied for and received the first BSEE approval to allow consideration of external seawater hydrostatic pressure to develop a depth adjusted working pressure for subsea intervention equipment.
Expanding the Boundaries on Material Selection for Additive Manufacturing (AM) Technologies: An Investigation of N08904 AM Manufactured Alloy Mechanical & Corrosion Properties as an Alternative to Ni-Based AM Manufactured Alloys
Authors: Sanchez-Valverde A. , Yuang X. , Signorelli R. , Elsayed A.
Published: April 2024

This paper explores the potential of N08904 as an alternative alloy to Ni-based alloys in the Oil & Gas industries by characterizing the mechanical and corrosion properties of Laser Beam Powder Bed Fusion (PBF-LB) manufactured samples and comparing the results against rolled flat material of the same alloy. As of today, Oil & gas industries are slowly adopting AM technologies to produce some of their parts. However, regarding material selection, the possibilities are scarce, as the investigations are focused on proving the feasibility of different AM technologies using mainly highly alloyed Ni-based materials or standard stainless steels such as S31603.
Technology Deployment in Deepwater Projects – The Bonga Example
Authors: Aramanadka S , Adebola D. , Amuda D. T. , Anyankpele D. , Giwa O. F. , Wemimo O. , Osolu O. , Ishie A. , Agbabiaka O.
Published: April 2024

This paper presents some of the technologies that were deployed by the Deepwater Projects & Engineering (DWP) team in the Bonga field to enhance production, reduce deferment and maintain asset integrity. This paper is one of a series of Bonga themed papers for OTC 2024. Noteworthy amongst the deployed technologies are:

A Smart Isolation Plug (smart plug) which was deployed during the first-of-its kind replacement of the gas export (GE) riser flex joint (FJ) in the Gulf of Guinea to reduce production deferment and flaring while mitigating the risk of loss of containment during continuous production. The smart plug eliminated the need to depressurize the 100 km GE pipeline (an ~6-8 days activity), which would have resulted in ~30 MMscf/d gas flaring for ~4 days and significantly reduced the GHG (Greenhouse Gases) emission impact of the FJ on Bonga. This also eliminated the requirement to repressurize upon project completion which would have required an additional 1-2 days. Thus, the Smart Plug provided ~16 days saving to the project execution schedule.

The laser scanning which is built on imaging technology and enabled faster project delivery through Asset visualization, ensuring faster and increased accuracy in Engineering and Fabrication through dimensional control and for corrosion management. Other immediate benefits included quick turnaround of As-built updates, reduction of GHG emissions and safety exposure from offshore flights/travels through the Bonga i-site Asset Visualization Portal.

The Structural Digital Twin (SDT) which is capable of on-demand assessment of the Hull and the Topsides structures of the Bonga FPSO (Floating Production Storage and Offloading). It provides leading performance indicators, ascertains the current health of our facilities including the Safety Critical Structures, enables proactive maintenance planning and evaluation for future conditions related to tie back and life extension. It also enables an organized way of reporting FPSO performance that improvises the approval process with Class society.

ROV installable Anodes is vendor technology that was available for subsea structures. It was considered for mooring, internalized for use on the Bonga FPSO mooring chains and has helped to slow down the uniform corrosion rate. Implementation of this technology as barrier against material loss provides an in-situ remedy for brownfield application thereby enhancing assurance related to asset integrity to mitigate the loss of station keeping.

This paper provides an overview of the successful deployment of some technologies by the DWP team on the Bonga field's journey to the production of one billion barrels of oil. Industry professionals can leverage information in this paper to successfully execute projects on their own journey to achieve more production/less deferment while maintaining asset integrity.
CFD-Based Numerical Wave Basin for Floating Offshore Wind Turbines
Authors: Jang Hyunchul , Jang Hakun , Teng YihJeng
Published: April 2024

This paper introduces a novel coupled analysis methodology for predicting the global responses of floating offshore wind turbine (FOWT) platforms using high-fidelity Computational Fluid Dynamics (CFD) analysis. The hydrodynamic behavior of the floating platform subjected to waves and current is solved by T.EN's CFD-based numerical wave basin tool (MrNWB), and the aerodynamic, aeroelastic, and servo-dynamic behaviors of a wind turbine are solved by NREL's wind turbine simulation tool (OpenFAST). The present numerical wave basin tool is called Wind Turbine Numerical Wave Basin (WTNWB) and is capable of providing wind-turbine performances and tower structural responses as well as 6-DOF platform motions and mooring tensions in high-fidelity. The coupled analysis demonstrates excellent agreement with the model test in the prediction of platform motions and mooring line tensions. WTNWB can overcome known drawbacks of two types of physical model testing methods: full physical model testing and real-time hybrid model testing. WTNWB is now ready to be used in FOWT projects for global performance analysis and is capable of more complicated test cases to consider blade elasticity, pitch control, and other possible sensitivity tests available in OpenFAST.
Integrating Dual-Parameter Soil Classification with CPT-Driven Machine Learning for Site Investigation of Offshore Wind
Authors: Li Zhichuan , Zhang Zijian , Lei Xinhai , Lao Jingshui , Li Ya
Published: April 2024

Accurate geological characterization is crucial in offshore engineering projects. This study aims to develop an advanced methodology that extends the application of Cone Penetration Testing (CPT), providing a more precise and detailed classification of subsurface soils in the locations without coring. Then, the methodology integrates advanced techniques to achieve precise geological characterization. It initiates with a dual-parameter clustering analysis, a process pivotal in uncovering nuanced geological insights. Submerged unit weight and undrained shear strength, recognized as primary indicators, are meticulously examined in the designated coring sites. The K-means algorithm, a unsupervised machine learning technique, is employed in this clustering analysis. It iteratively refines the classification by strategically grouping data points based on their proximity in the dual-parameter domain. Then, a Convolutional Neural Networks (CNN) architecture is designed to synthesize the outcomes of the clustering analysis with the extensive dataset obtained from Cone Penetration Testing (CPT). This network undergoes a training process using a combination of current program data and historical datasets from various regions.

This integrated approach capitalizes on the strengths of both Kmeans clustering and neural networks. While Kmeans excels in identifying patterns and grouping data points in a two-dimensional space, neural networks are adept at learning complex relationships within data. By combining these methodologies, the study achieves a synergistic effect, resulting in a highly accurate and detailed classification of subsea soils. Compared to conventional CPT classification methods, our approach demonstrates superior precision and granularity. By incorporating dual-parameter clustering and machine learning, the methodology refines geological classification and description, providing a more comprehensive understanding of the physical properties of subsea soils.