bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

AbstractThe 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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 (&gt; 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.