Floating Production Storage Research Articles

Underwater Line Monitoring Using Optimally Placed Inclinometers

Underwater monitoring presents challenges related to maintaining a continuous power supply and communication, necessitating the use of a smaller number of sensors to effectively cover the entire line. An underwater line tracking method is proposed to evaluate global behaviors and stresses in real time. The method employs angles at several points on the line, as well as displacements and curvatures at both ends. In this method, any line displacement, angle, and curvature are expressed as Fourier series, and Fourier coefficients are obtained by utilizing sensor data. Then, the behavior of any line location is assessed. In addition, to reduce the number of sensors and improve accuracy, optimal inclinometer locations are determined by a genetic algorithm. The proposed line tracking algorithm was validated through two numerical examples; one with an inclined tunnel and one with a marine steel catenary riser attached to a Floating Production Storage and Offloading (FPSO) vessel. Through these examples, the proposed algorithm was proven to capture global behaviors accurately when optimally located sensors are used. In the riser monitoring case, the optimized sensor placement with eight intermediate sensors achieved an average mean distance error of 1.91 m, which is lower than the 2.65 m error obtained with ten intermediate sensors without optimization.

Structural Evaluation on the Floating Production Storage and Offloading Large Flow Gas Processing Module Based on FEM Analysis

The floating hoisting of floating production storage and offloading (FPSO) production modules introduces substantial challenges due to the propensity for excessive deformation within the typical tubular truss structures during operations. This research proposes a temporary reinforcement scheme, leveraging finite element method simulations under wind, wave, and current loads, to mitigate deformation concerns. Utilizing DNV GeniE software, this study establishes a finite element model, simulating the floating lifting process and conducting a comparative analysis between pre- and post-reinforcement scenarios. The results demonstrate a significant reduction in maximum stress and deformation, substantiating the efficacy of the reinforcement strategy and underscoring the safety and reliability of such operations. The successful execution of this methodology heralds a promising avenue for marine engineering practices, advocating for the optimization of large-scale offshore module installation.

Maritime Inventory Routing with Speed Optimization: A MIQCP Formulation for a Tanker Fleet Servicing FPSO Units

This paper presents a continuous-time formulation for the management of deep-sea floating production storage and offloading (FPSO) units, which process and store crude oil from nearby oil platforms while waiting for a shuttle tanker to arrive and collect it. A heterogeneous fleet of tanker vessels travelling between the FPSO units and a port refinery is available, with the optimization deciding on the number and type of vessels to use, their route and travelling speed. The goal is to achieve an environmentally friendly solution featuring vessels travelling at lower speeds to minimize fuel consumption (a quadratic function of speed), which may require renting additional shuttle tankers to maintain production. The resulting mixed-integer quadratically constrained problems (MIQCP) can be solved by GUROBI, but not to global optimality, whereas a mixed-integer linear programming (MILP) relaxation that underestimates the total operating cost can tackle moderate problem sizes (5 FPSOs and 4 shuttle tankers).

VFD-based Coordinated Centralized/decentralized Control to Support Offshore Electrical Power Systems with Wind Power Penetration

This paper proposes a coordinated centralized/decentralized control designed to concomitantly manage the power factor and mitigate voltage variations at the main feeder of an oil and gas offshore platform. The centralized action (i.e., power factor control) is decoupled from the decentralized one (i.e., voltage support) due to the significant disparity in dynamics of the commands sent to the active front-end variable frequency drives (AFE-VFDs). The AFE-VFDs are embedded with a proposed V-Q inverse droop curve, while being remotely coordinated by a central controller using a low-bandwidth communication link. Unlike other strategies, the proposed control is effective in handling unplanned events and unpredictable disturbances. Simulations are conducted to compare the proposed strategy with a literature solution considering a typical Brazilian floating production storage and offloading platform, from Mero Oil Field.

Numerical simulation and measurements on reduced scale structures of floating production storage and offloading units

Protecting offshore structures against the effects of lightning strikes, sparks, and short circuits is a considerable challenge to designers and deployment engineers once the numerous exposed structures, pieces of equipment, and devices make the behavior of electromagnetic phenomena difficult to predict. Numerical simulations are important tools to predict such behavior. However, due to the uncertainties involved, they should be compared against laboratory results. This paper presents the results of the measurements performed on three scaled models and compares them to those obtained with two different applications, CST Studio Suite and NEC-4. We elaborate hypotheses regarding the differences between laboratory results and those obtained using simulation software. As an application, after validating modeling techniques, the paper discusses the results of induction on cable loops on “gooseneck” chimneys commonly used in ships and floating production storage and offloading units.

Predicting heave and pitch motions of an FPSO using meta-learning

Real-time motion prediction is helpful in guaranteeing the operation stability of a Floating Production Storage Offloading (FPSO) unit. Recurrent neural networks (RNNs) are becoming feasible alternatives to numerical simulations for motion prediction as artificial intelligence develops rapidly. In this study, model-agnostic meta-learning (MAML) is combined with RNNs to deterministically predict the heave and pitch motions of a ship-shaped FPSO. This approach is motivated by the fact that MAML improves training efficiency without losing accuracy. The data came from a scaled model test conducted at Shanghai Jiao Tong University’s deepwater wave basin. Before introducing MAML, we verified that long short-term memory (LSTM) and gated recurrent unit (GRU) could accurately predict the heave and pitch of about 7.68 s into the future. With fewer learnable parameters than LSTM, GRU demonstrates slightly better accuracy. Therefore, this study focuses particularly on the combination of GRU and MAML. The parameters of MAML, including order of derivative, step size, number of adaption gradient updates, and batch size of the tasks, are evaluated systemically in terms of accuracy and training efficiency. With the assistance of MAML, GRU’s training efficiency for heave and pitch has significantly improved, increasing by approximately 65% and 55%, respectively. Meanwhile, the prediction error for both has decreased by about 10%. Notably, MAML’s performance is minimally affected by variations in incoming wave direction and sea state, as well as the randomness and temporal variability of the motion. MAML is a powerful tool that enables RNNs to achieve real-time prediction of FPSO motion.

Experimental Characterization of Stiffness of a Polyester Mooring Rope for a CFPSO

Synthetic ropes are increasingly favored for use in offshore systems. Accurate predictions of the coupled hydrodynamic performance and structural response of offshore structures depends on a thorough understanding of the nonlinear characteristics of fiber materials. The objective of this study is to experimentally characterize the stiffness of a polyester mooring rope for a cylindrical floating production storage and offloading system. The quasi-static stiffness of the ropes and aged ropes after installation and the dynamic stiffness in various loading conditions were computed based on sub-rope tests following the guidelines from the American Bureau of Shipping. The quasi-static stiffness curves exhibited a linear decrease in values as the logarithm of the loading period (in minutes) increased. The dynamic stiffness was, in general, much higher than the quasi-static stiffness. The dynamic stiffness under various loading conditions revealed the complexities of the mechanical properties of polyester rope. Parameters such as the mean load, load amplitude, loading period, and loading cycles all had a notable impact. More tests are required to have a better understanding of their effects.

Petroleum exploration and production in Brazil: From onshore to ultra-deepwaters

The Santos Basin in Brazil has witnessed significant oil and gas discoveries in deepwater pre-salt since the 21st century. Currently, the waters in eastern Brazil stand out as a hot area of deepwater exploration and production worldwide. Based on a review of the petroleum exploration and production history in Brazil, the challenges, researches and practices, strategic transformation, significant breakthroughs, and key theories and technologies for exploration from onshore to offshore and from shallow waters to deep–ultra-deep waters and then to pre-salt strata are systematically elaborated. Within 15 years since its establishment in 1953, Petrobras explored onshore Paleozoic cratonic and marginal rift basins, and obtained some small to medium petroleum discoveries in fault-block traps. In the 1970s, Petrobras developed seismic exploration technologies and several hydrocarbon accumulation models, for example, turbidite sandstones, allowing important discoveries in shallow waters, e.g. the Namorado Field and Enchova fields. Guided by these models/technologies, significant discoveries, e.g. the Marlim and Roncador fields, were made in deepwater post-salt in the Campos Basin. In the early 21st century, the advancements in theories and technologies for pre-salt petroleum system, carbonate reservoirs, hydrocarbon accumulation and nuclear magnetic resonance (NMR) logging stimulated a succession of valuable discoveries in the Lower Cretaceous lacustrine carbonates in the Santos Basin, including the world-class ultra-deepwater super giant fields such as Tupi (Lula), Mero and Buzios. Petroleum development in complex deep water environments is extremely challenging. By establishing the Technological Capacitation Program in Deep Waters (PROCAP), Petrobras developed and implemented key technologies including managed pressure drilling (MPD) with narrow pressure window, pressurized mud cap drilling (PMCD), multi-stage intelligent completion, development with Floating Production Storage and Offloading units (FPSO), and flow assurance, which remarkably improved the drilling, completion, field development and transportation efficiency and safety. Additionally, under the limited FPSO capacity, Petrobras promoted the world-largest CCUS-EOR project, which contributed effectively to the reduction of greenhouse gas emissions and the enhancement of oil recovery. Development and application of these technologies provide valuable reference for deep and ultra-deepwater petroleum exploration and production worldwide. The petroleum exploration in Brazil will consistently focus on ultra-deep water pre-salt carbonates and post-salt turbidites, and seek new opportunities in Paleozoic gas. Technical innovation and strategic cooperation will be held to promote the sustainable development of Brazil's oil and gas industry.

Real-time dynamic and structural behavior estimation of a steel lazy wave riser through finite-element-based digital twin and hull-motion sensor

A digital twin (DT) method is proposed to estimate the dynamic and structural behaviors of a Steel Lazy Wave Riser (SLWR) under environmental conditions. This method uses a 1D finite element (FE) riser model that can include various loads and boundary conditions measured from sensors. We selected a spread-moored Floating Production Storage and Offloading (FPSO) vessel to validate the proposed method, which hosts multiple Production and Injection SLWRs. Using the time-domain dynamics simulation program, we built a reference model considering the fully coupled FPSO with mooring lines and risers in various wind/wave/current conditions. The synthetic sensor data, which represents the motions and internal fluid density changes, were generated from the simulation of the reference model. Then, two riser DT models, the Top Oscillation Model (TOM) and the Two-Point Oscillation Model (TPOM), were built, considering only a single riser made of the 1D FE model. TOM employed vessel motions as boundary conditions while internal fluid density and ocean current could be inputted as external loads. TPOM incorporated an additional motion sensor attached to the riser. The motion data obtained from the reference model were first inputted into the respective riser DT models. Next, we further evaluated their performance with and without the estimated ocean currents and slugs of internal fluid. The time histories, spectra, and statistical data of displacements and stresses along the riser were systematically compared and analyzed for various test cases and environments. While the hull-motion sensor alone can provide practically acceptable results using the developed methodology, additional consideration of current load and internal fluid's density variation improves the overall riser monitoring performance. The present method can significantly reduce the number of sensors compared to traditional riser monitoring methods.

FPSO/LNG hawser system lifetime assessment by Gaidai multivariate risk assessment method

Floating Production Storage and Offloading (FPSO) unit being an offshore vessel, storing and producing crude oil, prior to crude oil being transported by accompanying shuttle tanker. Critical mooring/hawser strains during offloading operation have to be accurately predicted, in order to maintain operational safety and reliability. During certain types of offloading, excessive hawser tensions may occur, causing operational risks. Current study examines FPSO vessel’s dynamic reactions to hydrodynamic wave-induced loads, given realistic in situ environmental conditions, utilizing the AQWA software package. Current study advocates novel multi-dimensional spatiotemporal risks assessment approach, that is particularly well suited for large dataset analysis, based on numerical simulations (or measurements). Advocated multivariate reliability methodology may be useful for a variety of marine and offshore systems that must endure severe environmental stressors during their intended operational lifespan. Methodology, presented in this study provides advanced capability to efficiently, yet accurately evaluate dynamic system failure, hazard and damage risks, given representative dynamic record of multidimensional system’s inter-correlated critical components. Gaidai risk assessment method being novel dynamic multidimensional system’s lifetime assessment methodology. In order to validate and benchmark Gaidai risk assessment method, in this study it was applied to FPSO and potentially LNG (i.e., Liquid Natural Gas) vessels dynamics. Major advantage of the advocated approach is that there are no existing alternative risk assessment methods, able to tackle unlimited number of system’s dimensions. Accurate multi-dimensional risk assessment had been carried out, based on numerically simulated data, partially verified by available laboratory experiments. Confidence intervals had been given for predicted dynamic high-dimensional system risk levels.

Port State Control of Offshore Supply Ships, MODU and FPSO Units

The Port State Control system aims to ensure that all ships are subject to regular inspections, with particular attention to the ships of insufficient quality. To this end, during the inspection, priority is given to ships that are considered risky. Thetis database is an information system that contributes to the implementation of the Port State Control within the EU (European Unit). It contains data on inspections performed in the EU ports and the Paris Memorandum area. The Paris Memorandum has 27 member states and covers the waters of European coastal states and the North Atlantic basin from North America to Europe. The main goal of the Paris MoU (Memorandum of Understanding) is to eliminate substandard ships through a harmonized Port State Control system. Namely, inspections should ensure that ships meet international safety standards, are safe for the environment, and provide adequate living and working conditions for workers. The primary responsibility for ensuring these standards rests with the ship owner/shipper while the responsibility for ensuring such compliance rests with the flag state. The aim of this analysis is to determine the number of inspections performed in the ports of the Republic of Croatia and the Republic of Italy, to identify the cause of ship detentions and the most common deficiencies of offshore supply vessels, MODU (Mobile Offshore Drilling Units) and FPSO (Floating Production Storage and Offloading) Units. In the observed period, the impact of the crisis caused by the COVID-19 pandemic was significant, resulting in the decline in the numbers of inspections performed in 2020 and 2021. In 2022, the number of inspections increased, but it still has not reached its pre-pandemic level. During the period that was the subject of research, port state inspections in the Republic of Croatia and the Republic of Italy revealed 241 deficiencies. Five areas with the largest number of deficiencies are: Certificate & Documentation, Safety of Navigation, Fire Safety, ISM, and Life-saving appliances, which follow the trend of the lack in the areas of the Paris Memorandum. The greatest increase in deficiencies was recorded in the areas of Labor Conditions-Health protection, Certificate & Documents (Crew Certificate, Documents), Emergency System and Fire safety area, which led to an increase in the number of offshore supply ships retention during the first half of 2022.

A bowtie model for fuel gas leakage incidents in an FPSO engine room

Safety and operational costs are of paramount importance in offshore facilities. Efforts to find new ways to reduce operational costs and minimize risks have led to the development of techniques in the field of safety. Routine checks and equipment maintenance are conducted based on either calendar periods or equipment uptime, using conditional monitoring, to prevent malfunctions through preventive maintenance (PM). PM is a key strategy for ensuring the integrity and process safety of safety barriers in offshore facilities. However, due to challenges in modeling dependencies, determining maintenance intervals, and updating belief in operational data, ineffective safety barriers can occur and lead to incidents. Excessive maintenance can also increase the risk of operational mistakes among workers. This study examines safety and operational issues associated with fuel gas leak events caused by various risk factors in Floating Production Storage and Offloading (FPSO) engine rooms using the bow-tie model. Within this context, safety barriers are defined, encompassing both preventive controls and mitigating measures that can be employed to minimize potential risk factors. Furthermore, the study underscores the importance of maintenance intervals for a specific set of safety barriers, necessitating periodic testing using Condition-Based Maintenance (CBM) tools for FPSO units.

Assessment of a Full-Electric Floating Liquefied Natural Gas Concept for Harsh Sea State Conditions at Remote Ultra-Deepwater Locations

_ This work describes an offshore gas monetization solution for harsh environmental conditions at ultra-deepwater and remote locations, as an alternative to conventional onshore plants associated with long subsea pipelines for Greenfield projects. Although gas-to-liquids and marine compressed natural gas are initially evaluated, associated gas is supposed to be exported from deepwater floating production storage and offloading units to a central floating liquefied natural gas (FLNG) facility for additional treatment, fractionation, and liquefaction, producing liquefied natural gas (LNG) and liquefied petroleum gas (LPG) for further tandem offloading. To demonstrate the technical feasibility of the proposed FLNG, its key technologies are reviewed, including liquefaction process selection, cargo containment system, station-keeping, offloading, and power generation. A full-electric FLNG is proposed, replacing conventional feed gas power generation systems with inner hull nuclear power modules, envisaging neutral CO2 emissions and earlier first LNG drop milestone achievement. The FLNG general arrangement is developed, along with its internal cargo tanks layout, for preliminary LNG and LPG production rundown and feed gas throughput. Numerical analyses are carried out to show that static and dynamic tilt criteria can be met, even for harsh sea states. Gas import riser configurations for the challenging ultra-deepwater location are outlined, after appropriate FLNG station-keeping analyses, in addition to a feasibility assessment of seawater intake risers, aiming for an overall gas plant efficiency increase. Keywords FLNG; FPSO; LNG/LPG; associated gas; design (general)

Design and numerical simulation of the elastomeric support for the topside modules of an FPSO

Elastomeric support utilizing steel-reinforced elastomeric bearing pads (SREBPs) has been applied to offshore structures gradually. This study presented a process for designing the offshore elastomeric support. And a specific numerical method was introduced to synchronously simulate the hydrodynamic responses and structural interactions between hull and topside modules of a spread-moored floating production storage and offloading (FPSO) unit with elastomeric-supporting topside modules. Furthermore, a model test of the target FPSO was conducted in a deepwater offshore basin to validate the numerical simulation, and the numerical results were consistent with the experimental outcomes overall. The numerical results demonstrated that both bearing force and stress of the SREBPs fell within the design scope, and the maximum bearing force on vertical SREBPs was found to be around 1.3 times the weight of a corresponding topside module, considering the dynamic effects resulted from motion responses of the FPSO. Additionally, the maximum bearing force acting on anti-uplift SREBPs can refer to the peak value of a vertical SREBP's dynamic force correspondingly. The horizontal interactions between hull and topsides mainly depend on inclination of the hull, so the bearing forces of horizontal SREBPs are closely related to the severity of rolling and pitching.

Wave-induced vibration control of Floating production storage and offloading systems by tuned mass damper inerter

Wave-induced vibration control of Floating production storage and offloading systems by tuned mass damper inerter

Numerical study for slamming loads on the bow of a ship-type FPSO model under breaking waves

Numerical analyses were performed to investigate the characteristics of the slamming impact loads on the bow-flare of a ship-type floating production storage and offloading (FPSO) model under breaking waves. To estimate the slamming impact load, a series of breaking wave simulations was performed. From 2D wave flume tests, the grid aspect ratio, convection scheme, turbulence model, effect of surface tension, and grid dependencies were investigated. Through a series of numerical simulations, the grid system and numerical schemes were determined, and the slamming impact load simulations were conducted. It could be observed that the slamming impact loads and motions of the FPSO model in the numerical simulations were in good agreement with the experimental results. In order to investigate the relation between the slamming impact load and free motion of the FPSO model, the breaking impact simulations were performed under fixed positions and the free motion of the FPSO model. From the results, the relation between the relative angle and slamming impact load, as well as the relation between the position of the FPSO model and impulse response, are discussed.

Reliability of permanent downhole systems: Minimum sample and quality index

Permanent downhole monitoring systems are responsible for measuring pressure and temperature time series and enable uninterrupted reservoir characterization during the oil field production period, playing a key role in the oil and gas industry. Located in hostile pressure and temperature environments (i) close to the reservoir, in the case of the PDG (Permanent Downhole Gauge) sensor, and (ii) at the wellhead, in the case of the TPT (Pressure and Temperature Transducer) and PT (Pressure Transducer), its data are transmitted from the subsea environment to the Floating Production Storage and Offloading (FPSO), where the Master Control System (MCS) provides the information in engineering format. This information fulfills its function in the FPSO plant and finally is stored in an onshore data historian. Such complexity, importance, and maintenance difficulty of this system make it necessary to control and manage its reliability. Therefore, the objective of this work is to increase the availability and maximize the useful life of the downhole permanent monitoring system through the reliability calculation, using the Weibull estimate with 2 parameters, and the application of an index quality of statistical inferences. The proposed method for estimating reliability uses a database containing information from permanent downhole monitoring systems of the PDG, TPT, and PT type, from January 1st, 2008 to January 9th, 2014, and considers only the failures that occur until the arrival of the data in the MCS. From the reliability results, it can be observed that stratifications of this database could generate samples with a smaller number of observations, thus inferring reliability even with a small number of samples. The deepening of this method results in the definition of the minimum sample that allows removing reliability inferences without statistical significance and a quality index that allows classifying the reliability estimates of stratified sets of the largest sample of a database. It is worth mentioning here that both methodologies developed in this work are inserted in a well monitoring system that intends to contribute to increasing the availability of pressure and temperature data for the management of well operations.

Analysis of The Effect of mooring Depth & Fatigue Damage on Mooring Line FPSO Ship Azurite In The Masela Block

Oil & gas drilling in the open sea cannot be avoided with the use of FPSO. Floating Production Storage and Offloading (FPSO) is a facility in the form of a floating production storage and unloading vessel in the form of crude oil and natural gas originating from the seabed. The selected type of floater that will be operated in the Abadi field, Masela Block, Arafura Sea is the Azurite FPSO ship. In its operation, the FPSO will not be separated from the influence of dynamic loads such as sea waves, ocean currents and wind on the mooring rope structure periodically. This may cause damage to the structure mooring line which influences the performance of the structure. The aim of this research is to analyze motion trajectory (surge and sway), mooring line stress, and fatigue damage on the mooring system catenary by making comparisons using variations in mooring depth. Dimensions mooring line type chain on fairlead with six (6) variations in mooring depth, namely 1000, 900, 800, 700, 600 and 500 meters which will then be analyzed fatigue damage from mooring line the. Observation result Motion Trajectory It was found that the shallower the mooring depth mooring line then value ∆Offset or movement surge & sway will get bigger. Meanwhile in observations Mooring Line Stress and Fatigue Damage obtained both are directly proportional where the greater the tension mooring line then the ratio of damage that occurs due to fatigue in the structure will also be greater. This is because the mass of the rope used is not proportional to displacement boat. And in this numerical analysis simulation it only reaches the initial movement, namely at 100 seconds, where the ship's condition has not yet reached the stable condition it should be.

Mooring Design and Fatigue Damage on Variant Fairlead Positions During FPSO Operation – Case Study

This comprehensive case study delves into the intricate dynamics of deepwater mooring systems, specifically focusing on Floating Production Storage and Offloading (FPSO) operations. Our investigation centers on the Anoa Natuna FPSO, situated in the Arafura Sea. We examine how varying fairlead positions, employing a 4x3 chain configuration, influence structural integrity, operational stability, and fatigue damage. The research meticulously analyzes the response of the FPSO to environmental forces, providing a detailed understanding of the vessel's behavior under different fairlead positions. The results showcase the vessel's stability, elucidate variations in its motion response, and highlight the effects of fairlead positioning on structural fatigue, offering valuable insights for safe and efficient deepwater FPSO operations.

Selection of Natural Gas Dehydration Process for Offshore Floating Production Storage and Offloading

Based on the oil and gas component data of an offshore gas field in West Africa, the steady‐state models of the triethylene glycol (TEG) dehydration process and the low‐temperature separation dehydration process are established. The adaptability of two kinds of processes to the disturbance of pressure, temperature, and flow of imported natural gas source is studied, and the sensitivity analysis is carried out. In addition, the investment cost and operating cost of the two types of processes are compared. The low temperature separation dehydration process is more adaptable to the disturbance of inlet gas source than the TEG dehydration process. The former is more expensive to build than the latter, but less expensive to run. The low temperature separation dehydration is preferred as the natural gas dehydration process which is more suitable for floating production storage and offloading.