Floating Production Storage And Offloading Research Articles

Intelligent Completion Enables Zonal Isolation Offshore Malaysia

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 22882, “Advancement of Openhole Gravel Pack and Zonal Isolation With Selective Intelligent Completion in Deepwater Malaysia,” by Elvy Samuel, SPE, Noppanan Nopsiri, and Lee Chan Fong, PTTEP, et al. The paper has not been peer reviewed. Copyright 2023 International Petroleum Technology Conference. _ As fields mature, drilling and completion design and execution for infill development become more challenging. In a deepwater environment, one strategy is to target several reservoir packages in a single wellbore. This technique frequently presents technical challenges, however, because penetrating different zones requires active reservoir management, an allowance for zonal isolation, and an adequate response to potential crossflow. The complete paper presents a completion strategy implemented in an intelligent well completed in the Malaysian deepwater Block K. Introduction The SNP Field is 125 km offshore Sabah in approximately 1350–1400 m water depth. The field crosses the boundary between Block K and Block G, approximately 15 km from the Kikeh floating production, storage, and offloading (FPSO) facility. The field commenced Phase 1 in 2011 with the completion of nine oil producers as openhole gravel packs (OHGPs) and five water injectors with expandable sand screens at the sandface. Phase 2 development, partially covered in the complete paper, commenced in the third quarter of 2021 with three standard oil producers and one smart producer well. All SNP Phase 2 wells were completed as OHGPs targeting various sand reservoirs in a common pressure regime. The well discussed in the complete paper addressed subsurface uncertainties related to depth and the pressure differential between the upper zone (UZ) and the lower zone (LZ) and the isolation requirements of the middle zone (MZ) by implementing an intelligent completion architecture with an OHGP with zonal isolation on the sandface. The flow diversion between the producer zones would be achieved through the deployment of an intermediate completion coupled with an intelligent completion architecture in the upper completion. The well was placed on production in the first quarter of 2022 to the Kikeh FPSO, achieving the targeted rates solids-free. Gravel-Pack Design In this field, the fracture pressure window is marginal, suggesting that a conventional OHGP approach would be challenging. Adding to this complexity is the zonal-isolation requirement. To achieve the objective of complete openhole (OH) coverage and to enable zonal isolation simultaneously, shunt-tube technology was identified as critical. The selection of shunt-tube technology allows the following achievements: - Premature screenout mitigation, because the technique is a proven system that enables the slurry to bypass any restriction in the OH/screen annulus - Zonal-isolation capabilities by combining shunted sand screens and OH mechanical packers with selective shunt-tube isolation capabilities - Application of diverter valves, crucial in fields with marginal fracture pressure windows

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.

Improvement energy performance for GHG mitigation - a case of FPSO vessel platform in Oil & Gas offshore production

This study offers an in-depth review of specific facets of the oil and gas industry, emphasizing the role of Floating Production, Storage, and Offloading (FPSO) vessels. It delves into diverse topics, highlighting potential opportunities, a solid research methodology for emissions quantification, and the pivotal challenge of reducing GHG emissions. Among the multitude of opportunities analyzed within the industry's value chain, the upstream sector - encompassing both exploration and production of oil and natural gas - receives considerable focus. This sector can be further divided into key segments characterized by high energy consumption and consequent significant emissions. Notably, the combustion of natural gas for power generation stands out, contributing a substantial 68% of CO2 emissions at related facilities. This process is a primary target for mitigation and energy efficiency enhancements. The intricate interplay between energy generation and CO2 emissions stands at the forefront of current research, emphasizing the need for improving vessel energy efficiency. This paper employs a case-based methodology, evaluating the effectiveness of energy efficiency measures within an FPSO setting and their resulting impact on GHG emissions. Central to this inquiry is a detailed examination of the FPSO Fluminense, strategically located within Brazil's Campos Basin, with the study meticulously examining the relationship between advancements in energy efficiency and emission reductions. While translating these insights into practical applications poses challenges, the momentum generated by rigorous research, combined with policy recommendations addressing GHG emissions in the oil sector, can indeed chart a path toward a more robust, sustainable, and integrated energy future.

Experimental Study on Adaptive Backstepping Synchronous following Control and Thrust Allocation for a Dynamic Positioning Vessel

Cargo transfer vessels (CTVs) are designed to transfer cargo from a floating production storage and offloading (FPSO) unit into conventional tankers. The dynamic positioning system allows the CTV to maintain a safe position relative to the FPSO unit using a flexible cargo transmission pipe, and the CTV tows the tanker during operating conditions. The operation mode can be considered a synchronization tracking control problem. In this paper, a synchronization control strategy is presented based on the virtual leader–follower configuration and an adaptive backstepping control method. The position and heading of the following vessel are proven to be able to globally exponentially converge to the virtual ship by the contraction theorem. Then, the optimization problem of the desired thrust command from the controller is solved through an improved firefly algorithm, which fully considers the physical characteristics of the azimuth thruster and the thrust forbidden zone caused by hydrodynamic interference. To validate the effectiveness of the presented synchronous following strategy and thrust allocation algorithm, a scale model experiment is carried out under a sea state of 4 in a seakeeping basin. The experimental results show that the CTV can effectively maintain a safe distance of 100 m with a maximum deviation of 3.78 m and an average deviation of only 0.99 m in the wave heading 180°, which effectively verifies that the control strategy proposed in this paper can achieve safe and cooperative operation between the CTV and the FPSO unit. To verify the advantages of the SAF algorithm in the thrust allocation, the SQP algorithm and PSO algorithm are used to compare the experimental results. The SAF algorithm outperforms the SQP and PSO algorithms in longitudinal and lateral forces, with the R-squared (R2) values of 0.9996 (yaw moment), 0.9878 (sway force), and 0.9596 (surge force) for the actual thrusts and control commands in the wave heading 180°. The experimental results can provide technical support to improve the safe operation of CTVs.

IMPACT OF OCCUPATIONAL NOISE ON THE CIRCULATORY SYSTEM OF WORKERS IN A TYPICAL FLOATING PRODUCTION VESSEL

This study investigates the possible impacts of occupational noise exposure on the circulatory system of workers in a typical floating, production, storage and offloading (FPSO) unit in the Niger Delta Offshore work environment in Nigeria. The VLIKE iiVL6708 digital sound level meter was used to measure noise levels at 2-hour interval overianii8-houriiworkday. OMRON-10iiSeries iiBP7450 Upper Arm Blood Pressure monitor was used to measure arterial blood pressure i(systolic and diastolic) and pulse rate of work before and after exposure for 8-hour workday.

Mechanical characterization procedure of HMPE fiber for offshore mooring in deep waters

For several offshore installations, especially those for exploration of offshore resources, such as Floating Production Storage and Offloading (FPSO), the stability of subsea pipelines and exploration risers are closely related to the mooring system. High performance polymeric fibers have been used in recent decades for offshore mooring, more recently polyester has been challenged by advancement in ultra-deep waters due to its considerable elongation. A candidate fiber for lower elongation mooring systems is high modulus polyethylene (HMPE). The work describes mechanical characterization procedures in high modulus polyethylene fibers envisioning the possibility of offshore mooring systems made entirely with HMPE, which allow deeper water depths, as well as stability to the pipelines. As a result, the fiber is suitable for mechanical strength and linear tenacity. It still shows good performance in abrasion resistance, and loss of inelastic portions in cyclic loads. However, the behavior in creep, due to its slightly high strain rates, restricts its use, but recent fibers known as "Low creep" can be studied, allowing complete mooring systems made with HMPE.

Numerical simulation of heat transfer performance of spiral wound heat exchanger under sloshing condition

LNG floating production storage and offloading (FPSO) unit is a new type of floating production unit developed for offshore natural gas fields. It performs the functions of natural gas extraction, pretreatment, liquefaction, and storage. In this study, the heat transfer characteristics of a spiral-wound heat exchanger were studied using numerical simulations, which provides a basis for equipment selection and structural optimization of spiral-wound heat exchangers. The main research contents and conclusions are as follows. Under land-based simulation conditions, the heat transfer coefficient of the shell side of the spiral-wound heat exchanger decreases with an increase in the winding angle of the heat exchange tube, decreases with an increase in the spacing of the heat exchange tube, and increases with an increase in the outer diameter of the heat exchange tube. When the winding angle increased from 5° to 8°, the heat transfer coefficient decreased by 6.70%. The heat transfer coefficient of the shell side decreased by 13.21% when the heat exchange tube spacing increased from 14 to 17 mm. The heat transfer coefficient of the shell side increased by 22.89% when the outer diameter of the heat exchange tube increased from 9 to 12 mm. When the sloshing angle is constant, the heat transfer coefficient of the spiral-wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient decreases as the sloshing angle increases. When the sloshing angle was less than 3°, the sloshing promoted heat transfer on the shell side. When the sloshing angle was higher than 7°, the heat transfer effect of the shell side deteriorated considerably, which weakened the heat transfer performance of the heat exchanger. When the sloshing period is constant, the heat transfer coefficient of the wound heat exchanger decreases with an increase in the winding angle and spacing of the heat exchange tubes, and increases with an increase in the outer diameter of the heat exchange tubes. When the structural parameters of the heat exchanger are constant, the heat transfer coefficient increases with sloshing period. When the sloshing period was greater than 15 s, the influence of sloshing on the heat transfer on the shell side of the heat exchanger was relatively weak.

Stiffened Plate Analysis by Considering Follow-up Plates in the Effect of One-Way Axial Load on FPSO Vessels

Floating Production Storage and Offloading (FPSO) is the portable offshore structure. The material configuration used is the most important aspect in the FPSO structure design criteria. Plates and Stiffened and plates experience local buckling due to the external load when the hull girder collapsed. The objective of the present study is to analyze the stiffened plates taking the attached plate thickness into consideration on the FPSO in term of plate deformation and deflection located of the bottom area under tension and compression stages. In this study the attached plating thickness is varied according to FPSO data and BKI Rule. The stiffened plate elements located at the bottom are modelled by Tee-Bar element. The simply supported condition is applied to the model and the Non-Linier Finite Element Method (NLFEM) is used for the analysis. The result obtained by NLFEM shows that under tension and compression the stiffened plate of model of the thickened plate of the FPSO, the deflection are 1.75 mm and -1.75 mm, respectively. While for model of corrugated plates with BKI minimum intervening plate thickness the deflection are 1.8 mm and -1.8 mm under tension and compression, respectively.

Optimization of subsea production control system layout considering hydraulic fluid pressure loss

Historically, layout optimization of the Subsea Production Control System (SPCS) has primarily emphasized equipment construction costs, frequently overlooking the influence of the seabed's three-dimensional terrain on hydraulic pressure loss during power distribution. Such neglect can escalate maintenance costs throughout the oil and gas field's lifespan. This article presents an advanced SPCS layout optimization approach that addresses hydraulic pressure loss. A multi-objective optimization model, accounting for the intricate seabed three-dimensional terrain and obstacles, was developed for the multi-level Star-Tree structured SPCS. This model integrates parameters such as construction costs, pressure loss, and pipeline routes. By merging the strengths of NSGA-II (Non-dominated Sorting Genetic Algorithm II) and Lazy Theta*, a novel hybrid algorithm has been proposed. This algorithm is adapted at determining the optimal position for the Subsea Distribution Unit (SDU), refining the pipeline connectivity topology, and minimizing pressure loss, thereby identifying superior laying paths. In a case study featuring an SPCS with 20 Subsea Control Modules (SCM) and one Floating Production Storage and Offloading (FPSO) unit, the method's efficacy in reducing hydraulic pressure loss was demonstrated in simulation results. The findings of this research hold promise as a pivotal decision-making instrument during the SPCS design phase, providing profound theoretical insights for layout design.

A System to Detect Oilwell Anomalies Using Deep Learning and Decision Diagram Dual Approach

Summary Detecting unexpected events is a field of interest in oil and gas companies to improve operational safety and reduce costs associated with nonproductive time (NPT) and failure repair. This work presents a system for real-time monitoring of unwanted events using the production sensor data from oil wells. It uses a combination of long short-term memory (LSTM) autoencoder and a rule-based analytic approach to perform the detection of anomalies from sensor data. Initial studies are conducted to determine the behavior and correlations of pressure and temperature values for the most common combinations of well valve states. The proposed methodology uses pressure and temperature sensor data, from which a decision diagram (DD) classifies the well status, and this response is applied to the training of neural networks devoted to anomaly detection. Data sets related to several operations in wells located at different oil fields are used to train and validate the dual approach presented. The combination of the two techniques enables the deep neural network to evolve constantly through the normal data collected by the analytical method. The developed system exhibits high accuracy, with true positive detection rates exceeding 90% in the early stages of anomalies identified in both simulated and actual well production scenarios. It was implemented in more than 20 floating production, storage, and offloading (FPSO) vessels, monitoring more than 250 production/injection subsea wells, and can be applied both in real-time operation and in testing scenarios.

Subsea Multilateral Oil Producer Evaluated With Acoustic and Production-Logging Tools

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210299, “A Subsea Multilateral Oil Producer, Completed With AICD Sand Screens and Selective Inflow Valves, Is Evaluated by Combined Acoustic and Production-Logging Tools, Identifying the Sand-Producing Branch and a Tubing Leak in a Single Operation,” by Duncan Troup, SPE, Archer; Tim Griffin, SPE, Three60Energy; and Minh Pham, Aker BP, et al. The paper has not been peer reviewed. _ A horizontally completed subsea multilateral well exhibited unexpected sand production and a tubing leak, leading to the well being shut in. The complete paper discusses the novel tools and techniques used to localize the tubing leak, identify the bore responsible for sand production, and provide relative sand quantification at differing flow rates. Well Background and History The well was drilled and completed as a subsea producer to be tied back to an existing floating production, storage, and offloading (FPSO) vessel by means of a subsea flowline. After drilling of the first lateral, the decision was taken not to complete it. A second lateral was then drilled and completed. The main and secondary bores were drilled into different zones of the reservoir. Both lower completions used standalone sand screens, autonomous inflow-control-device nozzles, and swell packers set in open hole. Each of the lower completions was fitted with a hydraulically actuated inflow control valve (ICV) for managing production flow from the reservoir zones, providing the ability to produce each leg independently or commingle them. The upper completion is equipped with two gas lift valves (GLV) to provide artificial lift, a chemical injection mandrel, and a surface-controlled subsea safety valve (SCSSV). After approximately 6 months of flowing the well, water cut was seen to increase and a series of “popping” events occurred in which productivity increased markedly for short periods. Significant quantities of sand soon began to accumulate in the FPSO topside facilities. Approximately 1.5 years after startup, well productivity decreased sharply over a few months while the water cut continued to increase. As the productivity continued to decline, the leak rates exhibited by the SCSSV and one GLV fell outside the acceptable criteria. The pressure responses indicated a high leak rate. The well was shut in pending diagnostic logging and repair of the leak. Sand-Source Investigation The subsea wellhead of this well was fitted with an acoustic sand detector, but this had only indicated minor amounts of solids in the flowstream over the producing lifetime of the well. An extensive investigation concluded that the makeup of the collected sand was most likely to have originated in the case study well and that the amounts involved were likely to have been a contributing factor in the loss of well integrity. Because the well was producing from two different branches, a probability existed that only one of these was suffering from sand production. The well completion was designed to allow independent control of the branches by use of ICVs, so an intervention to assess the status of each of the branches with respect to water and sand production was planned, with the additional objective of diagnosing the well-integrity failure.

Optimization of system of Oscillating Water Columns to mitigate pitch response of FPSO platforms submitted to head waves

This work presents a novel method for reducing the pitch response of FPSO (Floating, Production, Storage and Offloading) platforms submitted to head waves. The method is based on installing a couple of moonpools, modeled as opened Oscillating Water Columns (OWC), on the vessel. According to detailed literature review, the effects of the vortex shedding can be represented through a nonlinear damping factor, which is proportional to the relative motion between the vessel and the water column within the moonpool.Optimization solvers are adopted to design the moonpools, using potential theory to calculate the vessel response with an iterative procedure to properly account for the nonlinear viscous damping factor related to the vortex shedding.The use of metaheuristic optimization method is discussed, with the choice of Particle Swarm Optimization. Different mono-objective functions are explored by weighing the minimization of the peak response and the area underneath the response curve. The importance of imposing restrictions on the modified vessels to avoid increasing heave motion is presented, using the penalty function also by weighing the peak response and the area. Results show the effectiveness of the procedures proposed in the study and indicate the possibility of expanding to implement it in other applications.

Review of Offshore Chemical Flooding Field Applications and Key Lessons Learned

Summary This paper presents an overview of both current advancements and field applications of offshore chemical flooding technologies. Along with offshore oilfield development strategies that require the maximization of oil production in a short development cycle, chemical flooding can become a potential avenue to accelerate oil production in secondary oil recovery mode. This makes it different from onshore chemical flooding processes that mostly focus on enhanced oil recovery in mature or maturing reservoirs. The advancements in offshore chemical flooding field applications are reviewed and analyzed. By summarizing offshore application cases, the presented analysis also assesses the chemical formulations applied or studied and injection/production facilities required in offshore environments. The main technical challenges are also discussed for scaling up the applications on offshore platforms or floating production storage and offloading (FPSO) systems. The chemical flooding technologies reviewed include polymer flooding, surfactant-polymer (SP) flooding, and alkaline-surfactant-polymer (ASP) flooding. By assessing the technology readiness level of these technologies, this study presents their perspectives and practical relevance for offshore chemical flooding applications. It has been long realized that chemical flooding, especially polymer flooding, can improve oil recovery in offshore oil fields. The applications in Bohai Bay (China), Dalia (Angola), and Captain (North Sea) provide the know-how workflows for offshore polymer flooding from laboratory to full-field applications. It is feasible to implement offshore polymer injection either on a platform or in an FPSO system. It is recommended to implement polymer flooding at an early stage of reservoir development to maximize the investment in offshore facilities. By tuning the chemistry of polymer products, they can present very good compatibility with seawaters. Therefore, choosing a proper polymer is no longer a big issue for offshore polymer flooding. There are also some interesting findings reported on the development of novel surfactant chemistries for offshore applications. The outcome from a number of small-scale trials, including the single-well chemical tracer tests on surfactant, alkaline-surfactant (AS), and SP in offshore Malaysia, Abu Dhabi, Qatar, and South China Sea, provided valuable insights for the feasibility of chemical flooding in offshore environments. However, the technology readiness levels of surfactant-based chemical flooding processes are still low, partially due to their complex interactions with subsurface fluids and the lack of interest in producing residual oil from matured offshore reservoirs. Based on the lessons learned from offshore applications, it can be concluded that several major challenges still need to be overcome in terms of large well spacing, reservoir voidage, produced fluid treatment, and high operational expense to successfully scale up surfactant-based chemical flooding processes for offshore applications. Key Terms and Phrases offshore chemical flooding; polymer flooding; surfactant-based chemical flooding; offshore application cases; lessons learned

Analysis of FPSO Motion Response under Different Wave Spectra

A variety of floating structures at sea play a vital role in the exploitation and utilization of marine resources. The study about interactions between waves and structures is necessary for the impact of the harsh marine environment on the motion and service life of structures. Currently, most studies about the seakeeping of structures are based on simplified regular waves. Because the regular waves do not truly restore the actual wave conditions at sea, the simulation of irregular waves has great practical importance to the study of interactions between waves and structures. Based on the potential flow theory and high-order boundary element method (HOBEM), a Fortran code is developed in this paper and named as SWBI (Solver for Wave–Body Interactions). This program consists of the following two parts: a time–domain numerical model about interactions between waves and 3D structures is based on weakly nonlinear method, and a numerical model about simulation of the nonlinear regular waves, the long-crested irregular waves, and the short-crested irregular waves. This Fortran code is used to simulate the motion of Floating Production Storage and Offloading (FPSO) under three different ocean wave spectra (including ITTC two-parameters spectrum, JONSWAP spectrum and the most likely spectral form of Ochi-Hubble) and found that: To a certain extent, the difference in the motion of FPSO under different wave spectra have a connection with different type of wave, sea conditions and incident angle. The difference in roll of FPSO is quite significant in short-crested irregular waves. The range of FPOS’s roll under the JONSWAP spectrum is the largest when the incident angle is 30°, and range of FPOS’s roll under the most likely spectral form of Ochi-Hubble is the largest when the incident angle is 90°.

Woodside offshore dry deluge testing

Wet deluge testing of firewater systems is considered a recognised contributing factor to accelerated corrosion on offshore facilities. Spraying sensitive equipment and structures with sea water is not only disruptive to the facility, it can also cause process upsets and is labour intensive with set-up and subsequent fresh water washdown. While ensuring the performance of this safety-critical system is vital through regular testing, adopting new methods with less adverse impacts is of high importance. Dry deluge testing using a propylene glycol-based vapour as an alternate testing medium has been adopted on offshore facilities in the US, Dutch, Danish and UK sectors, significantly reducing the frequency of wet testing. A generator is used to produce smoke-like vapour, which is then pumped into the system piping through existing test connection points while the system remains online. The vapour migrates throughout the distribution piping, ultimately exiting the deluge nozzles to visually identify any blockages. This method of testing will reduce costs to businesses, not only for deluge testing itself, but more importantly from an asset fabric maintenance perspective. Woodside Energy successfully carried out the first offshore dry deluge testing in Australia on the Okha FPSO (floating production, storage and offloading) in 2021. The testing covered varied deluge and foam system arrangements with different nozzle types. This paper details the dry deluge tests conducted on Okha, the results gathered, main operational and implementation concerns of the testing and recommendations on further collaboration and improvements for adopting this test method across the Australian oil and gas industry.

Harmonic structure of the nonlinear force on a fixed ship-shaped floating production, storage and offloading vessel under dispersive phase-focused wave groups

This paper presents a numerical investigation on the harmonic structure of hydrodynamic forces on a fixed and simplified representative floating production, storage and offloading (FPSO) vessel hull under dispersive phase-focused wave groups. The high-fidelity numerical model utilizes the two-phase flow solver in the open-source toolbox OpenFOAM. A series of cases were computed using the numerical model, where the effects of wave steepness, bow diameter, and length of the FPSO are investigated. It is found that given an FPSO under different wave steepness, the non-dimensional inline force exhibits remarkable similarity in terms of the temporal development. The harmonic structure of the inline force is only weakly dependent on the steepness of the incident wave group and the bow diameter, but strongly dependent on the FPSO length. When k p L = 2.27, where L is the length of the FPSO and kp is the wave number at peak frequency, the incident wave group is diffracted significantly by the FPSO. The entire wave–structure interaction process is largely linear, where transfer between different harmonics is rarely seen. However, when kpL is further reduced to 0.57, globally the disturbance of the FPSO on the far field incident wave group is reduced, but locally a strongly nonlinear flow occurs at the rear of the FPSO, where severe run-up occurs at the downstream stagnation point. Higher-order harmonics of inline forces are excited, and the interaction process becomes much more nonlinear.

Decarbonization of energy supply to offshore oil & gas production with post-combustion capture: A simulation-based techno-economic analysis

Low-carbon-emissions FPSO (Floating, Production, Storage, and Offloading) designs are developed and compared, using process simulation in HYSYS, and an original economic analysis approach. FPSO units with power-intensive operations (e.g., fields with high gas-to-oil ratio) are the focus of the study. Three designs are evaluated: Case A considers a floating natural-gas-combined-cycle power unit with post-combustion CCS (Carbon Capture and Storage) connected to an existing FPSO. Case B.1 retrofits a CCS unit downstream of a conventional FPSO with simple-cycle power generation. B.2 adds a more efficient combined cycle to B.1. The removed CO2 is injected for enhanced oil recovery. Marginal abatement cost is investigated for oil prices of 60/80/100 USD/bbloil and recovery of 0.0/1.5/3.0 bbloil/tCO2 injected. The added weights to topsides are 4,326t (A), 2,762t (B.1) and 3,445t (B.2). CO2 intensity (kgCO2/boe) is reduced from 6.92 in the conventional design to 0.74 (A-B.2) and 0.92 (B.1). The marginal abatement cost of B.1 and B.2 are alike, approaching zero at 1.5 bbloil/tCO2 oil recovery. Taking technical retrofitting challenges aside, Case B.1 is the most cost-effective alternative. Cases A and B.2 have a slightly better environmental performance than B.1, but B.2 presents a superior economic performance and lower operational risks compared to A.