Floating Production, Storage And Offloading System Research Articles

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

Fatigue Analysis of the Oil Offloading Lines in FPSO System under Wave and Current Loads

In this paper, fatigue analysis of oil offloading lines (OOLs) in the floating production storage and offloading (FPSO) catenary anchor leg mooring (CALM) buoy offloading system under wave and current loads in the West Africa Sea area is carried out by the numerical simulation method. The hydrodynamic coupling response is calculated, and fatigue damage is analyzed. Firstly, the numerical model is verified by comparison with the experimental results. Then, according to the environmental statistics in West Africa, the influence of various parameters on the fatigue damage of OOLs is analyzed, including tension characteristics, wave parameters, and structural parameters. Additionally, the effect of current load is studied. Results show that accumulated fatigue damage mainly occurs near the CALM buoy and is mainly caused by the 0° wind wave. Appropriately reducing the cover length of buoyancy material and increasing the wall thickness can reduce fatigue damage. Moreover, the effect of the shuttle tanker can increase the fatigue damage of the OOL near the CALM buoy by about 1.5 times, and the effect of vortex-induced vibration can increase the fatigue damage of the OOL in the middle part by up to 5–10 times.

Drift-off warning limits for dynamically positioned FPSO and Deepwater Artificial Seabed (DAS) coupling system

The new Deepwater Artificial Seabed (DAS) system is developed for dynamically positioned Floating Production, Storage and Offloading (FPSO) vessel, with a focus on important issues of well access and riser design. Nonetheless, FPSO may drift off due to dynamic positioning (DP) system failures and ocean environment loads, and thus loses the capability to maintain position, which poses significant threats to the structural integrity of the DAS system. This study is committed to establishing criteria of drift-off warning limits for dynamically positioned FPSO and DAS coupling system. The fully-coupled dynamic model of the FPSO and DAS coupling system is established. On this basis, a drift-off analysis method is proposed in the determination of drift-off warning limits of FPSO. The effectiveness of the method is verified in the case study of the coupled FPSO-DAS system. Further, the correlative influence factors, consisting of the wave, wind and current conditions, different flexible jumper lengths, FPSO offsets as well as artificial seabed locations, are systematically investigated. The results demonstrate the effectiveness of fully-coupled analysis of the FPSO and DAS system for warning limits determination. The warning limits, consisting of point of disconnection (POD), preparation and initiation point of emergency disconnection sequence (EDS), are mainly located at the near end and far end relative to the artificial seabed due to different failure sites of flexible jumper. The safe area of FPSO is in a “butterfly” shape due to the design characteristics of the DAS system. It is noteworthy that three main aspects of warning limits can be affected by the corelative influence factors, i.e. the angle and radius coordinates of the warning limits as well as the time to failure. The wave height, environmental load direction and flexible jumper length have the most significant effects on the time to failure, the angle and radius coordinates of the warning limits respectively. This study provides a useful tool for the decision-making of DP operations in a drift-off scenario, and contributes to the safety control of the DP operation in the production phase.

Improved condition monitoring for an FPSO system with multiple correlated components

It is expected that a resilient condition monitoring (CM) system can identify the faults of sensors and key components, assess the system risk level based upon multichannel monitoring data, and recover missing real data when complete sensor failure occurs. As for CM of an offshore system, sensors are usually less reliable than the components being monitored. Without CM resilience, the whole system will be vulnerable to accidents and different types of disturbance. This paper provides a statistical and artificial intelligence approach to realizing resilient CM for offshore systems with multiple correlated components. This approach enables identifying sensor faults, damage and degradation of key components through frequency-centered wavelet analysis along with an artificial neural network-based dynamic threshold under different operating environments. More importantly, the proposed method enables the recovery of missing real data based on fusion data from other normal sensors and multivariate Autoregressive Moving Average (ARMA) model. The method is applied to a hawsers’ CM system in a Floating Production, Storage and Offloading (FPSO) oil offloading system. The numerical results illustrate the feasibility and effectiveness of the proposed method in realizing CM resilience for such complex and critical systems.

Production availability analysis of Floating Production Storage and Offloading (FPSO) systems

Floating Production Storage and Offloading (FPSO) systems are currently the popular scheme in offshore oil and gas industry. The profitability of these systems is extremely dependent on their production availabilities. In this article, we report the lessons learned from the assessment of the production availability of a FPSO system. Regarding this study, we used stochastic simulation as the assessment tool because it is naturally suitable for performance evaluation of the production systems. To obtain relevant results, it requires a strong modeling discipline as well as rigorous experimental protocols. By adopting modeling patterns in the production availability analysis, we can model the target systems in a modular way. We propose here to build models by assembling modeling patterns dedicated to production availability studies. We discuss the performed experiments with a special focus on sensitivity analyses. The results by changing the failure rates are validated with those altering the repair rates.

Sloshing in a Horizontal Cylindrical Tank Subjected to Pitching Excitation and Damping Effects by Perforated Plates

Natural gas is relatively clean, and its demand is currently increasing. In most cases, gas fields are located at the bottom of the sea. Therefore, floating production, storage, and offloading (FPSO) systems are now attracting considerable attention. This paper is related to the dynamical design of a FPSO system; in particular, it focuses on the free surface elevation induced by the waves in a horizontal cylindrical and axisymmetric liquid vessel with end caps. In this study, the theory of the wave height and resonant frequency in a horizontal cylinder subjected to pitching via external excitation is developed. Then, a theory taking into account the effect of perforated plates is introduced. A special discussion is made with regard to the number and location of the perforated plates and the effect of a partial opening in a perforated plate on the damping. Finally, the experimental data of resonant wave heights up to the third mode are shown in comparison to the theoretically derived results.

Dynamic analysis of turret-moored FPSO system in freak wave

Freak wave is the common wave which has significant wave height and irregular wave shape, and it is easy to damage offshore structure extremely. The FPSOs (Floating Production Storage and Offloading) suffer from the environment loads, including the freak wave. The freak waves were generated based on the improved phase modulation model, and the coupling model of FPSO-SPM (Single Point Mooring) was established by considering internal-turret FPSO and its mooring system. The dynamic response characteristics of both FPSO and SPM affected by the freak wave were analyzed in the time domain. According to the results, the freak waves generated by original phase modulation model mainly affect the 2nd-order wave loads. However, the freak waves which are generated by random frequencies phase modulation model affect both 1st-order and 2nd-order wave loads on FPSO. What is more, compared with the irregular waves, the dynamic responses of mooring system are larger in the freak waves, but its amplitude lags behind the peak of the freak wave.

ピッチング加振により励起される水平円筒容器内スロッシングと多孔板の減衰効果

Floating Production Storage and Offloading (FPSO) system is now attracting big attention which can develop the natural gas fields under the sea. This paper is related to dynamical design of FPSO system, specially focused on the free surface elevation in the horizontal cylindrical and axisymmetric liquid vessel with end caps induced by the wave. The purposes of this research are to model the sloshing in the horizontal cylindrical container under pitching excitation, and to investigate the damping effect of punching plates. First, the theory on the wave height and the resonant frequency in a horizontal cylinder subjected to pitch external excitation is developed. Then, the theory which is capable of taking account of the damping effect of punching plates installed in the cylindrical vessel is described. Finally, the experimental data of resonant wave height up to the third mode are compared to the theoretically derived results. As a result, we can say that the sloshing theory in a horizontal cylindrical container we built in this paper can demonstrate the wave height response qualitatively and quantitatively especially near the first resonance frequency, and that the damping effect of punching plate can be modeled by using the revised resistance coefficient and the velocity of a flowing fluid.

The Effect of Punching Plates to Suppress the Sloshing in a Gas Liquid Separator

Natural gas is relatively clean and its demand is increasing these days. In most of the case, gas fields are located at the bottom of the sea. Therefore, floating production, storage and offloading (FPSO) system is now attracting big attention. This paper is related to dynamical design of FPSO system, specially focused on the free surface elevation in the horizontal cylindrical and axisymmetric liquid vessel with end caps induced by the wave. In this study, the theory on the wave height and resonant frequency in a horizontal cylinder subjected to longitudinal external excitation is developed. Then, the theory capable of taking account of the effect of punching plates is described. Finally, experimental data of resonant wave height up to 3rd mode are shown in comparison with theoretically derived results.

The process design and simulation for the methanol production on the FPSO (floating production, storage and off-loading) system

A process for methanol production from 100 MM scfd of stranded gas and CO2 is proposed and simulated using a commercial process simulator, PRO/II v.9.1, for a FPSO (floating production, storage, off-loading) system. The process consists of Steam-CO2 Reforming (SCR), methanol synthesis, a Reverse Water-Gas Shift (RWGS) reaction and ancillaries with recycle streams to SCR and RWGS. All reactors were simulated using the Gibbs reactor model. Also, the Plug Flow Reactor (PFR) model with reaction rate equations was used for the methanol reactor and the result was compared to the Gibbs reactor model. To maximize the use of the carbon source in stranded gas and CO2 while avoiding an undesirable increase in process size, the optimum recycle ratios were calculated with a satisfying constraint, a steam-to-carbon ratio≥1 in the SCR. In the proposed Methanol-FPSO process the RWGS reactor can maximize CO2 utilization and case studies were performed to analyze the influence of RWGS.

Offshore oil production units: a new concept of oil production floating hull

The Floating, Production, Storage and Offloading (FPSO) production systems have become a popular choice and may produce fairly appropriate technical and economic benefits for oil fields located far away offshore. In such a condition, underwater pipeline networks would not certainly be adequate. An alternative solution would be the use of large capacity floating reservoir to store the processed oil on board and ship it to shore by smaller shuttle tankers. Thus, some desirable features for the FPSO system include large storage capacity, large deck-areas to accommodate separation plant and good hydrodynamic performance when acted by ocean waves, wind and sea currents. Until very recently, there were worldwide offers of old large tankers approaching life cycle limit. Such a market characteristic helped to increase the number of conversion of old large tankers onto stationary floating production units. The declining of that market associated with the fast increasing of the number of FPSO new projects to be installed mostly in the Southeastern Brazilian Coast, the Western Coast of Africa and, more recently due to relaxation in the legislation, in the Gulf of Mexico, has pressed for changes in the way the next generation of FPSO will be planned. It is clear now that most of the new FPSO hulls will need to be designed and built from scrap. On the other hand, the design of a ship-like hull form to work specifically as a stationary unit raises opportunities to improve its operational performance. There is a wide open field for potential innovations to be incorporated into the design of new FPSO hulls to increase their hydrodynamic performance and to achieve higher efficiency and significant savings derived from using less-expensive equipments and possibly increasing operational time. The motivation of this paper is deeply involved in the perspectives mentioned earlier. It discusses results related to a new particular concept for a FPSO hull. The main focus of the discussion points towards the hydrodynamic behaviour of the new hull in waves and tries to identify its potential effects on costs and operational revenue.

Experimental investigation of an external turret-moored FPSO system by VALM arrangement

This article deals mainly with an experimental study on a typical external turret-moored floating, production, storage and offloading (FPSO) system by a vertical anchor leg mooring (VALM) arrangement in order to investigate the effect of parameters influencing the mooring and hawser line forces and motion response for different loading conditions with different hawser lengths. A 1:100 scale model of 140,000 DWT turret-moored FPSO system was tested for three loading conditions (i.e. 40% DWT, 70% DWT and 100% DWT) with three hawser lengths (i.e. 15%, 20% and 25% of the length of the FPSO model). The tests were conducted in a 2-m wide wave flume at the Department of Ocean Engineering, Indian Institute of Technology Madras, Chennai. The model tests were carried out under regular waves for the wave frequencies ranging from 0.55 to 1.25 Hz in steps of 0.04 Hz at a water depth of 1 m for head sea condition. The motion response was measured using rotary-type potentiometers, and mooring forces were measured using specially fabricated ring-type load cells. The test results of the mooring forces and motion response are analysed and presented with discussion.

FPSO: lessons learned

This article describes about the design of various electrical systems and installation issues of typical FPSOs (Floating, Production, Storage, and Offloading) system and provide some lessons learned. FPSO consists of a vessel or hull and a topsides facility creates many electrical interface issues between the two major parts of the completed vessel. These vessels typically have more extensive electrical systems than the typical fixed platforms. Electrical operating loads may total 40-50 MW or more depending on the vessel configuration. For the purpose of this typical FPSO design, it is assumed that the selected drivers are all electric motors. It is assumed that the total connected load is 70 MW with an operating load of 40 MW. Based on the electrical load requirements, the FPSO has an extensive electrical distribution system. The distribution system for a FPSO are very similar to those of any large distribution system. Lessons learned can only be effective if the are collected on current projects, reviewed for accuracy and sufficient detail to describe the issue, distributed to future project personnel, and incorporated into the new project design. Many of the lessons learned presented in this article are applicable to other types of electrical work and not limited to FPSOs.

A Basic Study on the Wave Induced Responses of a Single Point Mooring System for Medium-Depth Water

The development of ocean oil fields are now going to deeper and smaller oil fields. A FPSO (Floating, Production, Storage and Offloading) system is one of the most economical systems for the production of marginal fields and thus is in use worldwide. For the position keeping of a FPSO system, a single point mooring system is usually employed to economize the operation. However, the conventional single point mooring systems such as a catenary anchor leg mooring (CALM) or a turret mooring (TM) become less economical as the water depth increases because the system becomes heavier in order to sustain the large weight of mooring lines. In this paper, we apply a Counterweight Articulated Mooring (CAM) system, which was originally proposed for a mooring system in ice infested water, as the alternative single point mooring system for a FPSO that may be used in a medium-depth water (500 m).Since a CAM system is mechanically much more complicated than conventional systems, we examine how the behaviours of a CAM system in waves can be predicted theoretically. A computer code is developed based on the constraint matrix method proposed by Langley for the analysis of a floating system composed of a number of structures.Numerical results obtained by the developed code are compared with model test data. And the following conclusions are obtained through the present study.(1) The numerical prediction of wave induced responses of a CAM system gives fairly accurate results.(2) The low frequency responses in irregular waves are governed by the low frequency oscillations of a tanker, which should be predicted while properly accounting for the damping force.(3) The connecting mechanism between a tanker and a yoke should be free rather than be fixed because the stress and the mooring lines' tensions are drastically decreased.

Evolutionary Developments Advancing the Floating Production, Storage, and Offloading Concept

Summary Tanker-based floating production, storage, and offloading (FPSO) systems have been in operation since Aug. 1977, when a single-well FPSO facility was put into production by Shell Espania in the Mediterranean. The overall operational experience with this system at this field is reviewed, with special attention to the wireline work over facilities, which have proved very satisfactory. A subsequent evolutionary step, a FPSO system accommodating multiple wells, necessitated development of a multi bore fluid swivel. A design program for this swivel was initiated in 1978; a prototype was built and full-scale testing finalized in 1980. A summary of the test results is presented. Simultaneously with the multi bore swivel development, detailed engineering for an eight-well FPSO unit was begun. This system includes gas-lift and water-injection capabilities. Provisions for through-flow line (TFL) well work over can be incorporated. The detailed design is reviewed, as well as the latest development whereby the FPSO concept has been adapted to the North Sea environment. Introduction and Background Stationary offshore terminal facilities using former trading tankers were employed by the oil industry as early as 15 years ago. Initially, a tanker was connected by conventional hawsers to a catenary anchor leg mooring, where it served as a combination buffer storage vessel and mooring platform for shuttle tankers. Poor operational experience, low survival characteristics, and high maintenance costs stimulated the development of the single-buoy storage (SBS) system employing rigid arms for permanently mooring the vessel to the buoy. The first terminal of this type became operational in 1973, and it and half a dozen similar terminals have served efficiently for many years. In Aug. 1977 a further step in the evolutionary process was taken with the startup of a tanker-based, rigid-arm single anchor leg storage (SALS) floating production facility at the Castellon field in the Mediterranean off-shore Spain. This system incorporates conventional separation equipment on the vessel for producing from a single subsea-completed well. A second similar facility also producing from a single well was installed in 1980 at the Nilde field in the Sicilian Channel. Recognizing the need for testing and producing independently from two or more wells and injecting into wells, Shell instigated a program in 1978 to develop a high-pressure, multi flow-path swivel for interfacing the weathervaning vessel with the nonrotating buoy or riser. In Aug. 1981 a facility went into operation at the Cadlao field offshore Philippines using this new high-pressure, multi flow-path swivel producing from two subsea-completed wells. A fourth FPSO facility capable of accommodating eight wells went into production at the Tazerka field onshore Tunisia in late 1982. Table 1 provides a recap of these four FPSO facilities. The Floating Unit While a semisubmersible platform is usually in a fixed mooring pattern, a tanker-based floating production facility is normally designed to weathervane, thus introducing the necessity for mechanical and fluid swivels. Both types of swivel must be engineered carefully and constructed to precise specifications. JPT P. 695

An Analysis of Tanker-Based Floating Production Systems for Small Offshore Fields

Summary A historical review of floating production storage and offloading (FPSO) systems for marginal fields is presented. The areas in which such systems are presented. The areas in which such systems are operating, ranges of model tests, and current applicability of mooring systems are reviewed to present capabilities of these concepts. Limitations are reviewed to assess the applicability of these concepts to similar sites.Consideration of processing operations on floating vessels are identified. Particularly, the effects of vessel motion on the processing equipment, gas disposal, and crude offloading are addressed. It will be shown that operations are becoming well understood and routine. Future problem areas and solutions under development are identified. Specific examples are cited and design refinements are noted.While various floating production systems have been in operation for only a few years, their potential for solving the problems of producing small offshore fields and for achieving early production is impressive. Introduction Oil discoveries have been made in offshore areas the world over, which, even at today's crude prices, are considered uneconomical to develop with the conventional fixed platform approach. The type of discovery considered marginal varies according to location, water depth, and recoverable reserves. Several innovations to produce such marginal fields economically have been produce such marginal fields economically have been implemented. Among these are tankers moored on site, taking production through risers from seafloor wells and with processing equipment located on board the tanker. This paper discusses the applicability of such tanker-based floating production systems in two diverse areas-offshore Southeast Asia and the North Sea. The discussion makes use of the results of studies conducted by Marathon Oil Co. over the past 5 years. Historical Development of FPSO Systems Early floating production systems used converted semisubmersible drilling units. Argyll gained prominence as the first floating production system using prominence as the first floating production system using the Transworld 58. ENIEPSA, Spain's national oil company, moored a SEDCO 135 class semisubmersible over a three-well cluster as a production platform in 305 ft (93 m) of water in the Dorado field in the Spanish Mediterranean. Development of several Petrobras fields offshore Brazil, Chevron's Casablanca field offshore Spain, and BP's Buchan in the North Sea also used semisubmersibles.In some cases, the semisubmersibles were selected primarily because they were immediately available. But primarily because they were immediately available. But high day rates, conversion time and costs, and low availability of semisubmersibles have made tankers a more attractive component of floating production systems. A tanker surplus in recent years has made it possible for operators to purchase them at a relatively possible for operators to purchase them at a relatively low cost, thus reducing field development costs significantly by unifying the tanker with subsea production systems. production systems. The use of moored tankers as permanent floating storage at offshore oil fields started in the mid-1960's. However, the first FPSO system went into service in 1977, in Shell Oil Co.'s Castellon field. The development began with production from a single well, with provisions for an increase to three wells. The time from provisions for an increase to three wells. The time from go-ahead to production was only 11 months, primarily because the production system was a variation of several relatively simple systems already in use in the offshore industry. Even though the mooring system was new, design and fabrication were carried out within this limited time. The basic simplicity, combined with relatively low capital and operating costs, permits economical development of offshore fields with small recoverable reserves such as Castellon. The production equipment aboard the Castellon tanker is designed to handle 20,000 B/D (130 m3/h) oil. The associated gas is used as fuel in the ship's boilers, and the excess is disposed of in a pair of incinerators. JPT p. 1871

Effect of Turret Location on the Dynamic Behaviour of an Internal Turret Moored FPSO System

An experimental investigation on the motions and mooring forces of a typical internal turret moored Floating Production Storage and Offloading (FPSO) system under regular sea waves for different loading conditions i.e., 40%DWT, 70%DWT and 100%DWT with different turret locations viz forward, midships and semi- aft positions is reported in this paper. A 1:100 scale model of 140000 DWT turret moored FPSO system was tested in a 2m wide wave flume at a water depth of 1m for the wave frequencies from 0.55Hz to 1.25Hz in steps of 0.04Hz. The motions were measured by rotary type potentiometers and proving ring type load cells were used to measure the mooring forces. From the analysis of the experimental results, it is found that among the three turret locations, the forward turret position is the best suited position for the internal turret moored FPSO system, so as to have favourable and safe working environment. In this turret location, the surge, heave and pitch motions are about 20% to 30% less in comparison with mid ship and semi-aft positions for all loading conditions. Keywords: FPSO system, internal turret, CALM, motions, mooring forces DOI: 10.3329/jname.v3i1.926Journal of Naval Architecture and Marine Engineering 3(2006) 23-37