Floating Production Storage And Offloading Vessel Research Articles

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.

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.

Plasma catalytic non-oxidative methane conversion to hydrogen and value-added hydrocarbons on zeolite 13X

Non-thermal plasma has unfolded highly efficient, safe to operate novel routes for methane conversion to hydrogen. In this work, methane conversion is performed under atmospheric dielectric barrier discharge (DBD) plasma with and without 13X zeolite-based catalysts i.e., 13X, Ga/13X, Pd/13X, and Pd-Ga/13X. Experimental results indicate that the plasma catalytic process delivered almost twofold higher product yield than the plasma only route. The binary Pd-Ga catalyst possesses highest catalytic performance with about 40 % CH4 conversion at an input flowrate of 5 cm3min−1 and 2 W due to the formation of the Pd-Ga alloy, which acts as catalytic active centre for activating C–H bonds. Product yield can be tailored by the catalyst design where the bimetallic Pd-Ga/13X preferably favours the hydrocarbon formation while H2 is the dominant product obtained over the Pd/13X. The cleavage of C–H bonds of methane molecule over the plasma only route is mainly governed by energetic electrons in the gaseous phase the catalyst activity, and plasma-catalyst synergism play a significant role in the plasma catalysis process. The findings from this work provide significant insights into the methane activation for subsequent optimization of the methane conversion processes operated on floating production, storage, and offloading vessels (FPSOVs). Exploiting untapped offshore natural gas reserves, where conventional pipeline systems are less economical.

Metodología para el análisis estructural de una cubierta principal de un buque FPSO soportando una grúa sobre orugas

Offshore cranes placed on the surface of Floating Production Storage and Offloading (FPSO) vessels affect the structural response of their main decks, which can alter the safe operation of the FPSO vessels. Generally, classification societies rules are used to predict the structural strength of the main deck of FPSO vessels. However, these classification societies rules are limited to estimate the variation of the structural performance of the main deck caused by the operation of offshore cranes under different hydrodynamic conditions. Here, we present a methodology to determine the alteration of the structural behavior of a main deck of FPSO vessel due to different operation conditions of a board offshore crane. This methodology considers the hydrodynamic response for two ultimate limit states: operating and storm conditions from 1000 m water depth in Gulf of Mexico with a return period of 10 and 100 years, respectively. The methodology includes finite element method (FEM) models of the main deck supporting an offshore crane to predict its structural response. The maximum von Mises stress of the main deck does not overcome its maximum permissible stress, which allows a safe operation of the FPSO crane. The proposed methodology can be used to estimate the structural behavior of main decks of FPSO vessels that are modified for supporting offshore cranes, regarding the hydrodynamic response for each FPSO under the operation and extreme conditions in its location. Thus, naval designers could select the better structural modifications of the main decks that decrease their costs of construction and maintenance.

Novel deconvolution method for extreme FPSO vessel hawser tensions during offloading operations

Robust prediction of extreme hawser tensions during Floating Production Storage and Offloading (FPSO) operations is an important safety and reliability concern. Excessive hawser tension may occur during certain environmental conditions, posing an operational risk. The novel deconvolution method is proposed in this paper to provide an accurate extreme value prediction. The predicted return level values produced by the new deconvolution approach are compared with those obtained by the Naess-Gaidai method. On the basis of the suggested approach's overall performance, it is concluded that the innovative deconvolution method may give a more robust and accurate forecast of excessive hawser stress. The stated method may be used effectively at the stage of vessel design while determining appropriate vessel characteristics to reduce possible FPSO hawser stress.

Dynamic characteristics analysis of an in-service SYMS based on long-term field monitoring

The soft yoke mooring system (SYMS), which is widely used in China Bohai Bay and Gulf of Mexico, is the main mooring structure used by floating production storage and offloading (FPSO) in shallow water. Due to its multi-joint connection mode, the SYMS can realize the weathervane effect and ensure that FPSO vessel is at a position with the minimized ocean environmental loading. However, the complexity of ocean environmental loads and the non-linearity of SYMS structures make it difficult to predict the motion behaviors and force states that will be experienced by in-service SYMS, which can affect estimations of structural health status. Dynamic characteristics analysis of in-service SYMS is capable of addressing this complex problem and providing accurate estimations for improving mooring system design and safety. In this paper, a multi-body dynamic model for long-term service SYMS is established. Based on the data from a field monitoring system, the long-term motion characteristics of an in-service SYMS is analyzed. By combining the multi-body dynamic model with monitoring data, the long-term internal force statuses of each hinge joint is calculated. Then, the distribution of hinge joints load and horizontal restoring force are obtained, which provide effective numerical references for service life predictions of future SYMS and safety analysis of in-service SYMS.

Nonsingular fast terminal sliding mode-based robust adaptive structural reliable position-mooring control with uncertainty estimation

This paper addresses a novel robust structural reliable position mooring scheme for a turret-moored floating production storage and offloading (FPSO) vessel subject to system uncertainties, environmental disturbances and unmeasurable velocity. A realistic mooring tension model considering buoys and different cable materials that can improve the capacity of the mooring system is derived. A sigmoid tracking differentiator (STD) is employed as a state observer to estimate the unmeasurable velocity. A structural reliability index is introduced to design a position mooring control law so that an FPSO vessel adequately uses a mooring system on the premise of safety to maintain position in an allowable region. It provides strong robustness and a fast transient response and suppresses chattering by merits of a backstepping method and an integral nonsingular fast terminal sliding mode surface (INFTSMS). An adaptive estimator is proposed to address the required unknown uncertainties and disturbances. Theoretical analysis proves the globally asymptotic stability of the whole system. Finally, comparative simulations on an FPSO vessel are conducted to illustrate the effectiveness and superiority of the proposed position mooring control scheme.

Dynamical Sliding Mode Control for Robust Dynamic Positioning Systems of FPSO Vessels

The conventional proportional derivative (PD) control algorithm with appropriate gain scheduling is generally applied to a dynamic positioning (DP) system. However, finding appropriate gains through gain scheduling makes the DP system more complicated. A sliding-mode control algorithm controls an arbitrary point, such as the turret system on a floating production storage and offloading (FPSO) vessel. This algorithm was developed for DP and can be applied to FPSO vessels considering the uncertainty of the vessel dynamics, unknown time-varying environmental disturbances, and transient performance. To control an arbitrary point on the FPSO vessel using a DP controller, the Jacobian matrix in the kinematic equation is modified to present the arbitrary point in the control. The Lyapunov stability theory is applied in the design of the SM control algorithm to provide robustness to the control system. A time-domain simulation tool was developed to verify the effectiveness of the proposed SM control algorithm. The performance of the control algorithm was evaluated numerically to address its efficacy. The results were compared with those obtained using the conventional PD control algorithm.

Extreme hawser tension assessment for FPSO vessel during offloading operation in Bohai bay

The Floating Production Storage and Offloading Unit (FPSO) is an offshore vessel that produces and stores crude oil prior to tanker transport.Robust prediction of extreme hawser tensions during Floating Production Storage and Offloading (FPSO) operation is an important safety concern. Excessive hawser tension may occur during offloading operations, posing an operational risk. In this paper, AQWA has been used to analyze vessel response due to hydrodynamic wave loads, acting on a specific FPSO vessel under actual sea conditions. Experimental validation of numerical results has been discussed as well.This paper advocates methodology for estimating extreme response statistics, based on simulations (or measurements). The modified ACER (averaged conditional exceedance rate) method is presented in brief detail. Proposed methodology provides an accurate extreme value prediction, utilizing all available data efficiently. In this study the estimated return level values, obtained by ACER method, are compared to the corresponding return level values obtained by Gumbel method. Based on the overall performance of the proposed method, it is concluded that the improved ACER method can provide more robust and accurate prediction of the extreme hawser tension.Data declustering issue has been addressed. Paper highlights ability of ACER method to account for a set of varying sea state probabilities, as required in engineering long term statistical analysis.Described approach may be well used at the vessel design stage, while defining optimal vessel parameters that would minimize potential FPSO hawser tension.

Experimental Determination of Non-Linear Roll Damping of an FPSO Pure Roll Coupled with Liquid Sloshing in Two-Row Tanks

Wave excited roll motion poses danger for moored offshore vessels such as Floating Production Storage and Offloading (FPSO) because they cannot divert to avoid bad weather. Furthermore, slack cargo tanks are almost always present in FPSOs by design. These pose an increased risk of roll instability due to the presence of free surfaces. The most common method of determining roll damping is roll decay tests, yet very few test have been performed with liquid cargo, and most liquid cargo experiments use tanks that span the entire width of the vessel; which is seldom the case for full scale FPSO vessels during normal operations. This paper presents a series of roll decay test carried out on a FPSO model with two two-row-prismatic tanks with different filling levels. To directly investigate the coupling between the liquid sloshing and the vessel motion, without modifying the damping, tests were performed at a constant draft. The equivalent linear roll damping coefficients consisting of linear, quadratic and cubic damping terms are analyzed for each loading condition using four established methods, the Quasi-linear method, Froude Energy method, Averaging method and the Perturbation method. The results show that the cubic damping term is paramount for FPSOs and at low filling levels, were the FPSO is more damped. Recommendations regarding the applicability of the methods, their accuracy and computational effort is given and the effect of the liquid motion on the vessel motion is discussed.

Effects of Topside Structures and Wind Profile on Wind Tunnel Testing of FPSO Vessel Models

This study examined the effects of wind loads on a floating production storage and offloading (FPSO) vessel, focusing in particular on the impact of the turbulent wind profiles, the level of details of the topside structures, and the operation modes of the gantry cranes. A series of wind tunnel tests were performed on the FPSO vessel model, developed with a scale of 1:200. It was observed that the wind loads measured using a low-detail model were often greater than those measured using a high-detail model. The measured wind loads corresponding to the Norwegian Maritime Directorate (NMD) profile with an exponent of 0.14, were approximately 19% greater than those corresponding to the Frøya profile in the entire range of wind directions, because of the slightly higher mean wind speeds of the NMD profile. The wind forces increased by up to 8.6% when the cranes were at operating mode compared to when they were at parking mode. In view of the observations made regarding the detail level of the tested models, a medium-level detail FPSO model can be considered adequate for the wind tunnel testing if a high-detail model is not available.

Selection and Characterization of Packaged FBG Sensors for Offshore Applications.

With the development in the exploitation of maritime resources, the structural health monitoring (SHM) of offshore structures becomes necessary. This study focuses on addressing the practical issues of application of fiber Bragg grating (FBG) sensors for the SHM of offshore structures, in particular an FPSO (floating, production, storage, and offloading unit) vessel. Due to the harsh marine environment and tough working conditions, the FBG sensors must have sufficient protection and good repeatability for long-term monitoring. Thorough research has been conducted to identify the most suitable, commercially available protection packaging for FBG sensors for offshore applications. Further, the performance of the selected FBG sensor packaging is tested under conditions of strong sunlight, heavy rain, and salty water in order to emulate the marine environment. Moreover, the installation method of the packaged FBG sensors is equally important, as it ensures the repeatability and durability of the sensors for their long-term performance. It is shown that the packaged FBG sensors can be installed using resin-based epoxy to maintain the repeatability of the sensor over the long-term. Further, the packaged FBG sensors are installed and tested on a simple FPSO model. The experimental results under full load and ballast draft conditions show that the proposed FBG sensors are competent for the SHM of offshore structures.

Technology Focus: Offshore Facilities (February 2018)

Technology Focus Welcome to the Offshore Facilities feature in this month’s JPT. The three papers featured in this section were selected out of 141 collected covering various elements of offshore-facilities design, construction, installation, operation, and inspection. The first paper covers the design, fabrication, transportation, installation, and startup of a floating production, storage, and offloading (FPSO) vessel in an ultradeepwater location in the Gulf of Mexico. The vessel is connected to production and an export gas pipeline with a disconnectable buoy, which allows the FPSO vessel to sail off location in the event of a hurricane. The paper highlights the design features of the installation and some of the project-execution challenges. The second paper describes a technology-development effort to monitor the mechanical integrity of flexible risers in offshore use through a technique called Monitoring Based on Optical Fiber Attached Directly on Armor Wires, or MODA. This is an interesting approach to assess the integrity of the tensile armor at the top section of flexible risers, and the authors summarize years of work in developing the required hardware and data processing. The final paper covers field work performed to ascertain the functional capacity limits of existing equipment on a deepwater platform in excess of the original nameplate limits. It is fairly typical of the industry that, sometime after process facilities are installed, an opportunity to increase production is presented and the engineer must divine the absolute limits of the equipment. This paper presents a nice narrative of one company’s work to answer this question. I hope you enjoy reading these papers. Recommended additional reading at OnePetro: www.onepetro.org. OTC 27526 General Design of Lean MEG Storing in the Jacket Legs on Liwan Gas Field of South China Sea by Zhi Xia, China National Offshore Oil Corporation, et al. OTC 27719 Fixed Platforms at Aging Oil Fields—Feasibility Study for Reuse to Wind Farms by J.C. Barros, Genesis Oil and Gas, et al. OTC 27742 Enabling Materials and Corrosion Technologies for Optimizing Offshore Developments by Eric J. Wright, ExxonMobil Production Company

Reliability-Based Robust Online Constructive Fuzzy Positioning Control of a Turret-Moored Floating Production Storage and Offloading Vessel

In this paper, a mathematical model for a floating production storage and offloading (FPSO) vessel is introduced at first. Considering the unknown system parameters and environmental disturbances, we proposed a reliability-based robust online constructive fuzzy controller. An online constructive scheme is constructed to ensure the fuzzy system’s fuzzy rules adequate and parsimonious without any prior knowledge about the number of fuzzy rules and the structure of fuzzy system. In addition, the reliability-based matrix is applied to design a new adaptive fuzzy parameter update law which can not only approximate the unknown term containing the non-square reliability-based matrix but also make it possible to analyze the closed-loop system’s stability, which is quite difficult to be analyzed because the reliability-based matrix is non-square. Our proposed online constructive fuzzy controller can not only maintain the FPSO vessel at the desired reliability and heading but also ensure all signals in the closed-loop control system are bounded. Simulations and comparisons with a reliability-based structure-fixed fuzzy controller show our proposed reliability-based online constructive fuzzy controller can achieve the positioning control by using the fuzzy approximator with adequate and parsimonious fuzzy rules.

FPSO Cidade de São Mateus gas explosion – Lessons learned

The explosion accident in February 2015 on the Floating Production, Storage and Offloading (FPSO) unit Cidade de São Mateus in the Brazilian offshore sector was the most severe offshore petroleum accident since the Macondo blowout in the US in 2010. The paper aims to discuss the critical implications for the safety of such installations and to recommend solutions to improve safety of FPSO vessels. The root causes are discussed and compared with those of the Macondo blowout and gas leaks on offshore installations in the Norwegian sector. Most of the root causes of the Cidade de São Mateus accident are similar to those of the Macondo accident and gas leaks on offshore installations in the Norwegian sector. Two root causes of a technical nature, related to aspects of safe design, were completely neglected in the investigation into the Cidade de São Mateus accident. These safety features are implemented on virtually all Norwegian FPSO vessels: first, replacing the use of a pump room with individual deep well, submerged cargo pumps in order to eliminate the pump room explosion hazard and second, locating living quarters in the bow of the vessel to avoid exposure to fire.

Physical modelling of wave scattering around fixed FPSO-shaped bodies

FPSO (Floating Production Storage and Off-loading) vessels used for offshore oil and gas production are operated in deep water, often at locations which experience severe wave loading. This paper reports on laboratory experiments on a series of simplified FPSO-shaped bodies, with the aim of understanding more about the wave-structure interaction, particularly the generation of scattered waves. These tests were carried out in the Ocean Basin at Plymouth University’s COAST Laboratory where the effects on the wave-structure interaction of model length, wave steepness and incident wave direction were investigated. All three models had semi-circular ends, separated by a box section for the 2 longer models. Input waves were based on focused wave groups generated using NewWave with an underlying JONSWAP spectrum. A general phase-based harmonic separation method was applied to separate the linear and higher-harmonic wave components of the free-surface elevation surrounding the bodies, and of relevance to the assessment of wave loads. Close to the bow of the model, the highest amplitude scattered waves are observed with the most compact model, and the third- and fourth-harmonics are significantly larger than the equivalent incident bound harmonic components. At the locations close to the stern, the linear harmonic is found to increase as the model length is decreased, although the nonlinear harmonics are similar for all three tested lengths, and the second- and third-harmonics are strongest with the medium length model. The nonlinear scattered waves increase with increasing wave steepness and a second pulse is evident in the higher-order scattered wave fields. As the incident wave angle between the waves and the long axis of the vessel is increased from 0° (head-on) to 20°, the third- and fourth-harmonic scattered waves reduce on the upstream side. These third- and fourth-harmonic diffracted waves should be considered in assessing wave run-up for offshore structure design, and may be relevant to the excitation of ringing-type structural responses in fixed and taut moored structures.

E&P Notes (August 2016)

E&P Notes (August 2016) A New Reality for Training and Safety Technology Trent Jacobs, JPT Senior Technology Writer If you were at the Offshore Technology Conference in Houston this year you may have noticed the increasingly popular trend of exhibitors using virtual reality (VR) headsets to engage with attendees. The unique visual and immersive qualities that make these devices such great marketing tools are also what some in the oil and gas industry say make them such powerful training tools. VR technology has come a long way since its clunky ancestors were first introduced in the 1990s. Thanks to high-resolution screen technology and powerful gaming engines, the latest generation has been deemed by the techno-experts as ready for prime time. Equally important, VR has become affordable; some of the high-end devices now sell for only a few hundred dollars. This confluence of capability and cost is why Vincent Higgins left his job as a senior-level industry consultant to become the founder and chief executive officer of Optech4D. The 4-year-old Houston-based startup develops custom training programs that recreate oilfield and facility environments inside the VR devices. Ohio Study Tries To Pin a Number to Earthquake Risk Trent Jacobs, JPT Senior Technology Writer Research and development firm Battelle is working on a new induced-seismicity study that aims to help wastewater disposal well operators in Ohio stay on the good side of state regulators. Expected to be completed later this year, the company says the study will be the first to quantify a disposal well’s potential to cause an earthquake. Concern over disposal wells in Ohio was brought to the fore when a series of earthquakes jolted residents of Youngstown, Ohio, in late 2011. A disposal well near downtown was assigned responsibility for the tremors and regulators responded by shuttering that well along with several located nearby— the scenario Battelle is hoping its study can prevent from happening again. Twenty-Year Effort Brings Only Two FPSO Vessels to US GOM Joel Parshall, JPT Features Editor The floating production, storage, and offloading (FPSO) vessel is the world’s most widely used floating production system, with 218 units worldwide installed or on order. Yet, despite the United States offshore industry’s major advance into remote, deepwater projects, there are only two FPSO vessels in the US Gulf of Mexico (GOM). Speaking to the Rice Global Engineering and Construction Forum at Rice University in Houston in June, floating systems consultant Peter Lovie, who has worked on FPSO-related projects for more than 2 decades of a 50-year engineering career, gave a close-up view of the persistent effort to bring FPSO facilities to the US gulf. His talk was titled “2016 and Two FPSOs in the US GOM: The Twenty-Year Saga.” An FPSO vessel produces oil through onboard wells or is connected to subsea producing wells and in some cases receives oil from nearby production facilities. The vessel stores the produced oil in its hull and offloads the oil to tankers that station themselves next to the FPSO vessel, load the oil, and carry it to market. By offloading to tankers, FPSO facilities can avoid the need for oil pipelines connecting to shore and their major installation costs, although some FPSO units do connect with pipelines. Shell Stays Committed to Shale Opportunities Joel Parshall, JPT Features Editor Shell has reaffirmed its commitment to the shale business and views it as a growth opportunity moving into the 2020s, Executive Vice President for Unconventionals Greg Guidry told members of the media in a presentation on 20 June in Houston. Following its recent acquisition of BG Group, Shell has set the strategic priorities for its portfolio in a framework of three time horizons: cash engines of today, growth priorities (2016 and beyond), and future opportunities (2020 and beyond). Guidry noted that shale is in the last group. While some other portfolio choices offer better prospects in the current price environment, shale has “material value upside,” Guidry said. “We have a path to profitability, and we are managing exposure. …. We have the choice to activate shale with the right pricing.” Shell’s current shale production is just less than 300,000 BOE/D.

Subsea Production Optimization in Field BC-10 Offshore Brazil

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 26220, “BC-10: Optimizing Subsea Production,” by N.C. Sleight and N. Oliveira, Shell, prepared for the 2015 Offshore Technology Conference Brasil, Rio de Janeiro, 27–29 October. The paper has not been peer reviewed. The BC-10 asset, located in deep water offshore Brazil, produces heavy oil in the range of 16 to 24 °API. Mudline caisson separators with electrical submersible pumps (ESPs) are used to process fluids from multiple wells and boost them to the receiving floating production, storage, and offloading (FPSO) vessel. There are significant flow-assurance challenges in operating the asset. In this paper, two examples of production optimization for this field will be provided (further examples are available in the complete paper). BC-10 BC-10’s production comes from four fields located in water depths ranging from 1650 to 1920 m and is dependent on artificial lift. This summary focuses on optimizations involving the Ostra field. The subsea architecture that enabled the development of these separate reservoirs consists of multiple drill centers coupled to production manifolds. Manifolds are routed to caisson ESPs. These caisson ESPs will henceforth be referred to as MOBOs (derived from the Portuguese acronym for pump-boosting module). To minimize equipment costs, each field has only two production flowlines routed to the host: one is for production, and the second is for hot-oil displacement and production. In the case of Ostra, a third riser for gas separated subsea is also present. This design reduces the number of risers required. In line with this philosophy, there are only three oil-production trains and one gas separator on the host. Ostra Field Ostra consists of seven producer wells, with production collected by two manifolds and routed through two 8-in. intrafield flowlines to the artificial-lift manifold (ALM), which houses four caisson separator MOBOs. The operating philosophy is to run three units out of four, leaving the fourth unit as a standby in case of MOBO failure. Because the ALM is not located with permanent vertical access, MOBO interventions require the use of a rig capable of pulling the 140-t unit to surface. For this reason, having an installed spare is critical. The production manifolds allow one of two routings per well, which allows a flowline to be aligned to one, two, or more MOBOs; full bypass of the MOBO; and routing of hot oil for MOBO startup and planned shutdown from the surface by a dedicated choke. It is also possible to allow the 4.5-in. hot-oil supply line to be used for production. The 8-in. gas line features a common choke on the ALM to control backpressure on the MOBOs and a surface choke at the FPSO vessel as a second means of control. In practice, to avoid a well trip causing a rapid loss of MOBO pressures (with corresponding well-rate increases), the subsea-gas-line choke is used only in special circumstances, with daily control being performed by use of the topside boarding choke, which allows a much larger gas-storage volume and hence limits rapid pressure transients. The Ostra field has seen good pressure support through the first 5 years of operation because of a strong supporting aquifer, and it currently produces 60,000 to 70,000 B/D gross. Gas disposal was performed through an injection well deeper in the Ostra aquifer while gas export was commissioned.

Fast Production Recovery of a Typhoon-Damaged Oil Field in the South China Sea

Summary The Huizhou oil field is located at the Pearl River mouth in the continental-shelf region of the South China Sea, with an average water depth of approximately 117 m. The oil field's main facilities include eight fixed-jacket platforms, two subsea-production wellheads (HZ32-5 and HZ26-1N), and one floating production, storage, and offloading (FPSO) vessel (Nanhai Faxian). Fig. 1 illustrates the general layout of the field. The peak daily oil production is approximately 70,000 BOPD. In September 2009, after a strong typhoon (Koppu) passed over this oil field, the FPSO vessel's permanent mooring system was seriously damaged. All production risers connected to the FPSO vessel's turret were ruptured, and production was forced to shut down. To resume production in a fast-track manner, several engineering cases were studied. Finally, the concept of using a dynamic-positioning (DP) FPSO vessel to temporarily resume production was selected. Detailed design and operability analysis was performed by the owner of the DP-FPSO vessel, and various flexible pipes and other materials were sourced quickly in local and international markets. The offshore installation took place throughout the harsh winter monsoonal season from November 2009 to February 2010. Finally, the field was brought back into production after 5.5 months of production stoppage. The DP-DPSO system operated for more than 18 months and proved safe and effective. This was world record time for an FPSO vessel operated in DP mode.

Dynamic-Simulation Applications Support Challenging Offshore Operations

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 156146, ’Dynamic-Simulation Applications To Support Challenging Offshore Operations: A Kitan Oil Field Offshore East Timor Case Study,’ Ryosuke Yokote, SPE, and Vanni Donagemma, Eni Australia, and Juan Carlos Mantecon, SPE, SPT Group, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 8-10 October. The paper has not been peer reviewed. The Kitan oil field consists of three subsea intelligent wells. The intelligent completions were modeled in detail using commercial dynamic-simulation software to establish a sound and safe operating procedure for the well cleanup and well test. The simulation results provided the petroleum engineer on the rig with key operational information, such as the time for the oil to arrive at surface and expected pressure at the downhole gauges (DHGs) and upstream of the choke manifold. This enhanced the ability of rigsite supervisors to anticipate well behavior, enabling a significant risk reduction. Introduction The Kitan oil field is approximately 200 km south of the East Timor coast and 500 km offshore of the northern coast of Australia (Fig. 1). The Kitan field development consists of three vertical producing wells, 6-in. production subsea flowlines and risers, 2-in. gas-injection lines, umbilical lines, and a floating production, storage, and offloading (FPSO) vessel. Each well has a designated flow-line and riser tied back to the FPSO vessel (Fig. 2). Fig. 3 shows the intelligent completion for the Kitan development wells. The intelligent completion was de-signed to control flow from two separate zones, upper and lower. Flow from each zone is controlled by flow-control valves (FCVs) that have eight positions (fully opened, fully closed, and six intermediate choke positions). Pressure and temperature for each zone are monitored by three DHGs. The FCVs have a fail-as-is design and stay in the last position should a communications problem be encountered. Because of the remoteness of the location, the functionality of the intelligent completion and the well performance needed to be confirmed with a minimum degree of uncertainty. To establish a sound and safe operating procedure for the well cleanup and well test, commercial dynamic simulation software was used to model the intelligent completion and selected operations. A few different well-cleanup procedures were investigated to predict cleanup time, pressure and temperature at different points of interest, and flow rates on the rig. The simulation results provided valuable information, enabling the petroleum engineer on the rig to predict flow conditions of the well during the operations. Following the successful well-cleanup and well-test campaign, the well models were validated with actual well-cleanup and -test data.