AbstractPeriodic reassessment of flow assurance risks is a critical topic for greenfield and brownfield projects hoping to ensure an optimal risk management strategy in addition to efficient operations. Greenfield projects must understand the value of flow assurance risk monitoring in order to operate efficiently and reliably throughout the asset life to ensure maximum value is captured. Brownfield operations, in the current market, are continuously looking for methods to reduce cost while maintaining operational excellence. Recently, a comprehensive field optimization of an offshore brownfield application was conducted that focused on a re-evaluation of incumbent wax management strategies for pipelines and flowlines. Balancing pigging schedules with chemical injection is the most common wax mitigation, yet over time drivers for risk management plans can change – specifically for activities like regular pigging of flowlines. The team reviewed extensive laboratory testing of current and potential wax inhibitor chemicals to determine expected performance. The lab results, coupled with operational constraints and recent pigging campaign results, led to a recommendation for a new wax management strategy. Results of the campaign were successful; a dramatic reduction in the wax chemicals required to maintain a manageable wax deposition, and an optimized pigging schedule which resulted in a reduction in operating expenses exceeding $5 million per year. This value creation was a direct result of emphasizing a reassessment of flow assurance risks – specifically waxes – of operating assets. This work will emphasize that flow assurance risks must be continually monitored – to ensure the risk profile has not changed for better or worse, and to identify opportunities to adjust mitigation methods to capture cost savings and/or added value.
Salmin, Davi Costa (Center for Hydrate Research, Colorado School of Mines) | Majid, Ahmad A. A. (Center for Hydrate Research, Colorado School of Mines) | Wells, Jonathan (Center for Hydrate Research, Colorado School of Mines) | Sloan, E. Dendy (Center for Hydrate Research, Colorado School of Mines) | Estanga, Douglas (Chevron Energy Technology Company) | Kusinski, Greg (Chevron Energy Technology Company) | Rivero, Mayela (Total EandP USA) | Gomes, Joseph (DeepStar® Global Offshore Technology Development Program) | Wu, David T. (Department of Chemistry, Colorado School of Mines) | Zerpa, Luis E. (Department of Petroleum Engineering, Colorado School of Mines) | Koh, Carolyn A. (Center for Hydrate Research, Colorado School of Mines)
Gas hydrates can form in subsea oil and gas flowlines, where the depths of seawater and ocean conditions provide the thermodynamic environment for hydrate stability. Hydrates present a major flow assurance problem due to the relatively fast timescales at which they can form, grow/agglomerate, and plug a flowline. The common strategy for preventing hydrate formation uses thermodynamic inhibitors (THIs). However, THIs can be cost prohibitive or impractical as the water content in the flowline and its seawater depth increases. Therefore, there is growing interest in the use of alternative hydrate management strategies, such as the injection of low dosage hydrate inhibitors (LDHIs), which are active at considerably lower concentrations than THIs (e.g. 2 vol.% of LDHI versus 50 vol.% of THI). Anti-agglomerants (AAs) are a type of LDHI that prevent agglomeration and allow hydrates to flow as a slurry in oil and gas subsea flowlines. Before field deployment, AAs are screened and selected using laboratory set-ups, mimicking field conditions, in order to evaluate their performance and determine the effective dosage. Current hydrate agglomeration characterization methods implemented in the industry are non-uniform and qualitative, which can lead to conservative recommendations. In this work, the possibility of quantifying hydrate agglomeration in the presence of AAs is investigated, along with studies of the mechanisms via which AAs may operate. One mineral oil and two crude oils were used with a commercial AA in a high pressure stirred autoclave, equipped with particle imaging probes. Motor current input at a fixed RPM was monitored throughout the experiments and serves as an indicator of relative viscosity of the hydrate slurry. This investigation enabled the development of a comprehensive AA performance evaluation. Hydrate agglomeration was detected and quantified by simultaneous increases in the relative motor current and chord length distribution.
AbstractCharacterization of coastal erosion is paramount to ensure the integrity of any oil and gas facilities. Geophysical surveys are mandatory to build ground models of these particular areas to understand sediment movements and control the risk for the coastal infrastructures safety.Based on past experiences, infield acquisitions and interpretations have fundamentally been improved to acquire recurrent high precision Multi Beam Echo Sounder (MBES) data with the objective of 4D interpretation. Using a recently developed algorithm addressing budget error (Naankeu-Wati et al., 2016), measurement uncertainty of bathymetric soundings has been thoroughly evaluated.Beside the description of innovative acquisition methods, new data interpretation and processing techniques are revealed. For a particular area of interest, the paper shows the essential role of digital geographic tools and particularly Geographical Information Systems (GIS) to interpret 4D hydrographic data. Based on the Bathymetric Position Index (BPI) algorithm, a workflow has been built to automatically map seabed features such as sand waves from time-lapse dataset. Such automatic mapping method affords improving the quality of seabed features comparison through the time by limiting subjectivity of data interpretation.
AbstractThe specific position and variability in width and intensity of the high speed band of currents associated with Loop Current Eddies (LCEs) is of significant interest to offshore operators in the Gulf of Mexico. This is particularly the case when undertaking drilling or offshore development operations and the activities may be located close to or inside the LCE. A study of the Remote Ocean Current Imaging System (ROCIS) data from May 2015 has been undertaken to provide further insight into the variability in intensity and width of the LCE high speed band. We defined the band to be limited by the 0.75 m/s (~1.5 knots) threshold, a typical limit for offshore operations in the Gulf of Mexico. Preliminary results show relevant spatial and temporal variability. The width of the high speed band ranged between ~40–100 km, depending on the state of the LCE, interactions with surrounding eddies and the geopgraphical location of the measurements. Peak speeds ranged from about 1m/s to 1.9 m/s. The shape of the speed profile across the band was also variable. Some cases presented a strong correlation with the Sea Surface Temperature (SST) front of the LCE, where speeds dropped significantly outside of the front. The identification of a few patterns of the high speed band was a promising result within the ongoing effort to derive expected relationships between LCE metrics such as high speed band witdth, intensity, LCE area and strength of the SST front.
AbstractInformation about near-surface currents provided in near-real-time is required in a variety of applications. However, direct measurements of near-surface currents are scarce. In the Gulf of Mexico, the oil industry has been collecting current profiles from deepwater rigs, platforms, and moorings in accordance with BSEE Notices to Lessees (NTLs) since 2005. On the rigs and some platforms, these profiles are usually collected with long-range ADCPs positioned beneath the rig/platform keel, so the measured current profiles typically extend from 70-80m below the surface to as deep as 1000m. Unfortunately, only a few stations are equipped to provide good-quality near surface current data. This study assesses the validity and limitations of some simplistic current profile extrapolation algorithms, including approximation of the near surface current by "slab" flow and profile extrapolation algorithms derived from the shape of the measured subsurface profile or from a generic current profile shape.The analysis is based on data collected by a long-term mooring anchored in approximately 1400m of water in the north central Gulf of Mexico (Green Canyon 782, NDBC ID 42369) and on a year-long data set from a mooring deployed in Keathly Canyon in approximately 1900m of water. The available data include periods of Loop Current Eddies (LCEs), weak cold-core eddies, relatively strong flows characterized by a subsurface current intensification, and high-amplitude inertial oscillations.Velocity profiles were mapped onto fixed depth levels. The subsurface section of the profiles was used to extrapolate mappings from 80-100m to the near-surface. Our analysis shows that, in the winter and in the absence of an LCE, currents in the upper 80m of the water column were quasi-homogeneous. Although current speed near the surface is likely to be higher than current speed at 80m, there is a 90% probability that this difference does not exceed 10cm/s and a slab flow extrapolation is reasonable. When an LCE is present, the accuracy of extrapolation is better if the shape of the near-surface current profile is based on deeper observations. This is also true for the stratified summer water column. The uncertainties of profile extrapolation are quantified for each data set and for each flow regime.
Zhu, Jiayong (Mary Kay O'Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas AandM University,) | Hernandez, Andres (Mary Kay O'Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas AandM University,) | Taneja, Ankita (Mary Kay O'Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas AandM University,) | Zhang, Bin (Mary Kay O'Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas AandM University,) | Mannan, M. Sam (Mary Kay O'Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas AandM University,)
AbstractAs the population grows rapidly in the world and the living standards are getting higher, the energy demand continues to grow. According to the Annual Energy Outlook 2016, the estimated oil and gas consumptions will increase at an annual average rate of 0.2% from 2015 to 2040. To meet the growing energy demand, offshore drilling will continue to explore ultra-deep sea locations and enhance the hydrocarbon recovery in the production processes. The maturing deep-water oil fields face low reservoir pressure. In order to send the hydrocarbons back to the platform and the onshore facilities, overcoming the hydrostatic pressure from the overlaying liquid, which requires sufficient amount of pressure, becomes a significant challenge. Therefore, hydrocarbon boosting system is developed to enhance the transportation to the platform. Additionally, hydrocarbon boosting system can increase the oil recovery factor by 10% to 30%, which is equivalent to transferring additional 50–150 million bbl (fluid barrel) of oil.Perdido is currently the world's second deepest offshore hub in production phase, reaching a water depth of 8000 feet[3, 4]. Drilling at such a depth has tremendous challenges. This calls for the system to work reliably for a long time, otherwise its failure can cause hazards to offshore workers and lead to enormous amount of lost revenue due to downtime and maintenance program. The technology in Perdido project is relatively new, a reliability analysis of hydrocarbon boosting system is crucial for offshore oil production processes in terms of safety and maintenance.This paper aims to review the subsea boosting system at Perdido located in Gulf of Mexico, and to conduct fault tree analysis and dynamic Bayesian network to perform risk assessment of the overall subsea boosting system for reliability analysis. The fault tree and Bayesian network include major components in the boosting system, such as the separators, electrical submersible pumps, umbilical cables and risers. The data for the failure rates of the components in the boosting system are based on the statistics collected in available databases. Additionally, a sensitivity analysis was conducted to investigate the effects of redundancy on reliability using the models developed in this study. The extensive literature reviews identified the functions of the subsea boosting system in the subsea processing as well as its corresponding components. The current research report provides a guideline for making decision on the maintenance of the boosting system and the applications of technology.
AbstractThis paper presents a toolbox for optimizing geotechnical design of subsea foundations. The geotechnical design challenge of subsea shallow foundations is to withstand greater dead and operational loads on soft seabeds without increasing the footprint size or weight. The motivation is to reduce costs associated with installation – for example eliminating the need for a heavy-lift vessel to place foundation units alone if handling limits of pipe-laying vessels are exceeded – whilst providing acceptable in-service reliability. The tools presented focus on prediction of undrained seabed response and are intended for deep water developments on fine grained seabeds, as this scenario presents a significant challenge in terms of minimizing subsea foundation footprints. The toolbox addresses optimization of geotechnical subsea foundation performance through four aspects: (i) optimizing the analysis methodology, (ii) modifying the foundation configuration, (iii) improving the site characterisation data as input to the design, and (iv) altering the basis of design. The research presented derives from a combination of physical model testing in a geotechnical centrifuge, numerical analysis and theoretical modelling. The methods, procedures and processes are presented in terms of design equations, theoretical frameworks or design charts, many of which are freely available as web-based applications. Worked examples throughout the paper demonstrate the efficiencies in terms of footprint area to be realized through adoption of these tools.
AbstractDuring subsea mining operations, minerals are extracted from the seabed, typically at about 2000m depth, and pumped with water through a riser pipe to a surface processing vessel. TechnipFMC, through its subsidiary Technip France, is the lead of a consortium comprising COMEX and DCNS which has been awarded a contract by BPIFrance to develop a pilot subsea mining system. The scope includes the development of a flexible riser. This flexible riser comprises an inner wear protection layer to resist the wear from the slurry, covered by a structure to withstand mechanical loads applied to the flexible during its lifetime.In order to select the most appropriate anti-abrasion material, a large scale bench test has been built to reproduce realistic flow in a piping system and compare wear on different materials; rubber, polyethylene and stainless steels. Complete analysis of the wear patterns has been conducted with the expertise of a laboratory. A statistical comparison between materials is presented. The response to wear, depending on material, geometry and position, is better known. One of the materials shows much better wear resistance than the others and is selected for further development.The next step is the development and qualification of the manufacturing process for the wear protection layer. This process has to be as much as possible compatible with current flexible pipe manufacturing plant. Parameters such as thickness, diameter or length of the layer should be adaptable according to needs. The compatibility with the pipe mechanical structure has to be tested as well. To meet these requirements, existing manufacturing processes are limited. At the time of writing this paper, different manufacturing methods to incorporate this wear protection layer within a continuous industrial flexible production are currently under investigation. Several prototypes will be realized for each manufacturing step. Prototyping is under test and will be presented in a forthcoming presentation.
Sancio, Rodolfo (Geosyntec Consultants, Inc.) | Rao, Pramod (Chevron Energy Technology Company) | Hunt, Christopher (Geosyntec Consultants, Inc.) | Umberg, David (Geosyntec Consultants, Inc.) | Greene, Alexander (Geosyntec Consultants, Inc.) | Misra, Shubhra (Chevron Energy Technology Company)
AbstractThis study presents a simplified framework for the quantification of the probability of seismically induced subaerial and submarine mass movements, an essential input for assessment of tsunami risk. The study incorporates the probability of seismically-induced ground motions developed from a Probabilistic Seismic Hazard Analysis (PSHA) and the probability of landslide triggering given an input ground motion, to calculate the joint probability of seismically-induced mass movement.Potential subaerial and submarine sliding masses of sufficient size to trigger a tsunami were identified through a geomorphological analysis of seafloor bathymetry and topographic relief coupled with available regional geological studies of the area. Typical slide volumes were in the range of 107 and 108 m3, consistent with the volumes noted during historical events.In this study, the probability of triggering a mass movement was defined as the probability of exceeding a threshold seismically-induced displacement value along a defined sliding surface beyond which uncontrolled movement of the slide mass was assumed to occur, leading to the potential development of a tsunami wave. The probability of exceeding the threshold displacement was calculated using the Bray and Travasarou (2007) method for estimating earthquake-induced slope displacements.The study treated uncertainty in the input parameters through the use of probability density functions developed using slope stability back analyses and engineering judgement. Material strength parameters were subsequently updated using Bayes theorem.The results of the study indicated that seismically-induced mass movements with potential for triggering a tsunami wave would have an annual probability lower than 1·10−3. Some of the slide scenarios selected in the study were used by others as input into hydrodynamic analyses for tsunami wave generation and propagation, and subsequently to define design inundation levels and design wave events for marine facilities.
AbstractThe use of elastomers in oil industry extends over a broad range of applications including seals, packing elements, reactive rubber elements, stators, and pads. These applications require a variety of property requirements that may differ for dynamic and static applications or include a need for stimuli-responsive capabilities in certain tools.This research details the effect of nanofillers on elastomer properties for oil and gas components. The effects include enhancement of mechanical properties, wear resistance, thermal conductivity and heat expansion properties. In addition, effects of nanofillers on rapid gas decompression (RGD) resistance, chemical resistance to downhole fluids, and resistance to chemical aging at downhole temperatures were investigated.Advanced rubber nanocomposites formulations, based on Hydrogenated Nitrile Butadiene Rubber (HNBR) elastomers, were designed internally. Their properties were assessed using methods and techniques to qualify elastomers for downhole applications. Mechanical properties of elastomers were evaluated at room temperature and at 325° F, which is a maximum application temperature for HNBR elastomers. RGD testing was conducted according to ISO standards.Results indicated that it is possible to control mechanical properties of elastomers with nanotechnology, including improving the abrasion resistance of the elastomers by more than 100% in dynamic, wear-intensive applications, when compared to commercial compounds typically used in the oil industry. Thermal conductivity was improved by up to 40%, while heat expansion decreased by 30%, providing more versatility for seal design in dynamic applications which are prone to localized heating. In addition, RGD resistance in nanocomposites was examined and compared it to control samples. The industrial scale feasibility for nano-enhanced elastomers was demonstrated by a scale-up study.