bluuebunny/crossref_metadata_2025 huggingface dataset:
The Future State of Completions for the Lower Tertiary in the Gulf of Mexico
Authors: Techentien Bruce , Ingram Stephen , Grossmann Andreas
Published: April 2016

The Wilcox formation in the Lower Tertiary is an interesting and challenging development. The industry is currently seeking ways to increase efficiencies, increase production, and optimize performance of this reservoir. This paper discusses the current status in generation V single-trip multizone completions as well as future prospects to predict industry options for the formation.

This paper seeks to spur the industry into thinking about the future cost benefits and management of change necessary to design solutions for this unique development. Regarding Lower Tertiary wells, operators sometimes assume the wells are similar to the Wilcox formation in South Texas. However, studies indicate these wells should be treated like other Gulf of Mexico (GOM) wells, and they do require sand control. Is the industry willing to take these technical development risks? If unique solutions are proposed, what preparations are necessary, and how should planning proceed?

There are unique solutions that operators can apply to the deepwater GOM as well as alternative solutions, processes, and procedures developed for land applications that can be adapted to the deepwater GOM. Land production has adopted the horizontal approach for efficiencies, but is this the correct approach for deep water? The multilateral approach is an interesting option that has been applied in other offshore environments, but is this a concept adaptable for the Lower Tertiary? How can monitoring and control be applied to these two concepts from land applications? How do operators take industry knowledge and apply it to the unique offshore environment of deepwater and subsea completions?

The ultimate goal of this paper is to examine these questions and initiate the thought process of how the industry can optimize the returns from the Lower Tertiary by increasing production and recoverable reserves through technology and reservoir management.
Comparison of Fatigue Calculations Methods for Structural Integrity Assessment of Offshore Structures
Authors: Sahasakkul Watsamon , Arablouei Amir , Sari Ali
Published: April 2016

The objective of this study is to evaluate fatigue damage and fatigue life of offshore structures using different fatigue calculation methods. Of interest in this study is to identify an efficient method for fatigue calculation of the offshore structures by comparing the Simplified approach, the Spectral approach, and the Fracture Mechanics approach provided in API [3], DNV [5], ISO [7], and ABS [2] guidelines/standards. Fatigue calculations use advanced application tools including SACS [10] and Abaqus [11] coupled with in-house tools. An efficient path in providing safety in structural integrity management is presented in this paper, which can minimize the cost and improve time management for a variety of projects.
The Successful Development and Installation of a New Single-Trip Multizone Completion System Developed for the Deepwater Gulf of Mexico Lower Tertiary Formation
Authors: Grigsby Tommy , Jannise Ricki , Goodman Archie , Techentien Bruce , Schexnailder Michael , Navaira Guy
Published: April 2016

Development of the Wilcox stacked oil sands in the Lower Tertiary fields in the Gulf of Mexico (GOM) requires zonal stimulation; however, when the decision was made to produce this formation, the stacked sand-control systems currently available would have been cost prohibitive. Thus, a special team was commissioned to develop a single-trip multizone completion system to address the challenges of producing this ultradeepwater GOM field.

This paper chronicles the development, qualification, and installation of a new one-trip high-rate fracture system that meets the needs of cased-hole installations in the Lower Tertiary formations with well depths reaching 28,000 ft TVD, as well as in cased-hole shallow-depth wells in the Asia Pacific area.

A dedicated development team began tool-system development in January 2007. The first systems integration test (SIT) was conducted in December 2007 after only 11 months. The successful SIT led to the assignment of three land wells by a major international oil company to prove out the multizone system. After two successful installations, the third installation was eliminated, because the multizone system was classified as operationally ready.

Drilling issues lead to the plugging and abandonment of the planned inaugural ultradeepwater installation. The operational moratorium in the GOM in 2010 also changed the original target wells. The first commercial cased-hole installation was run in the Asia Pacific area in a shallow-depth well environment using water-pack treatments. Subsequently, multiple ultradeepwater installations have been performed to date.

Lessons learned from the SIT process and from the initial installations that included the ultradeepwater Lower Tertiary fields are presented.
New LRFD-Based Design Criteria for Mobile Offshore Units and Floating Production Installations
Authors: Yu Qing , Tan Pao-Lin , Lo Tzu-Wei , Chow Weng-Yin (Jan)
Published: April 2016

A new set of Load and Resistance Factor Design (LRFD) based structural design criteria that is compatible to the existing Working Stress Design (WSD) criteria in the ABS classification rules for mobile offshore units (MOUs) and floating production installations (FPIs) has recently been developed. This paper presents an overview of the new LRFD-based structural design criteria with a primary focus on their applications, the load combinations, and the partial safety factors. The paper also presents a summary of the verification case studies for typical MOUs and FPIs. The case study results provide a direct comparison between the new LRFD-based design criteria and the current ABS WSD criteria, which have been used for designing numerous MOUs and FPIs. The verification case studies demonstrate the suitability of the LRFD-based design criteria. The new LRFD-based design criteria are expected to provide an alternative method to designers, owners and operators, who can choose their preferred design approach that meets the local national requirements and better utilizes their experience and resources.
Elastomers for High Pressure Low Temperature HPLT Sealing
Authors: Chen Xuming , Bartos John , Salem Hamid , Zonoz Ray
Published: April 2016

This study demonstrates the characteristics of elastomers with excellent sealing performance at both low and high temperatures, as required by subsea wellheads and blowout preventers (BOP). Elastomers with excellent rapid-gas-decompression (RGD) resistance and high temperature sealing normally have limited low temperature sealing performance due to their high modulus characteristics. It is, therefore, challenging to identify elastomers with RGD resistance that have both high and low temperature sealing performance. This study investigates the glass transition temperature (Tg) and high pressure compression stress relaxation behavior of various elastomers at low temperatures, and presents their influence on low temperature sealing performance under test conditions of static as well as cycling pressure/temperature. Additionally, the effect of high pressure N2 test gas on elastomer sealing performance was investigated.
CFD Predictions of FLNG BOG Including the Influence of Filling, Offloading, and Vessel Motion
Authors: Yu Kai , Ge Zhongfu , Korpus Richard
Published: April 2016

The accurate assessment of boil-off gas rate is essential for the design of FLNGs and LNG carriers. Unfortunately, existing engineering methods used to estimate these rates are fairly primitive. Current methods can account for conductive heat transfer but the details of convective mixing are not included. Since convective mixing can be the larger of the two, better methods are needed to account for the impact of LNG movement due to filling, vessel motions, and off-loading. Modern CFD methods are able to account for all these effects, and this paper describes the development of one such technique using the commercial software package StarCCM+. The approach builds a 3D CFD model for one entire tank, including insulation, filling and discharge pipes, gas vents, and (if necessary) cofferdam areas and internal tank structure. Hydrodynamics, thermodynamics, heat transfer through the insulation and phase change are all computed simultaneously. Results are included for two distinct cases: one depicting a filling operation and one simulating the effect of vessel motions. In each case, 3D, time-dependent distributions of temperature, fluid velocity, pressure, and LNG volume fraction are presented. In cases where gas pressure increases beyond a preset limit, time histories of vented gas property and flow rate are given at the vent. Videos are available that demonstrate the complexities of spatial and temporal variations. Accuracy is demonstrated by comparing to known model problems for which validation data exists, and best practices are provided to assist other practitioners start their own applications.
Comparative Study of Different Erosion Model Predictions for Single-Phase and Multiphase Flow Conditions
Authors: Parsi Mazdak , Kara Mustafa , Sharma Partha , McLaury Brenton S. , Shirazi Siamack A.
Published: April 2016

There are various equations and models for assessing erosion for both single phase and multiphase flow scenarios. Consequently, this study was performed to shed light on the issue of which models provide better predictions. For the single phase situation (air-sand flow), Computational Fluid Dynamics (CFD) erosion modeling in a direct impact geometry was conducted, and the performance of four different erosion equations was scrutinized. On the other hand, for the multiphase flow scenario, churn/annular multiphase flow regimes, that can be highly erosive when sand is present within the piping system, were selected to examine the accuracy of six different widely-used multiphase flow erosion models. For both cases, the modeling results were compared to available experimental data.

For the first part of the study, ANSYS FLUENT 16.1 was used to perform CFD-based erosion modeling including flow modeling, particle tracking, and erosion calculation. For the other part, several codes were employed to investigate six empirical/mechanistic erosion models including: 1D churn model, 2D mixture model, multiphase model, annular model, DNV GL model, and Salama model. The University of Tulsa SPPS software and the DNV GL Erosion Tool were used for this part. Furthermore, the Salama model was coded.

It was revealed that under air-sand flow conditions, Arabnejad et al. (2015a) mechanistic model provided the best results (15% error compared to experimental data). For the multiphase flow part of the study, it was found that regardless of particle size, the multiphase erosion model underpredicts all erosion data, and the 1D churn, Salama and 2D mixture erosion models significantly overpredicted the experimental data. Moreover, the annular and DNV GL models provided the best predictions among all six models.

A literature survey reveals that there is a limited number of comparative studies for erosion prediction models. This study, therefore, should be of interest to a broad readership including but not limited to erosion, corrosion, multiphase flow, and flow assurance.
BOP System Reliability Planning and Testing
Authors: Zou Tong , Holmes J. , Shah Viral
Published: April 2016

Reliability-Availability-Maintainability (R-A-M) is one of the most important sets of functional requirements for a Blowout Preventer (BOP) system. Requirements derived from R-A-M are key for the success of pressure control and the BOP system. Using the design for reliability (DfR) process and system engineering approach, the team established feasible reliability and maintainability requirements based on field performance of similar equipment, performed risk analysis to identify necessary mitigations, and allocated system requirements to the various subsystems. Consequently, the team created system models to assess system reliability as subsystem data is captured. Where necessary, subsystem reliability demonstration tests were executed. The test and analysis results from the components are integrated, via reliability modeling approaches, to the system-level. These results will demonstrate the mean time between maintenance and drilling availability for the BOP system, as well as the probability to perform on-demand for each critical BOP function. The test and analysis results also help identify the weakest link in the system to proactively drive design improvement, and determine the optimal maintenance strategy. The methodology presented in this paper is not only essential to ensure the R-A-M of the BOP system under design, but can be applied to other DfR work.
The World's First Deepwater Multiphase Pumping Application above 100bar ?P, Technological Risks and Mitigations
Authors: Bibet Pierre-Jean , Huet Nicolas , Âsmul Vidar
Published: April 2016

The Girassol Resources Initiatives (GirRI) is a major brownfield deepwater project, which seeks to optimize the Girassol FPSO production. It is also the third subsea boosting project being developed offshore Angola by Total, the operator, and OneSubsea, the contractor. High boost multiphase pumps (MPPs), with an operating ?P of 110 bar at 53% GVF are deployed subsea on two existing deepwater oil production loops to enhance the Rosa field reserves and production, a world's first for the oil and gas industry.

Before using a new pump at the leading edge of technology, an extensive qualification program and a series of stringent acceptance tests were waranted to demonstrate the soundness of the design.

Developing the first high boost MPP application also required revisiting the subsea pumping station architecture to mitigate as many of the risks as possible associated with pumping a multiphase fluid at high pressure.

This paper details how the Project Team addressed the risks associated with multiphase pumping above 100 bar ?P, and how the contractor met all the requirements specified by the operator to build a robust one design-fits-all pumping solution.
Mitigating Gas in Riser Rapid Unloading for Deepwater Dual Gradient Well Control
Authors: Yuan Zhaoguang , Morrell Dan , Sonnemann Paul , Leach Colin
Published: April 2016

In deepwater dual gradient wells, if gas comes into the riser, a rapid unloading event may occur if removal of the gas is not carried out properly. Oil based muds present an even greater challenge when compared to water based muds to avoid gas in riser events, because the gas dissolves in the mud and may not be detected until it breaks out inside riser near the surface.

A study using a dynamic multiphase flow software simulated a rapid unloading event and determined the gas fraction in the riser annulus and the effect on riser fluid levels. New procedures, such as shut-in the riser or proactively applying surface pressure were simulated to evaluate effectiveness of riser-top equipment to mitigate risks of rapid riser unloading. The effects of gas volume, and mud type (water vs. oil based mud), on water hammer and riser top pressure during the shut-in were analyzed using a simulated case with a riser in 8,000 ft of sea water.

The analysis shows there is no significant pressure increase at the moment of rapid unloading in a shut-in well. The simulation results reliability is verified using a field test conducted in 1,200 ft sea water. The simulation results show it is possible to safely manage gas-in-riser events for large gas fractions using available managed pressure drilling and riser gas-handling equipment.

It should be possible to safely and efficiently manage events involving even relatively large gas influxes in risers by use of new proposed procedures, which mitigate the rapid unloading and can help industry develop new guidelines for deepwater drilling operations.
Subsea All Electric Technology: Enabling Next Generation Field Developments
Authors: Winther-Larssen E. , Massie D. , Eriksson K. G.
Published: April 2016

This paper will show that utilizing all-electric standardized and configurable hardware, together with appropriate software building blocks, an all-electric Subsea Production System will be a cost competitive alternative to electro-hydraulic systems.

By integrating automotive and telecom competence with subsea expertise, it has been possible to implement a rigorous design-to-cost mindset in the development of the various all-electric system building blocks.

All-electric hardware and software will give large benefits both in terms of reduced CAPEX and OPEX (in addition to improved health and safety as well as increased functionality) derived also from applying subsea and downhole all-electric technology solutions on a wider scale.

For all electric systems, the following general cost benefits have been estimated:

CAPEX

OPEX

HSE, (Safety and Environment in particular)

Increased functionality

Reliability

Flexibility

Electric actuation, sensing, integrated power management and control offer the promise of smaller, lighter and more cost effective subsea production systems. They also offer the potential for more precise measurement, control and maintenance monitoring over time over their hydraulic counterparts, which enables planned maintenance of equipment, with significant benefits in terms of reduced OPEX.
Introducing Holistic Approach for the Design and Operation of FLNG Development
Authors: Kheireddine Houssein , Chen Derek , Timms Jennifer
Published: April 2016

As is the case with any new technology, floating LNG includes uncertainties and unforeseen risks. With the methodology proposed in this paper, some of these risks may be identified and mitigated in design and operations. Specifically, the methodology will quantitatively and holistically assess the entire system's performance over the design life. The results of such a study improve stakeholder confidence in the proposed design, ensure that the limited space on the vessel is used effectively for production, prepare the system for operations by identifying and addressing potential resourcing and operational issues, and project the effects of gas well depletion on the system performance.

DNV GL will use TARO software to execute the proposed methodology. With this software, it is possible to evaluate equipment in terms of its contribution to planned and unplanned downtime. Repair delays, maintenance crew size and availability, spare parts availability, flaring limitations, weather conditions, and limited LNG/LPG/condensate working volumes which impact production can also be captured in the model. On an entire-system level, TARO can model the dynamic relationship between the processing facility, storage/loading system and shipping schedule. The results of TARO would be used to minimize inventory level and optimize LNG carrier sizes and numbers. Depending on the type of negotiated LNG sales demand contract, demurrage cost can also be quantified.

The results generated serve as a feed to cost-benefit analyses used to determine whether or not the additional cost associated with the proposed design/operations modification is justified against the incremental increase in production. This will provide managers with decision support, not only from an efficiency standpoint, but also from an economic standpoint.
Geophysical Reservoir Characterization and Monitoring at Brazilian Pre-Salt Oil Fields
Authors: Johann Paulo Roberto Schroeder , Monteiro Rubens Caldeira
Published: April 2016

In 2006, the Brazilian pre-salt oil field province was discovered from a pioneer well at Lula oil field. The province is characterized by carbonate reservoirs, microbial and coquina rocks, buried at a depth that surpasses 5,000 m, distributed in the Santos and Campos sedimentary basins, located at the east Brazilian coast. During the past ten years, upon the discovery of several oil fields and their respective productions, which now exceeds 1,000,000 boepd, there has been major progress in the application of new geophysical technologies with greater impact on the reservoir characterization and monitoring, in both exploratory and development production phases.

This paper will present such progress made by the application of geophysical technologies in the acquisition, processing and interpretation stages oriented to the reservoir characterization and monitoring.

More specifically, in regards to the reservoir characterization area this paper will address the new technologies that influenced the definition of the external and internal geometries of carbonate reservoirs, both from stratigraphic and structural point of view.

New methods of seismic characterization of reservoirs, from the elastic inversion, the extraction of geometric attributes and the use of new technologies to reveal geological fractures corridors will be therefore detailed. Another major challenge described will be the implementation of 4D seismic technology for monitoring the behavior of fluid motion and pressure variation in the Brazilian pre-salt carbonate reservoirs.

As for the reservoir monitoring, this paper will show the progress of the pioneer project of 4D seismic monitoring of microbial carbonates through NODES technology in an ultra deepwater area where the development of production applies the alternating injection of water and gas (WAG).

Finally, we will present remaining geosciences challenges and the opportunities for the use of new technologies that can help us in the reservoir characterization and monitoring of these Brazilian pre-salt carbonate reservoirs.
Design Considerations of Subsea HIPPS Architectures Evaluating Functional Safety and Reliability for HPHT Application
Authors: Malave Angel , Gronstedt Jens
Published: April 2016

Objectives/Scope: Subsea high-integrity pressure protection systems (HIPPS) have become a standard feature in numerous subsea fields around the globe. Subsea HIPPS' reduced pipeline costs are proven to shorten delivery times for pipelines by decreasing their pressure rating in green field projects or by including high-pressure wells into brownfield projects without modifying rating in existing pipelines.

New frontiers for HIPPS are created by high-pressure (7.5 to 20 kpi) and high-temperature (100° to 200°C) applications, as current pressure transmitters, valves and actuators reach their limits. Furthermore, each HIPPS challenges engineering to achieve a compromise between functional safety and reliability - especially in demanding HPHT fields. These opposing characteristics within the protection systems cannot be treated separately but have to be evaluated as two closely related aspects of engineering.

This paper covers the balancing of these two engineering areas by using the numerical evaluation of probability of failure on demand (PFD) and failure rate (FR) figures. The evaluation is based on safety integrity level 3 (SIL 3) low-demand HIPPS, for which relevant subcomponents and system failure behaviours were simulated. Different HIPPS architectures were applied based on various process sensors, logic solver and final element quantities and their arrangements. The objective of this paper is to investigate the potential improvement of HIPPS design with low PFD and high mean time to failure (MTTF).

Methods, Procedures, Process: Reliability methodologies are based on reliability block diagrams in accordance to IEC 61508 and ISO 12489. Current state of the art safety equipment generic databases for subsea equipment are used to reflect the sub-system's section of HIPPS loops with regards to their functional safety and reliability capabilities.

Results, Observations, Conclusions: This paper indicates optimal and suboptimal architectural configurations and their tradeoff regarding functional safety and reliability.
Integrated Power Management is the Key to Reliable Renewable Energy in Remote and Off-Grid Applications
Authors: O'Brien Jayne , Tomlinson James
Published: April 2016

Renewable energy sources, such as solar and wind, are attractive energy sources for the Oil & Gas industry, particularly in remote or off-shore applications. The challenge with these energy sources is that they cannot provide a steady, reliable source of energy on their own. To date, most systems rely on large battery banks or oversized generators to supplement the renewable power. The shortcomings include cost, size, weight and maintenance.

Tetra West Technology has conducted a series of technical studies in order to optimize the integration of renewable energy, back-up power generation, and battery storage. These design studies have resulted in development of a system which maximizes the use of the renewable energy source, minimizing the required battery capacity, and further minimizes operating time and size of the back-up generator.

Advanced integrated power management techniques can achieve 35% savings for a given solar application while assuring 99.999% power supply reliability, including remote land or off-shore locations. Integrated power management systems can be sized for a wide range of power requirements, allowing maximum benefit of renewable power – particularly when managing motor start or short term surge power requirements.

These advances in power system integration are scalable and can be applied to a wide range of applications – from small remote pumping stations to large off-shore facilities. Employing components proven for these environments, an optimized integrated power management system provides a high degree of both system and power delivery reliability. With proper system sizing, these integrated systems can assure low cost and high reliability energy in a wide range of applications.
Strength and Fatigue Assessment of Extended Bilge Keels for FPSO/FLNG
Authors: Kim Sungeun Peter , Petricic Martin , Xie Geng , Wu Guangyu , Seah Robert
Published: April 2016

This paper presents advanced analysis procedures for the strength and fatigue assessment of FPSO bilge keels which are developed under the joint development project (JDP) between ABS and Chevron. For enhanced performance of FPSO/FLNG units in harsh environments, large bilge keels with extended depth are often considered in real designs. Damage cases of the bilge keels have been reported, but industry guidelines on the structural design of the bilge keels are very limited due to the nonlinearity of hydrodynamic loads on the bilge keels. In this paper, a first-principles approach is proposed by introducing the Computational Fluid Dynamics (CFD) based hydrodynamic loads into the Dynamic Loading Approach (DLA) based full ship FE structural analysis for the strength and fatigue assessment of bilge keels. The design loads at a 10-8 probability level are considered for strength assessment and the long-term Weibull distributions of stress range are considered for the simplified fatigue assessment at critical locations.
Slamming Load Prediction Using Overset CFD Methods
Authors: Shen Zhirong , Hsieh Yi-Fang , Ge Zhongfu , Korpus Richard , Huan James
Published: April 2016

Slamming pressures provide one of the most important load sets for the design and classification of ships and offshore structures. These loads are highly localized and nonlinear, and therefore difficult to predict. Computational Fluid Dynamics (CFD) is a viable tool for their estimation, but validation must be demonstrated before its use is acceptable in standard practice. This paper addresses validation of slamming pressure predictions for two popular software packages: OpenFOAM and Star-CCM+. Both 2D and 3D tests are undertaken, and the predicted pressures compared to available validation-quality experimental data. The 2D cases involve tests of generic ship sections dropped from different heights. Three-dimensional simulations utilize a scale model 10K TEU container ship at different speeds operating over a range of incident wave conditions. The dynamic overset grid technique is applied to handle large-amplitude motions. Good agreement between CFD and experimental data is achieved in the bow area, along the bottom plating, and in the topsides flare area. A few of the comparisons (e.g. on the flat deck) highlight areas where additional work is justified. Overall, the results demonstrate the accuracy, flexibility and robustness of CFD performed using the overset grid technique.
The Development and Field Introduction of a Subsea Wellhead Connector for Intervention Operations
Authors: Canny Steven A , Foubister Graeme
Published: April 2016

Subsea operations in general, attract significant expense; from the requirement of a multi-disciplinary team, through to the logistics of equipment and service conveyance in a harsh offshore enviroment. Costs are typically recovered through the reservoir production potential value over a number of years – this is not the case in abandonment operations. Upon cessation of production, the cost of abandonment is absorbed as a liability; as such the focus on cost efficiency is stringent and acute. It is however an area where the adoption of new and novel technology, allied to an alternative approach to service vessel selected and campaign structure, can achieve significant cost savings.

This paper describes the development of a subsea wellhead connector intended for use in well abandonment operations, in rigless decommissioning projects conducted in the UK Continental Shelf. It presents one of alternative rigless approaches to field decommissioning, and through collaboration with operators, cost effective equipment is developed reactively to meet their operational requirements. Deviating from a Jack up/MODU based rig campaign to a Monohull based campaign has shown savings can be achieved through a significant reduction in vessel day rates and personnel costs. The requirement of rigless abandonment technologies and equipment is growing as the market adopts rigless abandonment; as such, collaboration is required to align equipment with operators requirements.

The development of the Subsea Wellhead Connector (SWC) was undertaken and delivered in 29 days, with design, application, fabrication, and commissioning expedited to meet an aggressive operations schedule. A dedicated project team allied to robust internal engineering and testing programs, facilitated the delivery and leveraged over twenty years of lessons learned in subsea operations. The SWC is intended for Intervention and well abandonment operations, including: conveyance for mechanical and abrasive cutting, wellbore communication and testing, subsea tree (XT) installation, and well barrier verification, and wellhead retrieval.

The SWC has now undertaken five campaigns in the first six months since its market entry, and displayed that collaboration and the pooling of creative talent, can provide tangible and discernible benefits to the stakeholders involved.
A Coast Guard Perspective: Evaluation of Continued Service Proposals for Floating Offshore Facilities
Authors: Phillips Tracy , Martyn David
Published: April 2016

The views expressed herein are those of the authors and are not to be construed as official or reflecting the views of the Commandant or of the U. S. Coast Guard.

As floating offshore facilities approach the end of their design service lives, operators are working with the Coast Guard and the Bureau of Safety and Environmental Enforcement (BSEE) to gain approval for continued service. The two agencies work together to review these proposals; the Coast Guard evaluates the hull and associated safety systems, while BSEE evaluates the mooring and production systems. This paper presents a Coast Guard perspective, beginning with a review of Coast Guard structural examination records for the Gulf of Mexico. The results of this review are presented and analyzed for trends. The authors accept that a well maintained facility, with a thoroughly documented service history and inspection record, is a good candidate for life extension. This paper then discusses In Service Inspection Programs (ISIP) and Structural Integrity Management (SIM) programs, both of which provide a method of ensuring that floating offshore facilities are safely operated and maintained. These programs lay the foundation for discussions regarding continued service. This paper also discusses various information that can be used by the Coast Guard to evaluate a proposal for continued service, including, but not limited to, historical data, baseline surveys, cathodic protection, coatings, corrosion, maintenance records, inspection results, fatigue data and weight changes. While the evaluations of continued service proposals are handled on a case-by-case basis, the same basic principles apply to all floating offshore facilities which are being considered for continued service.
Challenges in Material Selection and its Qualification for use in HPHT Environment for Drilling Equipment
Authors: Meruva Satya , Patel Harish N. , Gonzalez Alexander , Cridland Marcus
Published: April 2016

High-pressure high-temperature (HPHT) well bore conditions present a unique challenge for the equipment and materials exposed to them. The subsea environment further exacerbates the HPHT challenge due to corrosive seawater, weight restrictions, variable external loads, and lack of immediate accessibility. From a materials perspective, a comprehensive understanding of the material physical properties and robust analysis of the potential failure mechanisms active in HPHT and subsea conditions is necessary for satisfactory equipment design validation and verification. This paper will discuss the challenges in HPHT materials selection and qualification, and the process by which acceptable design practices, safety margins, and prototype testing will be established.

Environmentally assisted cracking and fatigue cracks are the dominant failure mechanisms in HPHT designs. Due to the elevated pressure and temperature, elastic-plastic material design models are applied. Dependable physical performance under extreme conditions is the primary objective. Metallic materials are generally subject to tensile tests at elevated temperatures, fracture toughness tests in simulated environments (including the drilling, production, and saltwater with corrosion protection environments). Fatigue crack growth testing is performed in order to determine the relevant material properties in anticipated environments. Elastomeric and metallic seals in HPHT design must be operable for across wide temperature range in corrosive environments and must be tested accordingly. Presently, standards specific to HPHT drilling equipment designs are still under development, and designs are evaluated from first principles due to the lack of field data. Functional production, inspection, and quality standards must also be developed. ABS is currently addressing these challenges at a design level with OEMs and is assisting in contributing to safety by verifying and validating that designs for HPHT equipment will follow the guidelines per all applicable API and ASME codes and standards. This paper will discuss the challenges associated with the material selection.

This paper aims to help to establish a baseline for on-going efforts in standardizing the certification process of HPHT materials and their manufacturing processes for global applications. The knowledge gained by the development projects will be instrumental for the classification society certifying materials for HPHT equipment, to develop certification requirements aimed at improving safety on deep-water drilling units and preventing pollution of the environment.
Lessons Learned From a Comprehensive Review of Integration and Installation Phases of Gulf of Mexico Floating Production Systems
Authors: D'Souza Richard , Basu Shiladitya , Khurana Sandeep
Published: April 2016

Beginning in 1986, with the Placid Oil GC 29 development using a converted drilling semisubmersible in 460 m of water, the Gulf of Mexico (GOM) has been the incubator of deepwater Floating Production System (FPS) innovation. In the following 30 years over fifty FPSs that included Tension Leg Platforms (TLPs), Spar platforms (Spars) and Semisubmersible platforms (Semisubs), were sanctioned . Deepwater frontiers have been extended to over 2,900 m in that span. Many technical and commercial challenges have been managed and overcome in doing so. In the wake of the recent collapse in oil and gas prices and the specter of a prolonged period of low hydrocarbon prices, the industry is confronting perhaps its most formidable challenge in developing new deepwater fields in the GOM that require a host facility.

Historically, all too frequent project execution cost and schedule overruns were masked by rising oil prices. In many instances, the topside to hull integration, platform installation and hook-up to mooring and riser systems and commissioning (Integration and Installation Phase) have been the root cause of overruns as they are high risk, high consequence activities with little float for schedule recovery. In the current low oil price environment there is little margin for error for Integration and Installation (I&I) miscues that rapidly erode project value.

The authors have reviewed the critical I&I phase performance of thirty-three (33) TLP, Spar and Semisub platforms in the GOM and substantiated the review based on either first-hand experience, public domain information or in discussions with project team leaderships. The objective is to provide performance benchmarks, observations and recommendations for future FPS developments in the GOM to help avoid repetition of costly missteps and delays and incorporate lessons from those projects that have been well executed.
Multiple-Point Geostatistical Lithofacies Simulation of Fluvial Sand-Rich De-Positional Environment: A Case Study from Zubair Formation/South Rumaila Oil Field
Authors: Al-Mudhafar Watheq J.
Published: April 2016

Modelling accurate geological structure is an important step in reservoir simulation. The common pixel-based algorithms are incapable of generation the most realistic geospatial patterns. However, multiple-point Facies Geostatistics (MPFG) procedure is more efficient to capture complex geological structures as it mainly based on utilizing the training images that reflect geological architecture. In this paper, we present a detailed MPFG of fluvial sand-rich depositional environment in South Rumaila Oil Field in Iraq.

The fluvial depositional system was created through a 2D user-defined training image that was sampled to create a surface map. Then, neural networks algorithm was adopted to train the surface map in order to create the discrete template for pattern generation of 3D Facies distribution along with the 3D Grid Construction. The resulted training image represents a numerical geological model that contains three-dimensional information about a geological heterogeneity and structure. The facies pattern was then considered for 3D Lithofacies modelling conditioning to upscaled discrete facies distribution for 20 wells in the reservoir.

Based on core data analysis, three lithofacies have been modeled and predicted for all 20 wells that were distributed main at the reservoir crest. The lithofacies are Sand, Shaly Sand, and Shale. The training image body and channels were pointed to the three aforementioned facies and it replaced the variogram to create the 3D Facies system. The resulted integrated model through multiple-point statistics has much more reasonable facies architecture than indicator simulation as it is clearly noticeable how sand channels are distributed with continuous direction towards the sea shoreface. To check how validate our model and capture the true depositional environment, many realizations were generated based on leave-one-out cross-validation technique. The sand channels continuity was achieved through spatial posterior probability of Lithofacies distribution that were incorporated in MPGF approach as 3D trend model. However, including the geometrical trend models of thickness or depth has no effect on the channels continuity. The spatial posterior probability trends were modeled from the predicted probability distributions of Lithofacies that have been created by Kernel Support Vector Machine for all 20 wells in the formation.

The resulted reasonable MPGF model was considered for core permeability and log porosity distribution given each facies through Gaussian simulation. In reservoir simulation, the MPGF model has led to fast reaching the minimum error of history production matching. That reflects how is efficient considering multiple-point statistics to reconstruct complex geological structures.
Gas Hydrate Formation & Interactions for Water Continuous & Partially Dispersed Systems
Authors: Vijayamohan P. , Majid AAA , Chaudhari P. , Sloan E. D. , Sum A. K. , Dellecase E. , Volk M. , Koh C. A.
Published: April 2016

A major flow assurance concern is to mitigate the safety risks associated with hydrate plug formation and to provide cost effective flow assurance strategies for mature fields by extending subsea tiebacks. One major challenge for the flow assurance community is the fundamental understanding of the hydrate formation and plugging under different multiphase flow conditions. Such understanding will only lead to better hydrate management guidelines to effectively mitigate the safety risks associated with hydrates, but could also potentially reduce the operating costs by providing improved inhibitor injection strategies. The manner in which the hydrates interact/interfere with multiphase flow can be significantly different for water continuous, oil continuous, and partially dispersed systems. The latter is defined as a system containing oil/gas/water, where the water is present both as free water and partially dispersed in the oil phase (e.g., entrained water in the oil). Efforts were made to study the interaction between hydrates and multiphase flow. Controlled amounts of hydrates were formed and their effect on the pump pressure drop was studied systematically. This paper presents the experimental results and analyses of these experiments. Lessons resulting from this work could provide valuable insight with regard to the behavior of hydrates in multiphase flow, and hence could help improve operating company production strategies to mitigate the risks associated with hydrate plugs in complex multiphase systems.
Comparison of Hydraulic Power Sources for Subsea BOP's
Authors: Bedrossian Nazareth , Welker Joseph , Coppedge Charles , Hernandez Jorge
Published: April 2016

This paper compares the performance, nominal and robust, of hydraulic power sources that can be used to operate subsea BOPs. The comparison is made between conventional gas pressure accumulators and a dormant, on-demand power system. A brief introduction is provided to PYRO-Accumulator, developed by Bastion Technologies which uses solid propellant to pressurize hydraulic fluid in a self-contained device which is dormant until it is activated to meet hydraulic pressure demand. Simulation and field test results are used to compare the hydraulic fluid capacity needed to provide usable hydraulic fluid volume and pressure to actuate subsea BOP's.
A New Look at Seafloor Venting: Natural Gas Hydrate Derivatives
Authors: Barnard A. , Sager W. W. , Snow J. E. , Max M. D.
Published: April 2016

Natural leaks of multiphase hydrocarbons from the seafloor are widespread. Characterizing the temporal and spatial variability of these emissions provides baselines for comparison to the magnitude of anthropogenic leaks. Determining leakage rates will be important to our understanding the sustainable implementation of subsea infrastructure and the relative contribution of natural sources to global budgets. Multibeam echo soundings from cruise AT21-02 were used to define a region with several ~600 to 900 m tall gas plumes in the water column directly above cratered hummocky regions of the sea floor with high backscatter in water depths of ~1500 m over the Barbados Accretionary Complex. The relationship of seafloor morphologic features such as faults, craters, and mud volcanoes with vent-gas plumes in the water column is indicative of substantial emissions from this region. Disappearance of the acoustic plumes at ~600 m is coincident with the top of CH4 gas hydrate stability in the water column. In the plumes, natural gas hydrate shells that form at the gas-water interface and armor the gas from dissolution during ascent likely encapsulate bubbles. Ascent-driven pressure change in the bubbles causes shattering of shells forming gas hydrate shards that rise with the ascending plume and add to its acoustic reflection strength. The multiphase fluid consisting of gas, shelled bubbles, shards, and water changes character at the top of gas hydrate stability where the hydrate dissociates and dissolves. Differentiating sources and further characterizing emissions will provide baselines and also contribute to understanding the relative importance of the different emissions sources.
Improved Geological Model Calibration Through Sparsity-Promoting Ensemble Kalman Filter
Authors: Tarrahi Mohammadali , Afra Sardar
Published: April 2016

Calibrating complex subsurface geological models against dynamic well observations yields to a challenging inverse problem which is known as history matching in oil and gas literature. The highly nonlinear nature of interactions and relationships between reservoir model parameters and well responses demand automated, robust and geologically consistent inversion techniques. In the recent years, there has been significant progress in automated history matching methods mostly categorized as gradient-based and ensemble-based techniques. Ensemble-based methods such as ensemble Kalman filter (EnKF) have proved to be successful in adjusting reservoir parameters to match observed dynamic data. To calibrate the reservoir model and update the distributed parameters in geologically robust way it is crucial to utilize a parameterization method. Parameterization techniques also aim to make the inversion process more efficient by reducing the dimension of the model parameter.

Recently in the fields of image processing and data mining, sparse parameterization and image reconstruction are gained considerable attention. We propose a novel automated history matching method by employing EnKF along with a sparsity-promoting parameterization technique. To improve the performance of EnKF in capturing complex geological features such as channelized reservoirs, we employ sparse constraints to construct the reservoir model from the observed dynamic well data. For the parameterization purpose we investigate utilizing various basis functions or models such as singular value decomposition (SVD) and discrete cosine transform (DCT). The combination of EnKF analysis equation with sparse reconstruction algorithm such as Matching Pursuit (MP) will enhance the inversion results. We also investigated effects of different geologically trained dictionaries or basis such as K-SVD and also the impact of combining various basis sets.

We applied the proposed sparsity-promoting EnKF to several numerical examples to estimate reservoir distributed properties from well production data. The enhanced EnKF method with sparse constrained parameterization showed promising improvement comparing to standard EnKF and also EnKF with standard parameterization. The proposed inversion technique propagates and updates an ensemble of geological models through integration steps and provides more consistent distributed parameter fields with the prior geology of the subsurface formation.

The sparsity-promoting EnKF is a derivative free history matching method which is also able to perform uncertainty assessment because of its ensemble based nature. Parameterizations along with sparse selection of basis functions make the calibrated solutions of this method more geologically consistent. This method is especially suitable for resolving more complex geological structures such as channelized formations which are generated with multi-point geostatistics techniques.