bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Dual Refrigerant Expansion Cycle for Liquefaction
Authors: Kim Hyobin , Kim Mungyu , Kim Youngrae , Kim Minseok , Lee Kihwan , Kim Minki , Min Joonho , Lee Donghun , Jang Jungmoon , Kim Junghoon
Published: April 2018

This paper presents a LNG Liquefaction cycle configuration using two stages of methane expansion and a single stage of nitrogen expansion (Dual Refrigerant) to improve the efficiency of the conventional methane and nitrogen refrigerant expansion cycle. The chosen configuration further optimizes the composite cooling and heating curve of the liquefaction cycle, resulting in a higher thermodynamic efficiency. The production efficiency of the liquefaction cycle can be improved by reducing the interval between the cooling curve of the natural gas and the warming curve of the refrigerant: the closer both curves are, the better the efficiency of the cycle. This optimization is achieved by adjusting the refrigerant operating temperatures and pressures. The advanced dual refrigerant expansion cycle includes three levels of expansion, each having different temperature and pressure levels. In the methane expansion loop there are two stages, which are classified warm and cold. The warm loop is applied in the pre-cooling zone and the cold loop is responsible for the main liquefaction. The nitrogen loop is a single stage and is used for sub-cooling. This configuration allows the methane and nitrogen warming curve to closely match the cooling curve of the natural gas cooling curve by changing the methane and nitrogen warming curve from two straight lines into multiple intersecting straight lines of different gradient. That is to say, the additional new methane expander generates an added inflection point within the cold composite curve. As a result, thermodynamic inefficiencies are minimized and the power requirements are reduced when compared to Methane & Nitrogen Expansion Cycle. In comparison with other previous expansion cycles, the cycle efficiency has increased approximately from 13.13 to 12.08 kW/ton/day (8% efficiency increase) assuming similar feed gas (methane: 80%, MW: 21.38). The composition of this feed gas is representative for associated gas or pipe line gas which is preliminary treated to remove bulk water and hydrocarbon condensate. A case study is presented for an open sea associated gas FLNG concept, comparing three kinds of liquefaction processes (Double Nitrogen Expansion Cycle, Methane & Nitrogen Expansion Cycle and Developed Dual Refrigerant Expansion Cycle). A Life Cycle Cost (LCC) analysis based on Net Positive Value (NPV) also shows an improvement in terms of project NPV, against a minor increment of the CAPEX of these cycles.
42" Subsea Connector & Open-PLET Technology
Authors: Ali Mohammed Hasan
Published: April 2018

With the increasing demand in the gas field developments around the world which typically characterizes a large diameter subsea to shore gas export pipelines, tie-in connectors become necessary to be able provide to connection between various subsea structures. To qualify a new large bore connector present significant cost and schedule challenge especially for pipe sizes above 34′ and associated risks during installation. BHGE with its 25 plus years of experience and track record in this product category has successfully developed and installed 42′ subsea clamp connector combined with proprietary open-PLET technology which has increased the reliability and safety during installation. The 42′ M5 connector was used to tie-in the Ichthys gas export trunkline to the subsea structures which to date is world's largest subsea connector for flowlines tie-ins.
Early Project LDHI Dosage Assumptions versus an Extensive Laboratory Study
Authors: Conrad P. , McCarthy R. , Golczynski T. , Spratt P.
Published: April 2018

Early phases of development for projects with hydrate mitigation strategies incorporating low dose hydrate inhibitors (LDHIs) are often subjected to assumptions in LDHI dosing requirements, which impact both CAPEX (tanks, pumps, umbilicals) and OPEX (chemical spend). These assumptions can influence the viability of projects moving forward, especially in low-cost environments, and has reemphasized the need for a critical evaluation of the state of the industry for LDHI performance under a variety of conditions. Within this paper, a series of tests examining the impact of produced water salinity and water cut on LDHI effectiveness using a range of hydrocarbon fluids was carried out using high pressure rocking cells. Standard test conditions were utilized throughout the investigation in constant mass rocking cells with an initial pressure of 2,500 psi using synthetic Green Canyon gas. Salinity sensitivity studies maintained held water cuts constant at 40 vol% while varying the salinity from condensed water up to 250,000 TDS NaCl. Water cut sensitivity studies examined both, 35,000 TDS (seawater) and 125,000 TDS, brine conditions while the water cut was varied from 5% to 80%. Salinity sensitivities were repeated using two commercially available anti-agglomerates (AAs) as standards and three hydrocarbon phases, including two different black oils and kerosene. Water cut sensitivities were conducted with one commercially available AA and two hydrocarbon phases: a black oil and kerosene. The significance of these matrices demonstrates that project planning should include baseline testing with fluids representing actual expected field conditions to better assess AA requirements for new developments. In many cases, project assumptions about costs or chemical performance should be reexamined.
Mitigating Flexible Riser Risk by Focused Monitoring and Digital Analytics
Authors: Green L. M. , Nordsve N. T. , Gjendal A , Lillevold P , Muren J , Hanssen E. B.
Published: April 2018

This paper presents the development of a predictive model for topside annulus vent gas flow from a flexible riser and the infrastructure to feed live operational data from the offshore process, subsea and vent systems to a cloud solution. The presented data is accessed and processed through analytics prior to live presentation on a digital platform accessible to offshore and onshore subsea engineers, and to anyone inside or outside the operator's organization in need for the data and operational status.

The aim is to use all available sensor data related to five operative high temperature flexible risers to reveal emerging evolvement of a failure mode previously experienced on similar risers in similar service. Carcass collapse in the seabed segment of the flexible riser is identified as the key failure mode in need for mitigation actions. The collapse is caused by excessive pressure in pipe designs with multi-layer pressure sheath, and has been observed on several occasions during startup after longer maintenance and shut down periods. As the flow rate in the risers is moderate and the performance of wells varies, it is not possible to identify the carcass collapse by pressure drop monitoring, not even with detailed analysis of pressure differences topside and subsea.

Concatenating all pressure, temperature, annulus volume testing, inspection and annulus monitoring data in real time established the basis for applying machine learning techniques to identify when a carcass failure emerged. Combining data analytics with in depth understanding of the flexible pipe cross section, failure mode development and pipe dissection experiences enabled an analytics solution providing early warning of an emerging damage.

As all the utilized measurement data was available, also for two previous carcass damages in identical risers, validation and confidence of the models could be established to identify these damages early. On this basis, it was concluded that the focused monitoring and digital analytics gave sufficient risk mitigation for the five remaining operating risers of the same type.
Long Gas Tiebacks – Pseudo Dry Gas Systems
Authors: Thomas Lee , Liebana Laura , Wood Terry , Stokes Stephen , Luff Richard
Published: April 2018

Due to the laws of physics and multiphase flow, subsea tie back systems are generally limited to approximately 110km as a single pipeline or 150km as dual pipelines after which the production plateaus are shortened and increasing amounts of reserves remain in the ground. This paper presents an overview of an innovative new technology which demonstrates that gas tie-backs can be achieved without the need of compression.

The premise of the technology is to achieve pseudo-dry gas conditions through intermittent in-line separation with segregated transport of the associated liquid phase. Achieving near dry gas conditions in the main production conduit removes hydraulic constraints on line size and turndown, leading to improved recovery for long distance tieback opportunities.

The paper demonstrates this innovative technology and its value proposition by means of a ‘bench-marked’ study of a 200km long gas tie-back in 1,800m (5,900ft) of water. The Computational Fluid Dynamics (CFD) work has demonstrated high separation efficiencies at significant superficial gas velocities, while the required hardware fits within the installation envelope of an ‘In-line’ pipeline tee. This has been coupled to the flow assurance work showing improvements in recoverable reserves, while leading to capital expenditure reductions of upwards of 50% due to the removal of offshore structures.
Unmanned Aerial Vehicles for Survey of Marine and Offshore Structures: A Classification Organization's Viewpoint and Experience
Authors: Wen Feng , Wolling James , McSweeney Kevin , Gu Hai
Published: April 2018

This paper discusses the benefits of using Unmanned Aerial Vehicles (UAVs) as inspection tools to support surveys of marine and offshore assets, from a class organization's viewpoint and understanding, based on industry case studies and experiences for both internal and external structure surveys. Capabilities and limitations of using UAVs are compared to current survey methods. Finally, possible future uses of this technology will be discussed.

Some specific inspections for marine and offshore assets, such as those conducted at height or in confined spaces, are typically performed by surveyors. These inspections can be expensive, time consuming, and disruptive. This paper presents key challenges driving the need for UAV inspection, and benefits offered by this new technology. General acceptance criteria and requirements of UAV inspection (e.g., data acquisition), based on previous industry experience, are introduced. Available UAV systems are presented, with a brief introduction of typical UAV types. General performance and lessons learned, based on previous UAV field tests, are summarized. Two case studies further highlight field test results. Also, the paper discusses existing and potential data post-processing methods (e.g. regression analysis), and how these methods leverage UAV technology in structure monitoring and inspection.

The use of UAVs can help reduce the risk associated with the above mentioned inspections by reducing hazard exposures for workers. Use of UAVs can also have a positive impact on operational activities through increased inspection frequency, improved inspection efficiency and better data collecting capability. With proper utilization, the data collected by UAVs can augment and complement such technologies as photometric processing, structural condition monitoring and failure recognition. All of these can help refine shipyard specifications, enhance repair plans and reduce overall cost by providing greater knowledge of the asset's condition.

Currently, the mainstay of UAV inspection is the High-Definition (HD) camera, for photograph and video data collection. However, the impact of emerging technologies on UAVs such as infrared emission sensors, thickness gauging tools, LiDAR scanners, etc., to the Class survey scope requires further study and research.
Leakage Monitoring of Subsea Blowout Preventer Control System
Authors: Wassar Taoufik , Mutlu Mete , Franchek Matthew A. , Guiterrez Jose
Published: April 2018

Presented in this paper is a model-based approach for leakage detection and identification in subsea blowout preventer (BOP) hydraulic control system. A physics-based model is implemented to quantify the overall leak rate of BOP control fluid from surface hydraulic power unit (HPU) to subsea BOP operator. The model input is the measured pressure at the surface main accumulator stack, and the model parameters are accumulator stack characteristics including precharge pressure and total fluid volume. To isolate the leak path in the BOP control system, a model-based leak indicator is derived for each of the control pod main rail pressure regulators. The performance and robustness of the proposed approach is investigated by conducting a what-if analysis using a virtual BOP model built in a simulation environment. The fluid leak monitoring algorithm is applied to field data collected from several deepwater drilling rigs. The results show that the proposed methodology is able to detect and monitor control fluid leak within the BOP control system.
System Model Integration in Subsea Design
Authors: Hudson Abe , Kratzke Ron , Baker Jason
Published: April 2018

The objective of this paper is to show how a system composed of many individually designed and manufactured components each with independent descriptive and analytical models of varying definition can be developed and managed by an integrated systems model.

Typical engineering design methods require the engineering team to manually coordinate and integrate the engineering domains: electrical, hydraulic, mechanical, software, etc. This effort can take an inordinate amount of time and resources and is rife with errors, which inevitably lead to specification issues. Model-based system engineering (MBSE) is a method used extensively in the military and aerospace industries to reduce component integration and system development time for complex systems. This paper examines methods used to integrate the component models during development of a design for a subsea system. The authors describe the application of a commercially available MBSE toolset extended to integrate with analytical physics based design software.

The challenges, advantages, disadvantages, and suggested improvements for integrating the models are explored. The authors discuss how their process supports the domains of system engineering including: requirements, behavior, physical architectures and verification strategies, and how this intimately aligns with the typical engineering domains. Finally, the authors discuss the development of an application programming interface (API) to integrate the models and manage the transfer of data between disparate software tool sets and provide suggestions for future projects of similar complexity. The paper discusses how the methods applied reduce duplicate work and specification errors, achieving a reduction in rework, and ultimately, development time and cost.

The MBSE methodology has not typically been applied broadly in energy. This paper highlights a successful deployment of MBSE covering early stages of conceptual design to manufacturing. The API developed to permit seamless integration of multiple systems engineering development tools is unique for this type of application. The interoperability between development tools is highly sought after in the engineering community and enables many advanced capabilities for development teams. Some of these capabilities include: end-to-end traceability, automated model development, automated design verification, and automated document generation and design specification.
Correlation of Numerical Simulation and DIC Strain Measurements for a Multilateral Junction while Subjected to High Internal Pressure
Authors: Liang Aihua , Steele David , Droessler Mark
Published: April 2018

This paper investigates stress and strain distributions determined through finite-element analysis (FEA) simulation and three-dimensional (3-D), digital image correlation (DIC) measurements obtained during full-scale testing of a Technology Advancement of Multilaterals (TAML) Level 5 multilateral junction prototype subjected to high internal pressure.

A multilateral well consists of one main wellbore with one or more lateral wellbores drilled from the main wellbore. The point at which a lateral is drilled from the main wellbore is identified as the wellbore junction. The wellbore junction's integrity is important to the success of the multilateral well construction (Samuel and Gao 2007). A TAML Level 5 junction is necessary to create pressure isolation across both lateral and mainbore legs to withstand high-pressure/high-temperature (HPHT) conditions in deeper oil and gas wells (TAML 2002).

This study discusses a completion system TAML Level 5 multilateral junction subjected to a qualification program, including internal and external pressure cycles with the junction in a deployed position to verify pressure integrity. The junction was evaluated through both numerical simulation and full-scale physical testing of a prototype, which was designed to be run in 10-3/4-in., 65.7-lb casing with a 5-1/2-in. lateral leg and a 3-1/2-in. mainbore leg.

This paper investigates stress and strain distributions determined through FEA simulation and 3-D DIC measurements obtained during full-scale testing of a junction at 6,000-psi internal pressure. Although DIC has been widely used for strain measurements within the industry, it was introduced into the junction-test program to meet increasingly challenging environments. Compared to conventional strain-gauge measurements, DIC allows for full-field strain measurements, including points at which complex geometries exist, such as the external intersection of the main and lateral legs, which is commonly the critical area with high stress concentrations. A correlation and comparison between the numerical simulation and DIC measurements are discussed to qualitatively validate the FEA model with experimental results.

The petroleum industry requires more advanced technologies as wells are drilled in more challenging environments (i.e., deep sea, artic environments, higher pressures, etc.). To provide these advanced technologies, engineers need the capability to help ensure their designs meet the requirements of such challenging environments. DIC provides a means to qualitatively validate the numerical simulations for complex designs.
Recent Advances in Enhanced Oil Recovery Technologies for Unconventional Oil Reservoirs
Authors: Balasubramanian S. , Chen P. , Bose S. , Alzahabi A. , Thakur G. C.
Published: April 2018

Unconventional resources have significantly transformed the landscape of the oil and gas industry. The primary recovery factor ranges anywhere from 2% to 8% for the various shale plays throughout the United States. Hence, it is imperative to exploit the vast potential of unconventional reservoirs and increase the recovery factors beyond primary depletion by implementing improved and enhanced oil recovery (IOR/EOR) methods. This paper presents detailed review of the advances in IOR/EOR technologies applied to unconventional oil reservoirs.

A thorough review of the pertinent published literature on IOR/EOR was performed. Results of EOR application to unconventionals shared by various operators in their investor presentations and press reports were also analyzed. The IOR/EOR studies were classified into laboratory experiments, numerical modeling and field laboratory trials (pilots). In addition, the field trials were also analyzed based on the representative shale plays.

Most of the studies performed for the application of EOR technologies to unconventional oil reservoirs have been limited to experimental investigations and numerical simulation studies. The research revealed that miscible gas injection (produced gases, CO2, etc.) is the most promising method among the EOR techniques (miscible gas, water flooding, surfactant, chemical and polymer). Experimental studies showed that CO2 injection had the highest potential of improved recovery in unconventionals followed by produced gas injection and that diffusion was the most predominant mechanism. Surfactant injection showed the next best potential to increase oil recovery by altering the wettability of rock in laboratory experiments. The gas injection pilots showed that sufficient injectivity was achieved mainly due to the injection induced fractures and did not exhibit any significant effect of diffusion. Conformance control remains a big challenge especially due to the channeling of the gas through the fractures. Produced gas injection pilots in the Eagle Ford formation have demonstrated the greatest success in increasing oil recovery. However, there are many inconsistencies between the laboratory investigations and field trials that needs reconciliation. Further research is necessary to bridge the gap and improve the scaling from laboratory to field.

This methodical study elicits the learnings and challenges from the application of different IOR/EOR technologies to unconventionals at various scales (micro to macro to field scale). In addition, ideas for future research are recommended to improve the understanding of the complex mechanisms of EOR in unconventional oil reservoirs. These include optimizing gas injection schemes (huff-n-puff, continuous injection) based on key parameters such as permeability and investigating fracture placement for improving the drainage area and inter-well communication.
Degradable Packing Element for Low-Temperature Fracturing Applications
Authors: Duan Ping , Sadana Anil , Xu Yingqing , Deng Guijun , Pratt Barbara
Published: April 2018

Plug-and-Perf with composite plugs is a commonly used method for multistage hydraulic fracturing treatment in North America shale plays. Composite plugs must be drilled out after the fracturing operation to allow flow of hydrocarbons or produced fluids to the surface. This paper presents a completely degradable packing element for low temperatures, at 125°F or above, and high-pressure (10,000 psi) applications that require no subsequent drilling-out operation.

The degradable packing element is made of a polyurethane material and special fillers using an innovative manufacturing method to achieve the desired degradability at temperatures of 125°F or above. Three-dimensional solid modeling and nonlinear finite element analysis (FEA) were performed to finalize the packing element design. Full functional tests on sealability and degradability to meet specific operational requirements were performed.

This new degradable polyurethane sealing material is extremely strong, with a tensile strength > 5,000 psi and high elongation at break > 400%. Degradability and sealability are two key functions of the disintegrating frac plug packing element material. The packing elements degrade completely in light brines in a temperature range from 125 to 200°F. Full plug tests with this degradable material as a sealing element demonstrated the sealing ability to hold 10,000 psi for five hours. All components of the plug including sealing element fully disintegrate after fracturing operation in light brines.

A new polyurethane-based degradable packing element material for low wellbore temperatures (from 125 to 200°F) was developed. Introduction of this new sealing material will accelerate the development of interventionless tools for unconventional shale completions at a wide range of application temperatures.
Pressure Relief Valves Fugitive Emissions Testing
Authors: Tezzo D. Emile , Gado Amr , Deng Calvin
Published: April 2018

Fugitive emissions, which are unintended emissions of gases or vapors from pressurized plant components, have been a key concern for operators of oil and gas, chemical and petrochemical plants as well as regulators for a long time. Fugitive emissions could be hazardous, contribute to atmospheric pollution, and could represent an economic loss for the plant. As the number of potential leak sources at large industrial facilities can be numerous and difficult to identify, controlling fugitive emissions is particularly challenging.

One particularly challenging possible source of fugitive emissions is valves in general, (see Figure 1). Particularly, pressure relief valves are not exempt from fugitive emissions. Bolted and threaded components and features that constitute pressure relief valve designs suffer the same fate. Unlike manual valves, pressure relief valves are not designed with packing (or stuffing boxes) to minimize or control emissions. Another source of challenge is that, traditionally, an industry-wide acceptable standard for testing PRVs for fugitive emissions has not been established and adopted.

Emerson Automation Solutions teamed up with a leading oil and gas producer and a third-party testing laboratory to embark on an industry-leading, first-of-its-kind fugitive emissions testing program for pressure relief valves. The valves that were subjected to this test program are the Anderson Greenwood pilot-operated pressure relief valves (Figure 2, left) and Crosby direct spring-operated pressure relief valves (Figure 2, right) and OMNI portable thermal relief valves.
High Strength Steel for HP/HT Riser Applications and Cost Benefits
Authors: Karunakaran Daniel , Jones Richard , Thurel Elina , Linne Cedric
Published: April 2018

HP/HT applications in conventional steel grades require large wall thickness for the pipeline and risers. Design of risers with large wall thickness, especially in deep waters and ultra-deep waters, pose great challenges due to: large payloads on the floater, welding of large wall thickness, fatigue at hang-off and touch down point for Steel Catenary Risers (SCR) and Steel Lazy Wave Risers (SLWR).

Application of high strength steel for HP/HT application as riser material is an attractive alternative. High strength steel reduces the wall thickness and thereby reduces payloads on floaters. Further, risers with reduced wall thickness have other added cost saving due to reduced buoyancy requirement for SLWR or hybrid riser solutions which can be significant depending on the application. Furthermore, reduced wall thickness improves weldability.

The paper addresses the engineering assessment and cost benefits of using high strength steel. Furthermore the paper will present the recent qualification programmes, carried out in collaboration with Vallourec, aimed at validating seamless Grade X80 linepipe material and welding solutions for reel-lay installation.

The results clearly highlight the technical and cost benefits of applying high strength steel for HP/HT riser application. Preliminary fatigue test results demonstrate that high fatigue performance can be sustained with established girth welding procedures with appropriate control of pipe fit up tolerances and weld soundness.
Horizontal Well Placement in a Thin Heterogeneous Carbonate Reservoir, Utilizing Azimuthal Sonic and Resistivity Measurements, a Case Study from Offshore Abu Dhabi
Authors: Serry Amr M. , Al-Hassani Sultan , Al-Tamimi Ibrahim , Khan Owais A. , Naseem Shafiq , Mostafa Hassan , El Kholy Mohamed , Bassiony Aly
Published: April 2018

Proper Well Placement in a thin carbonate reservoir could be challenging due to high geological uncertainty. Using radioactive sources to evaluate porosity & formation dipping is effective, but localized geological and structural uncertainty resulted in a decision to not use radioactive sources in the well.

This paper is a case study illustrating utilizing absolutely sourceless BHA including combination of azimuthal sonic with azimuthal resistivity distance to boundary technology as a highly effective alternative sourceless geosteering method & adds extra formation evaluation values.

Azimuthal resistivity was used for larger scale geosteering, landing the well within the reservoir, and positioning it close to the target zone, while azimuthal sonic was used for smaller scale precision placement within the target zone itself, with steering decisions being based on porosity.

A standard LWD sonic tool would have provided an average response to the formation within the zone of measurement, with the transit time for both compressional and shear effectively corresponding to the fastest route from transmitter to receiver.

The azimuthal sonic tool however, measures the transit time for both compressional and shear slowness in 16 sectors around the borehole. As the drill string rotates, waveform data is acquired in 16 fixed-orientation azimuthal bins. The waveforms are processed to yield azimuthally oriented compressional and reflected shear slowness values, with associated porosity values derived from the compressional data. It is these porosity values that were compared and contrasted to ensure positioning of the wellbore within the narrow high porosity zone.

Borehole images constructed from both compressional and shear slowness data provided clear indication of intersecting beds. Compressional data compared well with conventional images from LWD azimuthal gamma and density tools, and was used to identify formation dip and stratigraphic position of the wellbore.
Opportunities and Challenges of Remote Operating a ROV Embarked on a USV
Authors: Lachaud Emilie , Monbeig Yodrick , Nolleau Pierre , Hardy Antoine , Thompson Matthew , Lardeux Mathieu
Published: April 2018

An Unmanned Surface Vessel (USV) deploying a Remotely Operated Vehicle (ROV) has the potential to replace a conventional manned vessel for various operations from field installation to operational support (including inspection, maintenance, repair and drilling support) and decommissioning. The USV deploying ROV (also written as USV+ROV) is already emerging in the oil and gas industry with maturing technology developments and increasing capacities and performance of autonomous vehicles and remotely operated systems. Beyond the safety improvement generated by the absence of personnel onboard the USV, this solution intends to significantly reduce the subsea intervention costs while improving the intervention (planning) flexibility. One of the advantages of the technology is that the operator is located offshore on another vessel or onshore while maintaining a real-time control with the USV+ROV. Threfore, communication link between the operator and the USV+ROV system is critical.

To mitigate limitations (latency and bandwidth) of the communication link, an obvious solution is to evolve disruptively towards autonomous system. However, incremental autonomy approach with immediate return on investment could be made possible with careful mission's analysis and thorough analysis of communications limitations on operation efficiency.

This paper will present only a methodology that attempts to develop a deep understanding of the communication physical effects and their consequences on performance of targeted remote operations. The impact of latency and bandwidth are studied using interactive simulations associated to future offshore trials. At the time of writing, the simulator has been commissioned and a proof of concept trials has been prepared.
Developing Weld Defect Acceptance Criteria for a Swaged Pipe-in-Pipe System
Authors: Zhou D. , Sriskandarajah T. , Bamane M. , Tews P. , Dugat S.
Published: April 2018

Swaged pipe in pipe construction has been increasingly used for offshore pipeline system. Double joint pieces of swaged pipe-in-pipe are typically welded together on a J-lay/S-lay vessel. The swaged end joint is fabricated through a cold deformation process to the outer pipe that is then welded to the inner pipe. The pipe-in-pipe system has excellent thermal insulation characteristics. However, the integrity assessment of pipe-in-pipe swage weld is outside the range of validity of existing engineering critical assessment (ECA) codes, and this presents challenges in developing welding defect acceptance criteria, associated welding qualification and automatic ultrasonic testing (AUT).

This paper highlights the assessment and inspection challenges faced and efficient solutions developed for the swage weld system. Comprehensive 3D finite element (FE) analyses were developed to consider mixed mode fracture for defects at the swage weld. Representative fracture testing was carried out as part of welding qualifications.

The methodology was deployed to derive and optimise weld defect acceptance criteria specific to flowline and pipeline end termination (PLET) special joints, considering laydown, initiation and normal lay installation scenarios. The welding defect acceptance criteria were applied to the swage weld through a newly developed AUT system which can fit in small diameter pipelines.

The developed assessment solutions will greatly benefit the future pipe-in-pipe swage weld system assessment and potentially bring significant cost savings to the industry.
On Extreme Surface and Sub-Surface Currents Driven by North Brazil Current Rings Offshore Suriname
Authors: Schiller Rafael V. , Smith Rosemary B.
Published: April 2018

North Brazil Current Rings (NBCRs) are mesoscale oceanic vortexes (100-500km in diameter) that significantly affect current conditions offshore Suriname and other countries in the Western Equatorial Atlantic. NBCRs propagate in deep water from the Brazilian Amazon region towards the Lower Antilles at a rate of about 8-9 rings per year. With maximum surface velocities easily reaching more than 1m/s, NBCRs can represent a major metocean hazard to the offshore O&G Industry. Hence, the metocean characterization of NBCRs is key for safe asset design and operations. This paper presents novel findings of NBCRs extreme surface and sub-surface currents based on recent long-term mooring-based current measurements. The measurements consisted of 14 months of full-water column current records at three locations in deepwater offshore Suriname. Throughout the measurement period, the three locations were impacted by 8 NBCRs; 5 were surface-intensified (maximum currents near the surface and ring restricted to the upper 250m), 2 were deep-reaching (maximum currents near the surface but strong currents reaching down to ~800m) and 1 was subsurface-intensified (maximum currents at ~250m below the surface, weak surface current signature). All surface rings presented maximum currents well above 1m/s while one ring peaked at 1.65 m/s. The subsurface ring was unique in nature as near-surface currents peaked at ~0.6m/s while the sub-surface currents peaked at ~1.2m/s. The impact of some rings lasted for as long as 1 month. Our findings expanded on the complexity of deep water currents in offshore Suriname and how they represent unique operational and design challenges.
Gullfaks Subsea Compression: Early Operational Experience from the World's First Subsea Wet Gas Compression System
Authors: Bøe Caroline , Hjelmeland Mads , Torkildsen Bernt Helge
Published: April 2018

Subsea boosting has today achieved a significant track record and it has been recognized by major oil companies as an important part of enhanced drainage strategies. For gas fields compression is the only viable means of artificial lift and subsea compressions offers many advantages over conventional topside compression such as increased ultimate recovery. The advantages of subsea compression increase with increasing tie-back distance.

Particular features and benefits of subsea multiphase or wet gas compression are discussed in general and the particular experience with a subsea wet gas compression system now in operation at the Gullfaks field on the Norwegian continental shelf is presented.

Commissioning of the Gullfaks Subsea Wet Gas Compression System started in 2015. The system ran for one month but had to be taken out of operation for almost two years due to umbilical leakage. The system was restarted in 2017 and has been running successfully ever since, boosting wet gas and increasing the production from several wells. The system flexibility is exploited in a more extended way then ever expected during the project phase, and allows the operator to take advantage of many opportunities including increased oil recovery, and kicking off dead wells and enabling stable well back-pressure. The fundamental benefits of subsea compression are now demonstrated.
An Evaluation of an Air Gap Assessment Using a Focus Wave Technique
Authors: Kim Youngkook , Zhang Yali , Pang Andrew , Chua Kie Hian , Xu Hai Hua , Liu Jing , Ma Pei Feng , Choudhary Ankit , Hussain Anis , Merchant Aziz Amirali
Published: April 2018

It is challenging to predict the air gaps of floating offshore structures due to the property of ocean waves and induced motions of the structures. Linear analysis based on potential flow theory is common to be used for air gap evaluations before carrying out air gap model tests with typical 3-hour irregular wave. CFD (Computational Fluid Dynamics) simulations are getting popular for the offshore industry to reduce uncertainty of the design. However, simulation of short-term irregular sea for the air gap evaluation using CFD is time consuming. Because non-extreme events are not of interest to the designers for air gap assessment, combination of focus wave, based on NewWave theory, and probability distribution of wave crest is used to generate the most probable extreme wave and applied for the air gap evaluation in this study. The developed extreme wave is first evaluated against the undisturbed waves in the model tests. Several wave crest distributions are compared to find the most suitable one for target wave when used with NewWave theory. Due to the non-linearity of NewWave and numerical dissipation, best practice methodologies are investigated to obtain the required target wave. By applying such a design wave in CFD, the air gap of a semisubmersible was assessed. The responses of the floater, i.e. motions and relative wave elevations, are compared against the several extreme events observed in irregular model test to evaluate the developed methodology. This study demonstrates how the focus wave technique can be used in CFD for air gap assessment instead of a 3 hour short term simulation.
A New Logging-While-Drilling Azimuthal Density Sensor for Large Borehole Applications—Gulf of Mexico Case Studies
Authors: Michel Franck , Parker Tim , Rennie Allan , Laroussi Nasreddine , Ehiwario Michael
Published: April 2018

In the current market, operational geology and geoscience asset teams have clear and aggressive financial reduction targets that need to be met without compromising the formation evaluation (FE) requirements of a well construction project. Advances in drilling and completion technologies and practices for deep-water wells commonly require operators to drill larger borehole sizes throughout the well construction process. For deep-water subsalt wellbores, this often implies exiting a thick salt layer with borehole deviation in borehole sizes ranging from 14.5 to 17.5 in.

This paper introduces a unique 9.5-in. nominal collar size logging-while-drilling (LWD) density tool that makes it possible to address the FE challenges encountered in large borehole sizes. Any LWD method that can provide crucial cost-effective and accurate FE data can add value to well drilling and logging programs.

The new tool provides density and photoelectric measurements in large-diameter boreholes. It also contains an ultrasonic sensor that can provide accurate borehole geometry information, which is useful for identifying stress-related breakout and providing accurate estimates of borehole volume for later placement of cement for zonal isolation.

In such settings, formation density measurements are crucial for determining key evaluation parameters, such as porosity and rock mechanical properties, but acquisition of these measurements can be challenging using existing LWD technologies. In addition, real-time structural dip information for subsalt environments provides insight for the interpretation of the geological structure of the field but is often difficult to obtain in large-diameter boreholes.

Several case studies demonstrate the value added by the new tool and its breadth of application, as well as the implications for pre-job analysis, bottom-hole assembly (BHA) modeling, data-acquisition procedures, sensor response analysis, and economic benefits to the operator.

The capability of acquiring logging data for interpretation purposes and to fulfill specific regulatory requirements without negatively affecting the drilling program provides a desirable cost-management opportunity.

The results presented here provide a reference for appropriate business cases to help justify the use of this unique LWD technology in drilling and logging projects involving large-diameter boreholes.
Recommended Design and Field Practices to Maximize the Value of Degradable Completion Systems
Authors: Aviles I. , Dardis M.
Published: April 2018

The introduction of new technology is critical for operators to expand their completion options, increase efficiency, and drive profitably in challenging environments. For unconventional reservoirs, hydraulic fracturing in cased or open hole has been key for the economic success of new ventures. The continuous evolution in Completion technology has led to many advances in efficiency by the inclusion of degradable technologies. These technologies, when properly implemented, can reduce or even eliminate mechanical interventions, both during operations and post-stimulation. However, simply replacing current isolating technologies, balls or plugs, with one that will dissolve is not enough to capture the full value of these systems.

Many operators have decided to experiment with degradable technologies without adjusting their current completion strategies. This approach can result in mixed success. For those operators who did not achieve the potential of the technology, a closer look is needed to decide if the degradable technology is compatible with the operator's drivers and overall strategy. A thorough review of current operating practices and environments is essential to understand how degradable technologies may be utilized to reduce cost, risk, and time associated with completion activities.

In addition, the dissolution mechanisms must be understood to best decide how and when to use degradable devices. Environmental, procedural, and design considerations need to be evaluated to have a successful implementation of degradable technologies. These include: A) Environmental (e.g. reservoir pressure, BHST, etc.), B) Procedural (e.g. pump down fluid, stimulation fluid, etc.) and C) Design (e.g. tool design, degradation mechanism,etc.)

This paper will provide a set of comprehensive recommendations to assist in job planning and execution. Examples will be drawn from various operating environments with their unique challenges discussed and analyzed. Following these recommendations, degradable technologies can more successfully be implemented and the reduction of costs, risks, and time associated with mechanical interventions can be achieved.
Effective Use of Laboratory Measurements on Eor Planning
Authors: Moreno J. E. , Flew S. , Gurpinar O. , Liu Y. , Gossuin J.
Published: April 2018

EOR design and risk mitigation often involves the use of laboratory results to further characterize frontal movement and interaction of the EOR agents within the reservoir; laboratory tests and protocols have been designed to address such uncertainties and constitute now a fundamental part of any EOR deployment. While the need for laboratory tests is recognized, specifics of the tests and uncertainty of the laboratory tests themselves are not widely known, or fully understood, which has the potential of inadequate usage of the laboratory results on the EOR performance estimations.

This paper aims to provide guidance on use of the laboratory results in numerical models by identifying and pairing specific laboratory measurements to numerical requirements; that is recognizing what parameters are directly measured and which are estimated indirectly from either laboratory and field measurements.

This paper addresses the requirements for chemical, miscible and WAG processes; and highlights the caveats of translation of the measurements onto numerical models as well as the inherent measurement uncertainties. A comprehensive numerical investigation is used to illustrate the effect and scalability of laboratory measurements for different displacement scenarios, accounting for finite-difference grid size, viscous-gravity forces, concentrations and fluid interaction. These results are used to further refine the remaining uncertainties on the displacement characterization and provide a solid start for the design of any field measurements including EOR pilot operations.
Mechanical Behavior of Degradable Thermoplastic Composites
Authors: Celestine A. , Zhu S.
Published: April 2018

Long fiber nylon 6 composites were subjected to hot, wet environments, similar to those existing downhole, for up to two days. The effects of fiber type on moisture absorption and subsequent degradation of mechanical properties were investigated. Specimens with magnesium oxide (MgO) embedded in the matrix were also prepared to study the effect of the MgO additive on moisture absorption and composite degradation. A direct correlation exists between the amount of moisture absorbed by the composites and the reduction in their mechanical properties. The type of fiber, whether glass or carbon, played a significant role in the degradation of mechanical properties with the glass fiber composites experiencing a larger reduction in strength, modulus, and fracture toughness than the carbon fiber composites. The presence of MgO served to enhance moisture absorption in both the glass fiber and carbon fiber composites and increased the degree of mechanical property degradation.
Geoscience Overview of the Hebron Field
Authors: Cornaglia Vincent , McNeill Andrew
Published: April 2018

This paper is a subsurface introduction to the Hebron Field focusing on field discovery, delineation and development project history as well as geoscience and reservoir background. We will show how field understanding has evolved over time and how technology and data quality improvements impacted this project. For example, we will show how the recent IsoMetrix seismic survey has contributed to reservoir definition and architecture understanding. Finally, we will review the first drilling results after about six months into the drilling campaign.
On the Limiting Weak-type Behaviors for Maximal Operators Associated with Power Weighted Measure
Authors: Hou Xianming , Wu Huoxiong
Published: April 2018

Let
$\unicode[STIX]{x1D6FD}\geqslant 0$
, let
$e_{1}=(1,0,\ldots ,0)$
be a unit vector on
$\mathbb{R}^{n}$
, and let
$d\unicode[STIX]{x1D707}(x)=|x|^{\unicode[STIX]{x1D6FD}}dx$
be a power weighted measure on
$\mathbb{R}^{n}$
. For
$0\leqslant \unicode[STIX]{x1D6FC}<n$
, let
$M_{\unicode[STIX]{x1D707}}^{\unicode[STIX]{x1D6FC}}$
be the centered Hardy-Littlewood maximal function and fractional maximal functions associated with measure
$\unicode[STIX]{x1D707}$
. This paper shows that for
$q=n/(n-\unicode[STIX]{x1D6FC})$
,
$f\in L^{1}(\mathbb{R}^{n},d\unicode[STIX]{x1D707})$
,
$$\begin{eqnarray}\displaystyle \lim _{\unicode[STIX]{x1D706}\rightarrow 0+}\unicode[STIX]{x1D706}^{q}\unicode[STIX]{x1D707}(\{x\in \mathbb{R}^{n}:M_{\unicode[STIX]{x1D707}}^{\unicode[STIX]{x1D6FC}}f(x)>\unicode[STIX]{x1D706}\})=\frac{\unicode[STIX]{x1D714}_{n-1}}{(n+\unicode[STIX]{x1D6FD})\unicode[STIX]{x1D707}(B(e_{1},1))}\Vert f\Vert _{L^{1}(\mathbb{R}^{n},d\unicode[STIX]{x1D707})}^{q}, & & \displaystyle \nonumber\\ \displaystyle \lim _{\unicode[STIX]{x1D706}\rightarrow 0+}\unicode[STIX]{x1D706}^{q}\unicode[STIX]{x1D707}\left(\left\{x\in \mathbb{R}^{n}:\left|M_{\unicode[STIX]{x1D707}}^{\unicode[STIX]{x1D6FC}}f(x)-\frac{\Vert f\Vert _{L^{1}(\mathbb{R}^{n},d\unicode[STIX]{x1D707})}}{\unicode[STIX]{x1D707}(B(x,|x|))^{1-\unicode[STIX]{x1D6FC}/n}}\right|>\unicode[STIX]{x1D706}\right\}\right)=0, & & \displaystyle \nonumber\end{eqnarray}$$
which is new and stronger than the previous result even if
$\unicode[STIX]{x1D6FD}=0$
. Meanwhile, the corresponding results for the un-centered maximal functions as well as the fractional integral operators with respect to measure
$\unicode[STIX]{x1D707}$
are also obtained.