bluuebunny/crossref_metadata_2025_split 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

Abstract
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.
Early Project LDHI Dosage Assumptions versus an Extensive Laboratory Study
Authors: Conrad P. , McCarthy R. , Golczynski T. , Spratt P. 
Published: April 2018

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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 &gt; 5,000 psi and high elongation at break &gt; 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.