bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shift Work Fatigue in the Petroleum Industry: A Proactive Fatigue Countermeasure
Authors: Meijer Koos , Robb Martin , Smit Jasper 
Published: October 2017

Abstract

Obj ectives/Scope
According to a recent survey of over 27,000 people in 22 countries, insomnia (or problems with sleeping) ranks as the second-most frequent health complaint after the common cold. Sleepiness / fatigue in the work place can lead to poor concentration, absenteeism, accidents, errors, injuries, and fatalities; fatigue has also been associated with some of the most notorious modern catastrophes such as the Exxon Valdez oil spill.
Shift workers are exposed to sleep disturbance as an inherent condition of work. When considering that the jobs of shift workers frequently involve safety- and production-critical tasks, managing the risks associated with shift worker fatigue should be an ongoing activity of O&G organizations. This has been identified and is addressed by industry guidance such as API RP 755, which is aimed at locations where shift workers commute to work. In contrast, the system described in this paper specifically addresses offshore locations where off-shift rest is taken offshore.

Methods, Procedures, Process
The innovation described in this paper, Night Fit, is based on solutions already applied at NASA and within the Dutch offshore industry. It is a light treatment method aimed specifically at the offshore shift work environments that optimizes work performance, health and safety by improving sleeping patterns. This has been shown to reduce workforce fatigue and thereby the risk of human errors. Special glasses and energy lights are used which, when applied to individuals on the basis of scientific understanding, has a positive effect on the secretion of sleep hormones and workforce energy levels. This will in turn support effective off-shift recovery and adaptation to shift changes -without the need for medication.

Results, Observations, Conclusions
At a previous project onboard Allseas’ pipe laying vessel ‘Solitaire’ the crew reported feeling less fatigued, more alert, and more energized during their work. The number of shift workers with a sleep quality grade of eight or higher (on a ten-point scale, with ten being highest quality), increased by almost 300% (21% before the intervention, and 62% six months after). In addition, the number of shift workers reporting feeling "very fatigued" during their shift decreased by more than 75%.
These and similar findings indicate that when properly understood, applying simple interventions -specifically, managing light exposure and providing training on the principles of sleep hygiene- contributes to fatigue risk reduction and enhances the performance, health, and safety of shift workers.
CFD Simulation of Critical Sand Deposition Velocity for Solid-Liquid Slurry Flow
Authors: Dabirian Ramin , Mohan Ram S. , Shoham Ovadia 
Published: October 2017

Abstract
Efficient transport of sand or cuttings is of great importance in oil and gas industry and the fluid velocity in these processes should be high enough to keep particles continuously moving along the pipe. This minimum fluid velocity below which particles deposit, defined as the critical velocity, depends on various factors including flow regime, particle size, particle concentration, phase velocities and fluid viscosity. The objective of this study is to investigate the effect of parameters such as particle size and liquid viscosity on solid particle transport in horizontal pipelines using Computational Fluid Dynamics (CFD) simulations and validate the numerical model predictions with experimental data.
CFD simulations have been conducted with a commercially available software, ANSYS-FLUENT. Eulerian model with k-ω SST turbulence closure model is used to simulate the fluid flow while particles are tracked as the Lagrangian phase. In these simulations eddy interaction model is included to consider the effect of flow turbulence on the particle track. The simulations are created for 0.05 m pipe diameter with 4 m length. The simulations are initialized at relatively high fluid velocity, which is gradually reduced until the particle velocity drops below the acceptable critical velocity.
The CFD simulation results are validated with experimental data from literature, Najmi (2015) and Najmi et al. (2016) for two particle sizes and multiple liquid viscosities. It was observed that the critical velocity values for liquid flows are comparable with CFD simulation results. The simulation results show that depending on the flow regimes (laminar or turbulent) and particle size, the critical velocity can demonstrate similar trend with carrier liquid viscosity as that of the experimental data. Also the CFD simulations and experiment results are compared with three models currently used in industry, namely Oroskar and Turian (1980) model, Salama (2000) model and Danielson (2007) model.
Improved Stoneley Wave Inversion Method for Fracture Evaluation
Authors: Collins M. , Hornby B. 
Published: October 2017

Abstract
The conductivity and density of fractures intersecting a borehole strongly influence well productivity, making fracture characterization an important aspect of reservoir management. A Stoneley-wave inversion process is presented to estimate borehole washout volume and fracture conductivity. In addition to identifying conductive fractures, the ability to detect borehole washout volume can impact other well operations, such as cementing or geomechanical property estimation, in situations where placing a caliper tool in the borehole is not desirable.
Low-frequency Stoneley wave reflections are commonly used to locate and evaluate fractures crossing a fluid-filled, open borehole. However, other mechanisms, such as the reflection from bed boundaries or changes in borehole size, can also induce secondary pressure waves. The inversion of reflectivity over a frequency bandwidth can be used to determine whether a secondary wave is likely the result of a conductive fracture, borehole washout, or the combination of both a washout and a fracture. The integration of additional information from other logs, such as borehole images, caliper, slowness, etc., is used to further distinguish fractures from bedding effects.
This paper describes the theoretical considerations and signal-processing techniques used in this integrated approach, and results from the analysis of field data are presented. The inversion bandwidth ranges from a minimum frequency of 300 to 500 Hz to a maximum of several kHz and is automatically adjusted based on data quality. Several wells were studied using forward modeling and numeric inversion. A comparison of inversion results to borehole images and caliper logs shows depth registration errors typically of 0.3 m (1 ft) or less. The inversion of all reflectivity measurements over the specified bandwidth distinguishes borehole washouts (stronger high-frequency response) from conductive fractures (stronger low-frequency response) and thus provides a more reasonable estimate of fracture conductivity compared to conventional wide-band integrated-amplitude reflection analyses.
Interaction of Non-Darcy Flow Regimes Coupled and Pore Volume Compaction in Shale Gas Formations
Authors: Davudov Davud , Moghanloo Rouzbeh Ghanbarnezhad 
Published: October 2017

Abstract
Shale resources have distinctive characteristics, such as micro-scale pore, ultra-low permeability, and complex fluid flow behavior. In order to predict productivity and deliverability in shale complex system, it is crucial to understand porosity and permeability relation. Since pore size distribution in shale formations is stretched down to nano-meters, the system response violates the predictions of Darcy's law. Depending on pore size and gas properties, non-Darcy flow mechanisms such as slip-flow, molecular diffusion, and Knudsen diffusion can affect the matrix deliverability. Although there are several models to predict permeability considering non-Darcy flow mechanisms, the impact of formation compaction has been neglected in calculations. However, correcting for pore volume shrinkage seems crucial for improved accuracy in evaluation of hydrocarbon reserve.
In this work, we analyze different flow regimes coupled with effects of pore volume compressibility for Barnett and Haynesville shale plays. The pore compressibility values are calculated based on Mercury Injection Capillary Pressure (MICP) data. Using our mathematical formulation, we divide the shale matrix into accessible pores and inaccessible part of the rock (IRP) and characterize pore compressibility values as a function of pressure.
As local pore pressure decreases, formation porosity, pore radius, Knudsen number and thus flow mechanisms are subjected to change with time. Hence, a new permeability model (total permeability) for shale matrix is developed which includes Darcy flow, slip flow, molecular diffusion, Knudsen diffusion, surface diffusion, and last but not the least pore compaction. The impact of pore shrinkage on total permeability reduction is analyzed.
Our results indicate that substitution of accessible pore compressibility with total bulk compressibility can significantly change the production behavior. The results suggest that predicted compressibility values for accessible pores appear to be two to up three orders of magnitude greater than bulk compressibility for Barnett and Haynesville samples. Moreover, effects of pore compaction on permeability during pressure depletion seem significant for the samples studied here. Since Non-Darcy flow mechanisms are sensitive to pore radius, permeability values derived based on laboratory conditions are required to be adjusted before upscaling to reservoir condition.
Mitigating Respirable Crystalline Silica with No Engineering Footprint
Authors: Jackson John , Hicks Jeff , Robinson Jamie 
Published: October 2017

Abstract
In June 2016,the Occupational Safety and Health Administration, OSHA, reduced the Permissible Exposure Limit (PEL) and created an Action Level (AL) for respirable crystalline silica (RCS) by half and will require engineering controlsto help mitigate employee exposure. In June 2018, the new RCS PEL of 0.05 mg/m3 averaged over an 8-hour period will apply to hydraulic fracturing and most other industries, and engineering control obligations will commence in June 2021 for hydraulic fracturing operations.
With an average of over one million pounds of silica sand used in horizontal well completions, crystalline silica is a major component of hydraulic fracturing. Multiple proppant transfer points can generate high concentrations of airborne dust, from offloading trucks to being pumped down hole. Engineering controls can be used tomitigate exposure.
A study was conducted at multiple hydraulic fracturing sites to determine if RCS concentrations could be reduced below OSHA's new PEL using engineering controls that do not have an onsite footprint, namely chemically pre-treated sand.During the study, 10 mm nylon Dorr-Oliver (DO) cyclones were used to measure the amount of RCS produced with and without the chemical engineering control in place. The results showed significant reductions in RCS in both personal and area sampling.
Results presented in this paper will show that effective engineering controls, withno footprint on site, exist and can significantly reduceair-borne RCS concentrations. Overall helping mitigate occupational exposures below the revised PEL and often below the Action Level.
Distance of Investigation for Unconventional Reservoirs Could be Misleading
Authors: Tabatabaie S. Hamed , Pooladi-Darvish Mehran , Mattar Louis 
Published: October 2017

Abstract
Distance of investigation equations are often used, explicitly or implicitly, in rate transient analysis. One important application is for estimation of distance to boundary and its use for well-spacing optimization. The concept of radius of investigation has been used successfully in conventional reservoirs, and has been extended to unconventional reservoirs. Here, we clearly demonstrate the inconsistencies that arise from such extension, and develop concepts and methodologies to remedy such inconsistencies. In particular, we confirm that in radial systems, infinite acting behavior as observed at the production well is consistent with infinite-acting behavior in the reservoir. In other words, i.e. deviation from straight-line behavior on specialized plots is observed shortly after a minimal amount of depletion has occurred at the far boundary. This makes use of the concept of radius of investigation straight forward; a concept that suggests there should be an insignificant pressure drop at the radius of investigation. However, this is not the case for linear flow. The transient behavior as observed in production data is NOT consistent with infinite-acting behavior in the reservoir. The deviation from straight-line behavior on specialized plots is observed much later than end of infinite acting in the reservoir, when there is significant depletion in the reservoir. We demonstrate how misleading it would be, if the concept of distance of investigation is extended to this situation. To remedy this, "time of detection" is introduced as a practical way of relating these theoretical concepts to the practical questions of determination of drainage area for well- and fracture-spacing applications. We demonstrate the use of these concepts through a couple of thought experiments.
Effect of Water in Trasnport and Storage of Non-Aqueous Species in Kerogen
Authors: Kazemi Mohammad , Takbiri-Borujeni Ali , Mansouri-Boroujeni Mahdi , Sun Ting 
Published: October 2017

Abstract
The objective for this work is to determine transport coefficients of multicomponent systems in atomistic kerogen models using molecular dynamics simulations. In transport of multicomponent gases, we are specifically interested in investigating the effects of nonmethane species (ethane, water, and carbon dioxide) on diffusion of methane. The kerogen unit models prepared by (Ungerer et al., 2014) are used in this study. Two mixtures, one containing water and one without water, are placed within the kerogen structures. Computed methane-methane diffusion coefficients are approximately one order of magnitude higher than those for other species in both mixtures for all kerogen types. This is due to fact that methane has the lowest adsorption compared with other three species, and therefore its Onsager diffusion coefficients are the highest. Among the other three species, ethane has the highest diffusion coefficients and water demonstrates the lowest Onsager coefficients. High adsorption (and low transport coefficients) of water is due to induced polarity of the pore surfaces that causes water molecules to be preferentially adsorbed to the pore surfaces over other species. Most of species demonstrate higher diffusion coefficients in the mixture containing water than in other mixture. In the absence of water molecules, vacant adsorption sites become available for other species. These sites will be preferably filled by carbon dioxide molecules as they have higher adsorption capabilities compared to alkanes.
Impact of Screen Geometry on Erosional Resistance of Direct Wire-Wrap Screens
Authors: McKeon C. Dalton , Nelson Seth M. , Gallo Federico , Mayer Christian 
Published: October 2017

Abstract
When estimating the erosion damage from passed fines through wire-wrap sand screens, variables such as approach velocity and gap velocity are often considered to be the main design considerations. Additional variables, such as the gap between the screen and base pipe, are often neglected. For the purpose of the experiments presented in this paper, two main objectives were defined. The first objective was to gain a better understanding of the location and progression of erosion in a conventional wire-wrap sand screen. In particular, inspection of the inlet and outlet surfaces of the screen was conducted in order to evaluate the erosion effects on both boundaries. The second objective was to evaluate the erosion effects of allowing flow to pass underneath the screen’s axial rib wires by introducing various standoff distances between the base pipe and the axial rib wires. The selected standoff distances were similar to a drainage layer typically included in metal-mesh type sand screens. To achieve these two objectives, eight experiments were conducted in an erosion test flow loop with varying experimental standoff geometry stack-ups. Any damage to the sand screen was quantified by calculating the specific erosion of the screen, which is the screen’s total mass loss divided by the total mass of particles passed for a given test duration. Photographs of the coupons before and after each test were used to qualitatively identify affected areas of erosion. The results of these experiments and a brief description of the testing approach are provided herein.
An Experimental Study of Non-Equilibrium CO2-Oil Interactions
Authors: Yassin Mahmood Reza , Habibi Ali , Eghbali Sara , Zolfaghari Ashkan , Dehghanpour Hassan 
Published: October 2017

Abstract
In this study, we use a custom-designed visual cell to investigate non-equilibrium CO2/oil interactions under high-pressure and high-temperature conditions. We visualize the CO2/oil interface and measure visual cell's pressure over time. We perform 5 sets of visualization test. The first three tests aim at investigating interactions of gaseous (g), liquid (l), and supercritical (sc) CO2 with the Montney oil. In the fourth test, in order to visualize the interactions at the bulk oil phase, we replace the opaque Montney oil with a translucent Duvernay light oil (LO). Finally, we conduct N2(sc)-Oil test to compare the results with those of CO2-Oil tests.
Results of the first three tests show that oil immediately expands upon injection of CO2 into the visual cell. CO2(sc) leads to the maximum oil expansion followed by CO2l and CO2(g). Furthermore, the rate of oil expansion in CO2(sc)-Oil test is higher than that in CO2(l)-Oil and CO2(g)-Oil tests. We also observe extracting and condensing flows at the CO2(l)-Oil and CO2(sc)-Oil interfaces. Moreover, we observe density-driven fingers inside the LO phase due to the local increase in the density of LO. We do not observe neither extracting/condensing flows nor density-driven mixing for N2(sc)-Oil and CO2(g)-Oil tests, explaining low expansion of oil in these tests. The results suggest that the combination of density-driven natural mixing and extracting/condensing flows enhance CO2(sc) dissolution into the oil phase, leading to fast oil expansion after CO2(sc) injection into the visual cell.
A Mechanism Study of Wettability and Interfacial Tension for EOR Using Silica Nanoparticles
Authors: Jiang Renfeng , Li Kewen , Horne Roland 
Published: October 2017

Abstract
Wettability alteration and interfacial tension (IFT) reduction are two important mechanisms for enhanced oil recovery (EOR). The introduction of nanotechnology from the fields of Biology and Material Science to the application in EOR is emerging because nanoparticles have the potential to alter formation factors like wettability and fluid properties like IFT and viscosity. However, a systematic literature review shows that ambiguity exists regarding whether nanoparticles can change wettability and IFT or not and which component in nanofluid plays a role. In this work, we investigated the effects of bare silica nanoparticles on wettability and IFT using a contact angle goniometer. The results showed that the contact angle measurement on quartz plates had relatively large uncertainty while those on calcite plates showed a clear trend that the smaller the nanoparticle size and the larger the nanofluid concentration, the smaller the contact angle. In addition, silica nanoparticles did not have an effect on IFT. Core flooding experiments showed an increase of 8.7% in oil recovery factor by the use of silica nanoparticles, which support the oil recovery mechanism of wettability alteration.
Securing Long-Term Well Productivity of Horizontal Wells Through Optimization of Postfracturing Operations
Authors: Potapenko D. I. , Williams R. D. , Desroches J. , Enkababian P. , Theuveny B. , Willberg D. M. , Moncada K. , Deslandes P. , Wilson N. , Neaton R. , Mikovich M. , Han Y. , Conort G. 
Published: October 2017

Abstract
Poststimulation operations on multistage hydraulically stimulated horizontal wells producing from conventional and unconventional reservoirs have a major impact on long-term well performance. Most common types of poststimulation services on such wells include plug drillout (PDO) operations and well flowback (WFB) operations. During these operations, the hydraulic fracture system experiences major changes in pressure and flowrate, which may affect the well's long-term productivity. Among the many mechanisms responsible for decrease in well productivity, we highlight 1) the risk of losing the connection between the wellbore and hydraulic fracture system because of the development of an unpropped area; 2) rock destabilization, and 3) the risk of scaling and precipitation.
In this paper, we describe an integrated engineering and operations workflow for optimizing poststimulation operations on horizontal wells by controlling the productive fracture system evolution during the poststimulation period. The approach is based on applying the secure operating envelope (SOE) concept, which provides a set of operating parameters that ensure preservation of the connection between the hydraulic fractures and wellbore. The SOE is defined for each individual well, using a combination of geomechanical and multiphase transport modeling. It accounts for reservoir properties, well completion, and fracture treatment parameters. High-resolution, real-time monitoring of well performance and active control of bottomhole conditions through choke management ensure the well is operated within the SOE. The production objectives combined with the evolution of the SOE enable an overall strategy for poststimulation operations.
The paper outlines how the SOE is constructed. Applications of the proposed approach on horizontal oil and gas wells in unconventional reservoirs in North America are reported, both during well flowback and plug drillout operations. Using the SOE during well flowback helps to predict and avoid a decrease in well production performance caused by excessive proppant flowback which results in creation of near-wellbore pinch points inside hydraulic fractures. Additionally, plug drillout was identified as a critical operation, during which the proppant pack can be destabilized. The associated risk was strongly reduced by applying the SOE concept in combination with high-resolution monitoring.
Based on data obtained from more than 50 operated wells, we conclude that the proposed methodology, including application of geomechanical modeling to poststimulation operations, brings significant opportunities for optimization of well performance and securing long-term well productivity.