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Guest Editorial

J. Energy Resour. Technol. 2017;139(2):020301-020301-1. doi:10.1115/1.4036042.
FREE TO VIEW

The editor and editorial board of the ASME Journal of Energy Resources Technology would like to thank all of our reviewers for volunteering their expertise and time reviewing manuscripts in 2016. We are grateful to all of our reviewers for contributing to the advancement of the science and technology of Mechanical and Petroleum Engineering for the benefit of humanity. Below is a complete list of reviewer’s for 2016. We would also like to acknowledge two outstanding reviewers of the year.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2016;139(2):022001-022001-9. doi:10.1115/1.4034025.

Finding optimal operating conditions of solar-based power and cooling systems is always a challenge. Performance of these systems is highly dependent on several important parameters, which influence not only the long-term efficiency but also its technical and economic feasibility. This paper studies the operation/configuration problem of an ammonia–water power and cooling cycle using an exergetic and statistical analysis. The Modeling developed in Matlab® and REFPROP 9.0 was used to calculate the thermodynamic properties of the ammonia–water mixture. The thermodynamic model and properties of the ammonia/water mixture were validated with previous models found in the literature. Optimal operating conditions of the combined cycle were obtained by using response surface technique and the ratio between exergetic efficiency and exergy destruction was used as response variable. The results showed that the response variable is highly influenced by the ammonia concentration, pressure ratio (PR), turbine efficiency, and pinch point temperature in the heat exchanger. Finally, the combined cycle was integrated with a solar field using two types of concentrated solar collectors.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022002-022002-10. doi:10.1115/1.4034229.

Waste heat driven ammonia/water Kalina cycles have shown promise for improving the efficiency of electricity production from low-temperature reservoirs (T < 150 °C). However, there has been limited application of these systems to utilize widely available, disperse, waste heat streams for smaller scale power production (1–10 kWe). Factors limiting increased deployment of these systems include large, costly heat exchangers, and concerns over safety of the working fluid. The use of mini- and microchannel (D < 1 mm) heat exchangers has the potential to decrease system size and material cost, while also reducing the working fluid inventory, enabling penetration of Kalina cycles into these new markets. However, accurate methods of predicting the heat and mass transfer in microscale geometries must be available for designing and optimizing these compact heat exchangers. In the present study, the effect of different heat and mass transfer models on the calculated Kalina cycle condenser size is investigated at representative system conditions. A detailed heat exchanger model for a liquid-coupled microchannel ammonia/water condenser is developed. The heat exchanger is sized using different predictive methods to provide the required heat transfer area for a 1 kWe Kalina system with a source and sink temperature of 150 °C and 20 °C, respectively. The results show that for the models considered, predicted heat exchanger size can vary by up to 58%. Based on prior experimental results, a nonequilibrium approach is recommended to provide the most accurate, economically sized ammonia/water condenser.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022003-022003-10. doi:10.1115/1.4034289.

Complete quantitative data of the chemical (proximate, ultimate, and ash analyses) and mineral (in low-temperature ash (LTA) and various high-temperature ashes (HTA)) compositions of 21 coals were used to investigate the modes of occurrences and high-temperature behaviors of the minerals in coals and their influence on ash fusibility. The common minerals present in the low-temperature ashes (LTA) are kaolinite, quartz, muscovite, calcite, gypsum, pyrite, and siderite. The samples were divided into two groups according to the hemispherical temperature for a comparative study of the behavior of mineral matters. Results show that the average number of mineral species (ANMS) and amorphous substances (AS) in the LTAs of the two groups are essentially the same. The ANMS in both the low and high (ash fusion temperatures, AFT) ash samples go through the same tendency of a slight reduction at first, an increase, and finally, a significant reduction. As the temperature increases, the ANMS in the low-AFT ash is initially higher and then lower than the high-AFT ash, whereas the tendency of the AS is quite the opposite. The ash melting process is divided into three stages, and the AFTs are related to different degrees of the eutectic stage.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022004-022004-9. doi:10.1115/1.4034232.

Heavy duty gas turbines are the core components in the integrated gasification combined cycle (IGCC) system. Different from the conventional fuel for gas turbine such as natural gas and light diesel, the combustible component acquired from the IGCC system is hydrogen-rich syngas fuel. It is important to modify the original gas turbine combustor or redesign a new combustor for syngas application since the fuel properties are featured with the wide range hydrogen and carbon monoxide mixture. First, one heavy duty gas turbine combustor which adopts natural gas and light diesel was selected as the original type. The redesign work mainly focused on the combustor head and nozzle arrangements. This paper investigated two feasible combustor arrangements for the syngas utilization including single nozzle and multiple nozzles. Numerical simulations are conducted to compare the flow field, temperature field, composition distributions, and overall performance of the two schemes. The obtained results show that the flow structure of the multiple nozzles scheme is better and the temperature distribution inside the combustor is more uniform, and the total pressure recovery is higher than the single nozzle scheme. Through the full scale test rig verification, the combustor redesign with multiple nozzles scheme is acceptable under middle and high pressure combustion test conditions. Besides, the numerical computations generally match with the experimental results.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022005-022005-8. doi:10.1115/1.4034640.

In this study, the analysis of energy and exergy of a horizontal axis wind turbine based on blade element momentum (BEM) theory is presented. The computations are validated against wind tunnel data measured in the MEXICO wind turbine experiment. Blade roughness as one of the important environmental parameters is considered in the computations. Results show that the blade element momentum (BEM) theory has good ability to predict the energy and exergy efficiencies. The computation of energy and exergy exhibits that with the increasing the roughness from 0 mm to 0.5 mm, 2324 W of the output power is reduced. Roughness of 0.5 mm at the wind speed of 16 m/s reduced exergy and energy efficiencies 5.75% and 5.83%, respectively. It is also found that the roughness in the first four months of the operation has a more negative effect on the wind turbine performance.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2016;139(2):022201-022201-11. doi:10.1115/1.4034026.

This paper analyzes the feasibility of applying model predictive control strategies for mitigation of the auto-ignition phenomenon, which affects the performance of spark-ignition internal combustion engines. The first part of this paper shows the implementation and experimental validation of a two-dimensional model, based on thermodynamic equations, to simulate operating conditions in engines fueled with natural gas. Over this validated model, several control strategies are studied in order to evaluate, through simulation analysis, which of these offer the best handling capacity of the auto-ignition phenomenon. In order to achieve this goal, multivariate control strategies are implemented for a simultaneous manipulation of the fuel/air ratio, the crank angle at ignition, and the inlet pressure. The controlled variable in this research is the temperature at the ignition point. This temperature is obtained through an estimation based on pressure in the combustion chamber at that point, which is located toward the end zone of the compression stroke. If the ignition temperature of the fuel–air mixture is reached during the compression process, then auto-ignition takes place. Proposed control strategies consist of maintaining the temperature in the ignition point below the fuel–air mixture auto-ignition temperature. The results show that auto-ignition is difficult to avoid using a single input–single output (SISO) strategy. However, a multiple input–single output (MISO) approach avoids the influence of the phenomenon without a significant impact over the engine's performance. Among the developed strategies, an approach based on model predictive control and feedforward control strategy shows the best performance, measured through the integral absolute error (IAE) index. These results open the possibility of new ways for improving the control capacity of auto-ignition phenomenon in engines compared to currently available feedback control systems.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022202-022202-6. doi:10.1115/1.4033984.

Gas-to-liquid (GTL), an alternative synthetic jet fuel derived from natural gas through Fischer–Tropsch (F–T) process, has gained significant attention due to its cleaner combustion characteristics when compared to conventional counterparts. The effect of chemical composition on key performance aspects such as ignition delay, laminar burning speed, and emission characteristics has been experimentally studied. However, the development of chemical mechanism to predict those parameters for GTL fuel is still in its early stage. The GTL aviation fuel from Syntroleum Corporation, S-8, is used in this study. For theoretical predictions, a mixture of 32% iso-octane, 25% n-decane, and 43% n-dodecane by volume is considered as the surrogate for S-8 fuel. In this work, a detailed kinetics model (DKM) has been developed based on the chemical mechanisms reported for the GTL fuel. The DKM is employed in a constant internal energy and constant volume reactor to predict the ignition delay times for GTL over a wide range of temperatures, pressures, and equivalence ratios. The ignition delay times predicted using DKM are validated with those reported in the literature. Furthermore, the steady one-dimensional premixed flame code from CANTERA is used in conjunction with the chemical mechanisms to predict the laminar burning speeds for GTL fuel over a wide range of operating conditions. Comparison of ignition delay and laminar burning speed shows that the Ranzi et al. mechanism has a better agreement with the available experimental data, and therefore is used for further evaluation in this study.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022203-022203-10. doi:10.1115/1.4034230.

Microexplosion behavior of water in biodiesel emulsion droplets was studied by suspending a single droplet on a wire type thermocouple. Water in biodiesel emulsion droplets with 9%, 12%, 15%, and 18% water by volume was observed in the Leiden frost regime using a hot plate as the heat source maintained at two different temperatures of 400 °C and 500 °C. The evolution of microexplosion was recorded with a high-speed camera synchronized with a temperature data logger. The emulsions were prepared by an electrical stirrer fitted with customized made blades rotating at 1500 rpm for 15 min. The emulsions were stabilized with two different hydrophilic–lipophilic balance (HLB) values, which were prepared by mixing two different commercial surfactants. It is found that the microexplosion time and temperature were influenced by emulsion stability, water content, surfactant dosage, base plate temperature, and HLB value. All the unstable emulsions developed microexplosion at both plate temperatures. Emulsions stabilized with an HLB value of 6.31 and 18% water content did exhibit microexplosion at both base plate temperatures. Also, the waiting time was found to decrease with increasing surfactant concentrations for a 500 °C plate temperature compared to 400 °C.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022204-022204-11. doi:10.1115/1.4034288.

Aftermarket dual-fuel injection systems in diesel engines using hydrous ethanol as secondary fuel have been developed as a means to lower emissions from older diesel-powered equipment. However, our previous work has shown that the emissions benefits of currently available aftermarket intake fumigation injection systems can be inconsistent with manufacturer claims. Our current study evaluates a newly developed aftermarket dual-fuel system that incorporates a fuel heating system and port fuel injection (PFI). This paper describes an experimental investigation of engine-out emissions from a John Deere 4045HF475 Tier 2 engine with port injection of 180 proof (90% ethanol by volume) hydrous ethanol. The engine was retrofitted with a custom fuel heat exchanger to heat the hydrous ethanol to a range of 46–79 °C for helping to improve fuel vaporization in the intake port. PFI duration was controlled using engine speed and throttle position as inputs to achieve a desired fumigant energy fraction (FEF), defined as the amount of energy provided by the hydrous ethanol based on lower heating value (LHV) over the total fuel energy provided to the engine. Data was collected over a range of FEF with direct injected diesel for eight operating modes comparing heated versus unheated hydrous ethanol. Results of the study indicate that as FEF increases, NO emissions decrease, while NO2, CO, THC, and unburned ethanol emissions increase. In addition, it was found that preheating the ethanol using engine coolant prior to injection has little benefit on engine-out emissions. The work shows that the implemented aftermarket dual-fuel PFI system can achieve FEF rates up to 37% at low engine load while yielding modest benefits in emissions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022205-022205-8. doi:10.1115/1.4035149.

A bluff body burner was investigated using computational fluid dynamics (CFD) to assess the effects of inlet turbulence intensity and compare the combustion characteristics with and without the bluff-body modeled in the computational domain. The effects of the CFD modeling techniques were assessed for inlet turbulence intensity, using a two-dimensional (2D) versus three-dimensional (3D) computational domain, and whether to include the bluff body in the domain. The simulations were compared with experimental data from the Turbulent Nonpremixed Flames workshop. The results showed that the turbulence intensity specified as a boundary condition at the fuel-jet inlet had a substantial impact on the axial decay of mixture fraction and temperature, which was overlooked by previous researchers when the bluff body was not modeled. The numerical results of the 2D axisymmetric and 3D domains without the bluff body showed that the 3D domain provided the best predictions when the turbulence intensity was defined using a published correlation versus experimental estimates since the k–ε turbulence model underestimated dissipation. It was shown that a 2D axisymmetric domain can be used to obtain predictions with acceptable numerical errors without the inclusion of the bluff body, and that a uniform inlet velocity can be specified, provided that the inlet turbulence intensity is defined using the correlation by Durst et al. (“Methods to Set Up and Investigate Low Reynolds Number, Fully Developed Turbulent Plane Channel Flows,” ASME J. Fluids Eng., 120(3), pp. 496–503.). Finally, further analysis of flow and flame characteristics demonstrated that when the bluff-body was included for the 2D axisymmetric domain, predictions improved and the flow was insensitive to inlet turbulence intensities because the bluff-body provided an entrance region for the flow to develop before mixing, thus reducing inlet effects. Thus, if experimental inlet data are not available, the addition of the bluff-body in the computational domain provides a more accurate jet velocity profile entering the reacting domain and eliminates errors caused by the inlet boundary condition.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022206-022206-8. doi:10.1115/1.4035256.

In order to design energy efficient cooker-top burners, the stabilization mechanisms of partially premixed flames were investigated. Different design features are assessed with the identical fuel (CH4), fuel flow rate, and load vessel arrangement, but with different levels of primary aeration and flame delivery. k–ε Reynolds-averaged Navier–Stokes (RANS) simulations are performed using the modified temperature-composition pdf method and the intrinsic low-dimensional manifold (ILDM) reduction scheme. The results show that the optimum value of the angle of flame delivery is about 30–35 deg. The contact area of the flame cup under the bottom surface depends on the diameter of the burner head which determines the separation of the flames. The traditional solution to reduce the port separations, which is to increase the number of ports, is shown to cause weak flames which extinguish in shorter distances and can have strong tendency to blow off. It also causes significant pressure resistance ahead of the contraction tube and so impairs the primary aeration. In the present study, a new slot profile, named the double-V form, is proposed and shown to be very effective in reducing the gaps between the flames, without creating any further pressure resistance.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2016;139(2):022903-022903-7. doi:10.1115/1.4033591.

One of the most critical aspects in the drilling operation is to reduce the nonproductive time and to avoid the borehole instability issues such as kicks, blow outs, lost circulation, stuck pipe, and breakouts. To investigate these problems, one has to understand the formation properties, fluid hydraulics, and the basic mechanics behind drilling a well. In the previous research on this field, the factors were widely discussed and results obtained were related to the formation properties. However, while considering the stresses in the wellbore, the mechanical factors such as the RPM and contact of casing at different positions in wellbore have usually been neglected. In furtherance to this study, the importance of thermal condition, fluid loss, and filter cake formation study cannot be out ruled. This work includes a new insight toward understanding the stress redistribution due to pipe contact by the wellbore and smear mechanism. Additionally, it presents the numerical analysis of influence of casing contact and downhole thermal conditions using the finite-element analysis. The classical equations used to obtain the wellbore stresses include very few parameters such as the far-field stresses, pore pressure, and wellbore geometry. They do not consider the influence of casing contact while drilling, mud-cake permeability, and elastic and inelastic properties of the formation. To take into account the effects of these parameters, finite-element analysis is carried out considering the above-mentioned parameters in various scenarios. The main objective of these simulations is to investigate the hypothesis of the increase in hoop stress considering casing contact with regard to formation stresses orientation. The study of different cases shows the variation of a few hundred psi of hoop stress. However, the thermal effect on the near-wellbore stress regions can be important for drilling in deep water and other complex drilling environments. To see the thermal effect, this study develops a thermoporoelastic model. It is found that there is decrease in radial stress and hoop stress in near-wellbore region with time. This reduction will have a considerable impact on fracture initiation pressure in the near-wellbore region. Also, the smearing effect will be influenced by stress changes due to change in temperature.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022901-022901-15. doi:10.1115/1.4033982.

By treating heavy oil as multiple pseudocomponents, techniques have been developed to experimentally and theoretically determine diffusion coefficients of CO2-heavy oil systems by coupling heat and mass transfer together with consideration of swelling effect. Experimentally, diffusion tests have been conducted for hot CO2-heavy oil systems with three different temperatures under a constant pressure by using a visualized pressure-volume-temperature (PVT) setup. The swelling of liquid phase in the PVT cell is continuously monitored and recorded during the measurements. Theoretically, a two-dimensional (2D) mathematical model incorporating the volume-translated Peng–Robinson equation of state (PR EOS) with a modified alpha function has been developed to describe heat and mass transfer for hot CO2-heavy oil systems. Heavy oil sample has been characterized as three pseudocomponents for accurately quantifying phase behavior of the CO2-heavy oil systems, while the binary interaction parameters (BIPs) are tuned with the experimentally measured saturation pressures. The diffusion coefficient of hot CO2 in heavy oil is then determined once the discrepancy between the experimentally measured dynamic swelling factors and theoretically calculated ones has been minimized. During the diffusion experiments, heat transfer is found to be dominant over mass transfer at the beginning and reach its equilibrium in a shorter time; subsequently, mass transfer shows its dominant effect. The enhanced oil swelling mainly occurs during the coupled heat and mass transfer stage. CO2 diffusion coefficient in heavy oil is found to increase with temperature at a given pressure, while it can be explicitly correlated as a function of temperature.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022902-022902-9. doi:10.1115/1.4034069.

This research developed a viable and economical foaming formula (AOS/AVS/N70K-T) which is capable of creating ample and robust CO2 foams. Its foaming ability and displacement performance in a porous medium were investigated and compared with the two conventional formulations (AOS alone and AOS/HPAM). The results showed that the proposed formula could significantly improve the foam stability without greatly affecting the foaming ability, with a salinity level of 20,000 ppm and a temperature of 323 K. Furthermore, AOS/AVS/N70K-T foams exhibited thickening advantages over the other formulations, especially where the foam quality was located around the transition zone. This novel formulation also showed remarkable blocking ability in the resistance factor (RF) test, which was attributed to the pronounced synergy between AVS and N70K-T. Last but not the least, it was found that the tertiary oil recovery of the CO2 foams induced by AOS/AVS/N70K-T was 12.5% higher than that of AOS foams and 6.8% higher than that of AOS/HPAM foams at 323 K and 1500 psi, thus indicating its huge enhanced oil recovery (EOR) potential. Through systematic research, it is felt that the novel foaming formulation might be considered as a promising and practical candidate for CO2 foam flooding in the future.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022904-022904-7. doi:10.1115/1.4034291.

A high pressure single polycrystalline diamond compact (PDC) cutter testing facility was used to investigate the effect of five factors on PDC cutter performance on Alabama marble. The factors include: depth of cut (DOC), rotary speed, back rake angle, side rake angle, and confining (wellbore) pressure. The performance is quantified by two parameters: mechanical specific energy (MSE) and friction angle. Fractional factorial design of experiments methodology was used to design the experiments, enabling detection of potential interactions between factors. Results show that, in the range tested, the only statistically significant factor affecting the MSE is DOC. In other words, DOC's influence is predominant and it can mask the effect of all the other factors. These results could have applications in real time pore pressure detection. Further, the results show that back rake angle is the most statistically significant factor in friction angle. Side rake angle and depth of cut also affect the friction angle, but in a relatively unimportant manner. The MSE–DOC behavior is explained and modeled by cutter edge–groove friction and the circular cutter shape. It is speculated that high cutter edge friction overwhelms the actual cutting process. A comparison of five currently present models in the literature with these results is presented and the conclusion is that the future PDC cutter models should digress from the traditional shear failure plane models.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022905-022905-9. doi:10.1115/1.4034443.

History matching is essential for estimating reservoir performances and decision makings. Ensemble Kalman filter (EnKF) has been researched for inverse modeling due to lots of advantages such as uncertainty quantification, real-time updating, and easy coupling with any forward simulator. However, it requires lots of forward simulations due to recursive update. Although ensemble smoother (ES) is much faster than EnKF, it is more vulnerable to overshooting and filter divergence problems. In this research, ES is coupled with both clustered covariance and selective measurement data to manage the two typical problems mentioned. As preprocessing work of clustered covariance, reservoir models are grouped by the distance-based method, which consists of Minkowski distance, multidimensional scaling, and K-means clustering. Also, meaningless measurement data are excluded from assimilation such as shut-in bottomhole pressures, which are too similar on every well. For a benchmark model, PUNQ-S3, a standard ES with 100 ensembles, shows severe over- and undershooting problem with log-permeability values from 36.5 to −17.3. The concept of the selective use of observed data partially mitigates the problem, but it cannot match the true production. However, the proposed method, ES with clustered covariance and selective measurement data together, manages the overshooting problem and follows histogram of the permeability in the reference field. Uncertainty quantifications on future field productions give reliable prediction, containing the true performances. Therefore, this research extends the applicatory of ES to 3D reservoirs by improving reliability issues.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022906-022906-9. doi:10.1115/1.4034548.

As coal has strong adsorption characteristics and well-developed natural fracture systems, an improper choice of fracturing fluid can result in significant challenges for coal bed methane exploitation, including damage to the coal formation and ineffective creation and propagation of hydraulic fractures. Viscoelastic surfactant (VES) fracturing fluid has become a preferred option because of its easy flowback and the resultant minimal damage. A novel nanocomposite fiber with substantially improved functional and structural properties was synthesized by introducing nanoparticles into conventional polyester fiber. Subsequently, a nanocomposite fiber-laden VES (NFVES) fracturing fluid was developed and evaluated in the laboratory. The results show that the fiber disperses well in the fluid and that the addition of a small amount (0.5%) of fiber substantially enhances the proppant-carrying capacity of the fluid. To achieve a proppant-carrying capacity equivalent to a standard VES, the surfactant concentration can be decreased from 2.5% to 1%, which not only reduces costs but also significantly lowers adsorption of the surfactant by the seam and rock surfaces. In addition, rod micelles with less surfactant added are more easily broken. Addition of 0.7% nanocomposite fiber reduced the tube friction by 20% at shearing rate of 5000 s−1. The nanocomposite fiber also effectively prevents backflow of the proppant and mitigates leak-off of fluid and aggregation of coal scraps. Continuous degradation of the fiber occurs over time at formation temperatures, thus reducing the potential damage to the coal seam. The strong performance of this NFVES fracturing fluid in the laboratory evaluations indicates the great potential and development prospects for coal bed methane reservoir stimulation using this fluid.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022907-022907-9. doi:10.1115/1.4034905.

The subject of this experimental report is the application of nanoparticles in petroleum refining. Sulfur removal from petroleum using carbon nanotubes is considered in this study. The properties related to the process characterization are measured experimentally and reported. The effect of low range temperature and pressure, initial concentration, interfacial velocity, the ratio of height to diameter of the bed and particle diameter on the outlet sulfur is investigated. Design of experiment is performed to show which of the controllable parameters affects the sulfur removal process and a predictive model is developed. Optimization of the model is performed with the aim that the outlet sulfur content less than 0.6 ppm is achievable. Also, the increase in the amount of pollutant higher than 50 ppm sulfur and increase in the amount of superficial velocity higher than 0.4 m/s lead the adsorption process to the improper results. Finally, cost estimation due to pressure and temperature is presented and the optimum conditions of 1.7 atm pressure and 35 °C temperature with the height to diameter ratio of three and nano carbon tubes of 50 nm for packed bed are proposed.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2016;139(2):022908-022908-11. doi:10.1115/1.4035150.

A mechanistic model has been developed and validated to quantify a single gas bubble growth with considering multicomponent gas diffusion in solvent(s)–CO2–heavy oil systems under nonequilibrium conditions. Experimentally, constant-composition expansion (CCE) experiments are conducted for C3H8–CO2–heavy oil systems under equilibrium and nonequilibrium conditions, respectively. Theoretically, the classic continuity equation, motion equation, diffusion–convection equation, real gas equation, and Peng–Robinson equation of state (PR EOS) are integrated into an equation matrix to dynamically predict gas bubble growth. Also, the viscous term of motion equation on the gas phase pressure is included due mainly to the viscous nature of heavy oil. The newly proposed model has been validated by using the experimentally measured gas bubble radius as a function of time with good accuracy. Combining with the experimental measurements, the critical nucleus radius and gas bubble growth are quantitatively predicted with the newly proposed model. Effects of mass transfer, supersaturation pressure, mole concentration of each component, liquid cell radius, and pressure decline rate on the gas bubble growth are examined and analyzed. In general, gas bubble growth rate is found to increase with an increase of each of the aforementioned five parameters though the contribution of individual component in a gas mixture to the bubble growth rate is different. A one-step pressure drop and the unlimited liquid volume surrounding a gas bubble are considered to be the necessary conditions to generate the linear relationship between gas bubble radius and the square root of time.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(2):022912-022912-8. doi:10.1115/1.4035425.

In real time drilling, the complexity of drilling fluid filtration is majorly attributed to changing mud rheology, formation permeability, mud particle size distribution (PSD), filter cake plastering effects, and geochemical reaction of particles at geothermal conditions. This paper focuses on quantifying the major effects as well as revealing their contribution toward effective wellbore stabilization in sandstone formations. We conducted an extensive experimental and analytical study on this subject at different levels. First, we used field application and the results as guides for our experiments. We have considered both oil-based mud and water-based mud. Next, we optimized the mud particle size distribution (PSD) by carefully varying the type, size, and concentration of wellbore strengthening material (WSM). Laboratory high pressure high temperature fluid loss tests were carried out on Michigan and Bandera Brown sandstones. The results from these tests identify the formation heterogeneity and permeability in successful wellbore stabilization. Filter cake permeability calculations, using the analytical model for linear systems, were consistent with filtration rates, and the expected trend of permeability declines with time. Finally, we investigated the evolution of internal filter cake and plastering mechanism, using scanning electron microscopic (SEM) analysis. The test results revealed a significant difference in the formation permeability impairment for the optimal mud PSD and WSM blend.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(2):022913-022913-7. doi:10.1115/1.4035426.

Disasters such as offshore oil spills will have a significant negative impact on occupations, incomes, tariffs, and further profits, adding to the struggles of regional area held up in difficulty. Such a broad size of impact can more impair the functioning of the economy of the district. In addition to costs encountered by cleanup activities, industries and individuals dependent on coastal resources can experience huge economic losses. Many other related businesses and sectors can possibly hurt by disruptions and loss of earnings. To better understand different aspects of the problem, we explain the problem through a case study for recent incident in the Gulf of Mexico (GoM), the Deepwater Horizon oil spill (DWH) on April 20, 2010, the worst oil spill disaster in the history of the U.S. start off the coastline of Louisiana in the Gulf of Mexico. We have conducted study to focus on the positive impact of economic compensation on Gulf coast employment and wages. Regardless of estimates of main job losses resulting from the oil spill, we estimated that Louisiana experienced a net rise in employment and wages. Input–output (I-O) model will be applied in this study to approximate the economic compensation created by economic injection due to the Deepwater Horizon accident. Then, we can estimate the gross damages to the Louisiana economy. More importantly, the final results should provide useful information on measuring the economic impact of any future large-scale disasters and for how companies must react to minimize the economic impact of events. One positive side that will come out of the oil spill is the spotlight on the need for new and developed prevention and response strategies to this kind of major disasters. The analysis of losses in the employment and earnings in Louisiana in the aftermath of accidents in petroleum industry makes to know the importance and significance of the oil and gas sector as a powerful economic machine that provides a wide range of opportunity for the state. It is no surprise how remarkable is the influence of oil and gas industry on the income of the state workers and the output of the state. Therefore, having approximation of the impact helps to facilitate strong recovery and to prevent potential harm to the related industry.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(2):022911-022911-10. doi:10.1115/1.4035515.

Reservoir characterization is a process of making models, which reliably predict reservoir behaviors. Ensemble Kalman filter (EnKF) is one of the fine methods for reservoir characterization with many advantages. However, it is hard to get trustworthy results in discrete grid system ensuring preservation of channel properties. There have been many schemes such as discrete cosine transform (DCT) and preservation of facies ratio (PFR) for improvement of channel reservoirs characterization. These schemes are mostly applied to 2D cases, but cannot present satisfactory results in 3D channel gas reservoirs with an aquifer because of complex production behaviors and high uncertainty of them. For a complicated 3D channel reservoir, we need reliable initial ensemble members to reduce uncertainty and stably characterize reservoir models due to the assumption of EnKF, which regards the mean of ensemble as true. In this study, initial ensemble design scheme is suggested for EnKF. The reference 3D channel gas reservoir system has 200 × 200 × 5 grid system (250 × 250 × 100 ft for x, y, and z, respectively), 15% porosity, and two facies of 100 md sand and 1 md shale. As the first step, it samples initial ensemble members, which show similar water production behaviors with the reference. Then, grid points are randomly selected for high and low 5% from the mean of sampled members. As a final step, initial ensemble members are remade using the selected data, which are assumed as additional known data. This proposed method reliably characterizes 3D channel reservoirs with an aquifer.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(2):022909-022909-13. doi:10.1115/1.4035513.

Scaling criteria have been developed and validated to evaluate performance of waterflooding and immiscible CO2 flooding in heavy oil reservoirs by using a three-dimensional (3D) sandpacked displacement model. Experimentally, the 3D physical model consisting of a pair of horizontal wells together with five vertical wells is used to conduct waterflooding and immiscible CO2 flooding processes, respectively. Theoretically, mathematical formulae have been developed for waterflooding and immiscible CO2 flooding by performing dimensional and inspectional analyses. The scaling group of the gravitational force to viscous force is found to be negligible when scaling up a model to its prototype. The relaxed scaling criteria are validated by comparing the simulation results of a synthetic reservoir with experimental measurements and then extended for a field application. There also exists a reasonably good agreement between the laboratory measurements and the field application with the determined scaling criteria.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;139(2):022910-022910-7. doi:10.1115/1.4035514.

Simulation techniques are increasingly becoming popular in recent years as a way of simulating oil drilling processes. Among them, directional drilling is a specific method that benefits enormously from such numerical techniques, inasmuch as the estimation of the wellbore curvature is crucial and cannot be properly estimated through approximate geometry methods. We present here some of the latest advances in bit contact dynamics, wellbore update algorithms, and experimental validation of side cutting, in the context of a finite element (FE) and finite segment simulation framework. The framework is based on the high-fidelity dynamic simulation of the mechanical system, including detailed geometry, large displacements, and accurate contact forces. The theoretical aspects, along with the experimental results, are thoroughly presented. Overall, this paper constitutes a step toward a more deterministic way of calculating build rates and designing downhole drilling tools.

Commentary by Dr. Valentin Fuster

Expert View

J. Energy Resour. Technol. 2016;139(2):024701-024701-3. doi:10.1115/1.4034290.

The United States of America government determines the guidelines for daily diet of humans in their various life stages. The current guidelines for caloric intake are about 2800 kcal daily for the adult male, and about 600 kcal less for the adult female. This work brings up the point that with the growing diversity of the population, these caloric intake guidelines need to consider the effect of temperature at the time the food is consumed. The motivation of this study is diversity; it is recognized that the Chinese and South Korean cuisines typically have high temperatures when served, whereas much of the standard American fare is consumed at room temperature. The thermal capacity of the foods consumed has not been taken into consideration. It is likely that the “empty” calories related to consumption of hot foods are helpful, in keeping the body warm without the risk of weight gain. It is suggested that they may also be used judiciously to lose weight.

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