Research Papers: Alternative Energy Sources

J. Energy Resour. Technol. 2019;141(9):091201-091201-8. doi:10.1115/1.4043133.

This paper presents the effect of the front surface water cooling on performance parameters (solar cell temperature, back surface temperature, outlet water temperature, electrical efficiency, overall efficiency, etc.) of photovoltaic/thermal (PV/T) module in both winter and summer seasons in Indian climatic conditions. A mathematical model of PV/T module considering energy balance equations has also been presented. A comparative analysis of performance parameters obtained analytically and experimentally has also been presented. A fair agreement has also been found between analytical and experimental results which is supported by correlation coefficient of approximately unity and root mean square error of 10–14%. By front surface water cooling, solar cell and back surface temperature of PV/T module have been found to decrease considerably which in turn resulted in enhanced electrical and overall efficiency of module in winter and summer seasons.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):091202-091202-12. doi:10.1115/1.4043134.

Centrifugal compressors have broad applications in gas compression processes, especially in automobile turbocharger. During the turbocharger installation, there are many installation limitations in the compressor stage. Due to the restriction in the size of the engine bay, it always has limitations of installation for turbochargers. The compressor package always requests to modify the compressor geometry to fit specific constraints. The volute is the largest geometry of the turbocharger package in most of the case. Very often modifications of the volute were performed to meet the space constraints. In this study, the authors investigated the compressor performance for an initially designed volute and a modified volute. The study followed by an on engine performance comparisons, compressor performance gas stand tests and computational fluid fynamics (CFD) analysis. The studies provided the performance impacts of the local volute deformation due to installation constraints, i.e., a kink in a volute. The studies showed the local volute kink has small implications on compressor performance when the maximum kink depth is less than 10% of the local volute hydraulic diameter. The numerical analysis is in favorable agreements with experiments. The results of this study can be used as a basic guideline for local deformation performance impacts for the future turbocharger compressor volute modifications.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2019;141(9):092001-092001-9. doi:10.1115/1.4043135.

Electrical submersible pumps (ESPs) are widely used in upstream oil production. The presence of a low concentration solid phase, particle-laden flow, in the production fluid may cause severe damage in the internal sections of the pump which reduces its operating lifetime. To better understand the ESP pump's endurance, two different designs of commonly used mixed flow ESPs were studied numerically to determine the pump's flow behavior at its best efficiency point. Computational fluid dynamics (CFD) analysis was conducted on two stages of one design type of pump's primary flow path employing Eulerian–Granular scheme in ANSYS FLUENT. The key parameters affecting the erosion phenomena within the pump such as turbulence kinetic energy, local sand concentration, and near wall relative sand velocity were identified. The predictive erosion model applicable to pumps was developed by correlating the erosion key parameters with available experimental results. It is concluded that the use of an erosion model on the second design of ESP proves the model's versatility to predict the erosion on different designs of ESPs.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092002-092002-9. doi:10.1115/1.4043249.

The present study compares the thermal performance of various alternative refrigerants with conventional refrigerant operating on a vapor compression cycle with energetic, exergetic, and advanced exergetic approaches. Appropriate alternative refrigerants are selected for the analysis, and R1234yf is recommended as the best suitable refrigerant to replace the existing refrigerants. By splitting the exergy destruction into endogenous and unavoidable, endogenous and avoidable, exogenous and unavoidable, and exogenous and avoidable parts, an advanced exergy method depicts the real potentials for the improvement in the thermal system. Moreover, a traditional exergy method prefers condenser for performance improvement as it has 18.48% higher exergy destruction than evaporator, whereas the advanced exergy method proposes evaporator rather than condenser since its endogenous and avoidable destruction part is 26.38% more than condenser for R1234yf refrigerant.

Commentary by Dr. Valentin Fuster

Research Papers: Fuel Combustion

J. Energy Resour. Technol. 2019;141(9):092201-092201-8. doi:10.1115/1.4043250.

We have developed a surrogate blending methodology to identify surrogates with a desired degree of complexity. Along with estimation methods for various physical and chemical properties for fuel blends, we have assembled and developed a rich library of over 60 fuel components. The components cover a carbon number range from 1 to 20, and chemical classes including linear and branched alkanes, olefins, aromatics with one and two rings, alcohols, esters, and ethers. With these, surrogates can be formulated to represent most gasoline, diesel, gaseous fuels, renewable fuels, and several additives. As part of the library, we have assembled self-consistent and detailed reaction mechanisms for all the components, as well as for emissions including NOx and polycyclic aromatic hydrocarbons and a detailed soot-surface mechanism. An extensive validation suite has been used to improve the kinetics database such that good predictions and agreement to data are achieved for the fuel components and fuel-component blends, within experimental uncertainties. This effectively eliminates the need to tune specific rate parameters when employing the kinetics mechanisms in combustion simulations. For engine simulations, the master mechanisms have been reduced using a combination of available reduction methods while strictly controlling the error tolerances for targeted predictions. This approach has resulted in small mechanisms for efficiently incorporating the validated kinetics into computational fluid dynamics (CFD) applications. The surrogate formulation methodology, the comprehensive fuel library, and mechanism reduction strategies suggested in this work allow the use of CFD to explore design concepts and fuel effects in engines with reliable predictions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092202-092202-7. doi:10.1115/1.4043339.

In order to ensure and improve the performance of the fuel vapor-containment system (FVS) on a hybrid electric vehicle (HEV), the vapor pressure field of the evaporative (EVAP) system in the refueling process was analyzed. Numerical models were established to describe the pressure change in the EVAP system. Based on these numerical models, the influences of refueling speed, filler pipe diameter, vent pipe diameter, and fuel vapor-containment valve (FVV) port diameter on pressure change were discussed. The numerical models and the influences of aforementioned effects were validated by experiments. Simulation and experimental results indicated that the vapor pressure field in the EVAP system is more susceptible to the change of refueling speed and FVV port diameter. If the refueling speed increased and the FVV port diameter decreased, the vapor pressure in the EVAP system strongly fluctuated. Furthermore, results also show that the FVV port diameter should be as large as possible but less than 20 mm, while refueling speed should be 50 l/min. The filler pipe diameter can be chosen in the range of 23–28 mm.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092203-092203-12. doi:10.1115/1.4043325.

Due to perspective of biomass usage as a viable source of energy, this paper suggests a potential theoretical approach for studying multiregion nonadiabatic premixed flames with counterflow design crossing through the mixture of air (oxidizer) and lycopodium particles (biofuel). In this research, convective and radiative heat losses are analytically described. Due to the properties of lycopodium, roles of drying and vaporization are included so that the flame structure is created from preheating, drying, vaporization, reaction, and postflame regions. To follow temperature profile and mass fraction of the biofuel in solid and gaseous phases, dimensionalized and nondimensionalized forms of mass and energy balances are expressed. To ensure the continuity and calculate the positions of drying, vaporization, and flame fronts, interface matching conditions are derived employing matlab and mathematica software. For validation purpose, results for temperature profile is compared with those provided in a previous research study and an appropriate is observed under the same conditions. Finally, changes in flame velocity, flame temperature, solid and gaseous fuel mass fractions, and particle size with position measured from the position of stagnation plane, strain rate, and heat transfer coefficient in the presence/absence of losses are evaluated.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Engineering

J. Energy Resour. Technol. 2019;141(9):092901-092901-9. doi:10.1115/1.4043136.

Carbonate rocks are generally highly heterogeneous that make it difficult to accurately assess the behavior of fluid flow and transport in them. In this paper, we experimentally investigate the oil–water displacement in carbonate reservoirs by mimicking the typical pore vugs of carbonates through fabricating glass micromodels. The micromodels were saturated completely with oil, and then water was injected continuously at a constant rate until a steady state was achieved. After that, the injection rate was increased in steps. For each injection rate, water was continuously injected until a steady state was achieved and then increased to the next injection rate. For each injection rate, the displacement process of oil and water in the micromodel was captured by a digital video camera. Experimental results show that water breakthrough occurs in pure-fracture channels earlier than that in fracture-cavity channels. The wettability and pore networks of fractures and vugs have a significant impact on the distribution of trapped oil. Oil is preferential to be trapped in the oil-wet zone and the zone where deviation from the mainstream line starts. Residual oil saturation shows no noticeable change with relatively low injection rates. However, when the injection rate exceeds a critical value, residual oil saturation decreases with an increase in the injection rate.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092902-092902-8. doi:10.1115/1.4043137.

Cement failure is known as one of the major causes for loss of well control events. Cement design is considered as one of the top technological knowledge gaps in high-pressure high-temperature oil and gas exploration. The primary objective of this paper is to perform a parametric analysis and identify critical parameters affecting the mechanical integrity of the set cement sheath. To achieve the objective, three-dimensional finite element models consisting of concentric casings and annular cement sheath were created. The finite element model was validated by analytical calculations. Performance of cement sheath was assessed by analyzing radial, hoop, and maximum shear stresses at different loading conditions. A parametric study was conducted by individually varying influencing factors such as cement material properties, sheath dimensions, and wellbore pressure loads. Values of all parameters were normalized and represented on the same plot against mechanical stresses. Such response curves can be used to estimate whether cement will structurally fail because of various operational loads or material aging. The plot can also be utilized to rank various factors in terms of influence on cement’s performance. Sensitivity response reveals that wellbore pressure, cement material properties, and annulus pressure are major parameters influencing mechanical stresses in neat class G cement. The order of importance depends on the type of stress. Results indicate interfacial bond failure and radial cracking to be the more likely modes of failure for class G cement. Cement response curves can help design engineers and regulators alike in quickly evaluating short-term or long-term fitness-for-service of cement sheath from the perspective of structural integrity. Industry standards and guidelines can be improved by adding performance curves for standard cement recipes.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092903-092903-11. doi:10.1115/1.4043131.

To investigate the characteristics of oil distribution in porous media systems during a high water cut stage, sandstones with different permeability scales of 53.63 × 10−3 μm2 and 108.11 × 10−3 μm2 were imaged under a resolution of 4.12 μm during a water flooding process using X-ray tomography. Based on the cluster-size distribution of oil segmented from the tomography images and through classification using the shape factor and Euler number, the transformation of the oil distribution pattern in different injection stages was studied for samples with different pore structures. In general, the distribution patterns of an oil cluster continuously change during water injection. Large connected oil clusters break off into smaller segments. The sandstone with a higher permeability (108.11 × 10−3 μm2) shows the larger change in distribution pattern, and the remaining oil is trapped in the pores with a radius of approximately 7–12 μm. Meanwhile, some disconnected clusters merge together and lead to a re-connection during the high water cut period. However, the pore structure becomes compact and complex, the residual nonwetting phase becomes static and is difficult to move; and thus, all distribution patterns coexist during the entire displacement process and mainly distribute in pores with a radius of 8–12 μm. For the pore-scale entrapment characteristics of the oil phase during a high water cut period, different enhance oil recovery (EOR) methods should be considered in sandstones correspondent to each permeability scale.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092904-092904-11. doi:10.1115/1.4043132.

In an unconsolidated sandstone reservoir of a deepwater gas field, due to the reduction of the rock compaction by deepwater, sand production is more likely to occur in the reservoir during production under certain production pressure differences. Therefore, it is important to accurately control the production pressure difference. A theoretical analysis model of sand production was established. On the basis of the model, the critical production pressure difference and the critical flow rate of the sand production were tested through indoor simulated experiments of sand production of three-dimensional full-diameter core. In addition, the critical production pressure difference for the sand production with an open hole completion was verified by means of numerical analysis. The analysis procedures and results are as follows: (1) based on the production test, the gas flow rate and the sand production rate under various production pressure differences were measured. It was found that the critical production pressure difference of core of target block was about 2 MPa, which is lower than the critical sand production pressure difference of core in shallow water or land. (2) A finite element analysis model was established by means of a theoretical analysis on the basis of core mechanics testing, and the analytical model was validated by comparing the experimental model and the theoretical model. A plastic deformation criterion for sand production was proposed. (3) The sand production model of the deepwater reservoir was established based on field parameters. The primary parameters that affect the rock strength were analyzed using the sand production criterion, which was verified by the experimental and numerical simulation results. Analysis results show that the effect of cohesive compared with elastic modulus, Poisson's ratio, and angle of internal friction on sand production is greater. At the same time, it should also pay attention to the influence of the drilling and production process on sand production.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092905-092905-11. doi:10.1115/1.4043244.

In oil and gas industry, production optimization is a viable technique to maximize the recovery or the net present value (NPV). Robust optimization is one type of production optimization techniques where the geological uncertainty of reservoir is considered. When well operating conditions, e.g., well flow rates settings of inflow control valves and bottom-hole pressures, are the optimization variables, ensemble-based optimization (EnOpt) is the most popular ensemble-based algorithm for the robust life-cycle production optimization. Recently, a superior algorithm, stochastic simplex approximate gradient (StoSAG), was proposed. Fonseca and co-workers (2016, A Stochastic Simplex Approximate Gradient (StoSAG) for Optimization Under Uncertainty, Int. J. Numer. Methods Eng., 109(13), pp. 1756–1776) provided a theoretical argument on the superiority of StoSAG over EnOpt. However, it has not drawn significant attention in the reservoir optimization community. The purpose of this study is to provide a refined theoretical discussion on why StoSAG is generally superior to EnOpt and to provide a reasonable example (Brugge field) where StoSAG generates estimates of optimal well operating conditions that give a life-cycle NPV significantly higher than the NPV obtained from EnOpt.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092906-092906-11. doi:10.1115/1.4043245.

Drillstrings that include one or more axial oscillation tools (AOTs) are referred to as axial oscillation-supported drillstrings. Downhole vibrations induced by these tools in the drillstring are the most efficient method for friction reduction and improving axial force transfer in high-angle and extended-reach wells. Functional testing of axial oscillation tools prior to downhole operations and modeling the dynamic response of axial oscillation-supported drillstring systems are required to predict the performance and functionality of AOTs. This study presents a practical approach for functional testing of axial oscillation tools and a new analytical model for predicting the dynamic response of axial oscillation-supported drillstrings operating at surface conditions. The axial oscillation-supported drillstring is modeled as an elastic continuous system subjected to viscous damping, frictional contact, and displacement (support excitation). The functional test is a unique experimental test procedure designed to measure the pressure drop, pressure fluctuations, and axial displacement of an axial oscillation tool while varying the flow rate and the spring rate of the tool. The introduction of the spring rate as a variable in the new model and functional testing is unique to this study and not considered in the existing literature. Axial displacement and acceleration predicted from the new model closely agrees with the results obtained from the functional tests. The accuracy of the model is also validated with the results of two previously published functional tests. The comparisons demonstrate an average deviation of approximately 14.5% between predictions and measurements. The axial displacement and pressure drop of AOT increased with flow rate or oscillation frequency. The amplitude of axial displacement increased with frequency because of increased pressure drop.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):092907-092907-11. doi:10.1115/1.4043247.

Mud pollution seriously restricts the development of tight gas reservoirs. For the Dabei tight gas field in Tarim Basin, lots of wells show a higher skin factor on the pressure buildup test curves after drilling. Little researches on mud damage have been conducted for the fracture gas reservoir. Based on the previous researches, a dynamic filtration experimental method utilizing full diameter cores is established for fracture-porous cores under reservoir temperature. Twelve sets of dynamic filtration tests with full diameter cores (D = 10 cm) on the established device and some cuttings microscopic analysis on environmental-scanning-electron microscope/energy dispersive X-ray detector (ESEM/EDX) have been conducted. The effects of core type, fracture width, pressure difference, and mud type on mud damage are all investigated. The results show that the fractured cores suffer a more serious damage degree and exhibit lower return permeability ratio, compared with the porous cores. And the damage degree of fractured cores is proportional to the fracture width and pressure difference. The solids invasion is the key factor damaging the fractured cores, while the porous is mainly impaired by the filtrate invasion. This paper provides a scientific, in-depth understanding of the behaviors, laws, and characteristics of mud damage in fractured and porous cores.

Commentary by Dr. Valentin Fuster

Research Papers: Petroleum Wells-Drilling/Production/Construction

J. Energy Resour. Technol. 2019;141(9):093101-093101-9. doi:10.1115/1.4043246.

Recently, a new type of jet mill bit (JMB) has been introduced to improve the cutting transport efficiency in horizontal drilling by comminuting cuttings into dust-like particles immediately after the cuttings are generated. To promote the application of JMBs in the field, in this work, JMBs were further improved by including junk slots (JS) all around to allow cuttings to flow through the annulus and thereby prevent sticking from occurring while tripping out. Moreover, numerical and experimental investigations on the feasibility of horizontal drilling with the new type of JMB were carried out. The finite element method was used to analyze the strength of the new type of JMB, and flow field simulation analysis was also performed for JMBs with different sizes of JS. The simulation results indicated that the weakest point of the JMB was located at the bit connection instead of the bit frame, and it was demonstrated that the structural strength of the JMB met the requirements of actual working conditions. The JMB JS had a negative effect on promoting the upward return of cuttings from the bottom of the hole, and the larger the slot sizes were, the more negative the effects. Through a trip-out experiment with the new type of JMB, this paper studied the influence of the slot size on the trip-out process safety. The experimental results indicated that the minimum safe slot width was 60 mm. Finally, in a synthesis of the simulation and experimental results, the reasonable range of slot width was determined to be 60–70 mm; the aforementioned range was the most suitable for the bit based on safety and efficiency considerations. This paper provides guidance for the improvement and application of JMBs.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2019;141(9):093102-093102-7. doi:10.1115/1.4043248.

High-performance drilling fluid was designed for unconventional reservoirs to minimize the formation damage and borehole instability using organophilic clay treated with trimethyloctylammonium bromide, novel in-house synthesized gemini surfactant, and a high-molecular weight polymer. This gemini surfactant has not been reported in the literature for drilling fluid applications. The performance of designed drilling fluid was evaluated and compared with the base drilling fluid (4 w/v.% bentonite dispersion water). Shale dispersion, linear swelling, filtration, and rheological experiments were performed to investigate the effect of drilling fluids on borehole stability and formation damage. The combined use of organophilic clay and surfactant in the drilling fluid formulation reduced the shale dispersion up to 89%. The linear swelling experiment of shale sample shows 10% swelling of the core in the modified drilling fluid while in base fluid 13% swelling of shale was observed. It was found that modified drilling fluid interactions with shale were greatly reduced using a surfactant and associative polymer in the drilling fluid formulation. Rheological properties of drilling fluids were stable, and filtration characteristics showed that the filtrate volume was within the acceptable limit. The designed drilling fluid made a thin and impermeable filter cake that prevents the invasion of drilling fluid into the formation. This study opens a new direction to reduce the formation damage and borehole instability using organophilic clay, surfactant and high-molecular weight additive in water-based drilling fluid.

Topics: Fluids , Drilling , Shales , Water
Commentary by Dr. Valentin Fuster

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