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Fluid injection is a common practice in the oil and gas industry found in many applications such as waterflooding and disposal of produced fluids. Maintaining high injection rates is crucial to guarantee the economic success of these projects; however, there are geomechanical risks and difficulties involved in this process that may threat the viability of fluid injection projects. Near wellbore reduction of permeability due to pore plugging, formation failure, out of zone injection, sand production, and local compaction are challenging the effectiveness of the injection process. Due to these complications, modeling and simulation has been used as an effective tool to assess injectors' performance; however, different problems have yet to be addressed. In this paper, we review some of these challenges and the solutions that have been proposed as a primary step to understand mechanisms affecting well performance. [ABSTRACT FROM AUTHOR]

The article focuses on the peer-reviewed papers that were published from the 40th International Technical Conference on Clean Coal and Fuel Systems held during May 31-June 4, 2015. The selected papers from the conference cover topics that are importance for clean energy conversion using coal and solid fuels as well as other hydrocarbon fuels.

Highlights the International Green Energy Conference on June 12–16, 2005 in Waterloo, Ontario. Event description; Theme; Attendees; Topics discussed.

Downhole casing leaks in oil and gas wells will highly impact the shallow water horizons and this will affect the environment and fresh water resources. Proactive measures and forecasting of this leak will help eliminate the consequences of downhole casing leaks and, in turn, will protect the environment. Additionally, downhole casing leaks may also cause seepage of toxic gases to the fresh water zones and to the surface through the casing annuli. In this paper, we introduced a risk-based methodology to predict the downhole casing leaks in oil and gas wells using advanced casing corrosion logs such as electromagnetic logs. Downhole casing corrosion was observed to assess the remaining well life. Electromagnetic (EM) corrosion logs are the current practice for monitoring the casing corrosion. The corrosion assessment from EM logs is insufficient because these logs cannot read in multiple casings in the well. EM tool gives average reading for the corrosion in the casing at a specific depth and it does not indicate the orientation of the corrosion. EM log does not assess the 360 deg corrosion profile in the casing and it only provides average value and this may lead to wrong decision. All of this makes EM logs uncertain tools to assess the corrosion in the downhole casing. A unified criterion to assess the corrosion in the casing and to decide workover operations or not has been identified to minimize the field challenges related to this issue. A new approach was introduced in this paper to enhance the EM logs to detect the downhole casing corrosion. Corrosion data were collected from different fields (around 500 data points) to build a probabilistic approach to assess the casing failure based on the average metal loss from the EM corrosion log. The failure model was used to set the ranges for the casing failure and the probability of casing failure for different casings. The prediction of probability of failure (PF) will act as proactive maintenance which will help prevent further or future casing leaks. [ABSTRACT FROM AUTHOR]

Biodiesel has emerged as a suitable alternative to mineral diesel in compression ignition (CI) engines in order to ensure global energy security and to reduce engine out emissions in near future. Biodiesel derived from various feedstocks available worldwide fits well in the current fuel supply arrangement for transport sector. However, biodiesel as an alternative transportation fuel has been extensively investigated because of differences in its important fuel properties compared with baseline mineral diesel. Since fuel properties greatly influence spray development, combustion, and emission formation in internal combustion (IC) engines, a number of experimental and computational studies on biodiesel usage in CI engines have been performed to determine its brake thermal efficiency (BTE), gaseous emissions, durability, etc., by various researchers using variety of engines and feedstocks. In the present paper, a critical review of the effect of biodiesel's fuel properties on engine performance, emissions, and combustion characteristics in existing diesel engines vis-a-vis conventional diesel has been undertaken. In addition, the progress and advances of numerical modeling involving biodiesel are also reviewed to determine the effect of fuel properties on spray evolution and development of reaction mechanisms for biodiesel combustion simulations. Fuel properties are discussed in two categories: physical and chemical properties, which are key parameters affecting spray and combustion processes. Subsequent sections review spray, combustion, emissions, and performance characteristics of biodiesels under various engine operation conditions. In the last section of this review paper, numerical modeling of biodiesel covering recent numerical models and schemes to understand the behavior of biodiesel combustion and pollutants formation is included. This review paper comprehensively summarizes biodiesel fuel's (BDFs) spray, combustion, and emission characteristics using experimental and numerical approaches. Limitations and scope for future studies are discussed in each section. [ABSTRACT FROM AUTHOR]

In an earlier publication (Jupudi et al., 2016, "Application of High Performance Computing for Simulating Cycle-to-Cycle Variation in Dual-Fuel Combustion Engines," SAE Paper No. 2016-01-0798), the authors compared numerical predictions of the mean cylinder pressure of diesel and dual-fuel combustion, to that of measured pressure data from a medium-speed, large-bore engine. In these earlier comparisons, measured data from a flush-mounted in-cylinder pressure transducer showed notable and repeatable pressure oscillations which were not evident in the mean cylinder pressure predictions from computational fluid dynamics (CFD). In this paper, the authors present a methodology for predicting and reporting the local cylinder pressure consistent with that of a measurement location. Such predictions for large-bore, medium-speed engine operation demonstrate pressure oscillations in accordance with those measured. The temporal occurrences of notable pressure oscillations were during the start of combustion and around the time of maximum cylinder pressure. With appropriate resolutions in time steps and mesh sizes, the local cell static pressure predicted for the transducer location showed oscillations in both diesel and dual-fuel combustion modes which agreed with those observed in the experimental data. Fast Fourier transform (FFT) analysis on both experimental and calculated pressure traces revealed that the CFD predictions successfully captured both the amplitude and frequency range of the oscillations. Resolving propagating pressure waves with the smaller time steps and grid sizes necessary to achieve these results required a significant increase in computer resources. [ABSTRACT FROM AUTHOR]

The oriented perforating is the essential technique to guide the refracture reorientation, but the influence of the oriented perforation design on the refracture steering radius is still unclear. In this paper, the factors influencing the refracture reorientation were studied by simulation models and experiments. The effects of initial fracture, well production, and perforations on the refracture initiation and propagation were analyzed. Threedimensional finite element models were conducted to quantify the impact of perforation depth, density, and azimuth on the refracture. The large-scale three-axis hydraulic fracturing experiments guided by oriented perforations were also carried out to verify the fracture initiation position and propagation pattern of the simulation results. The research results showed that perforations change the near-wellbore induced stress distribution, thus changing the steering radius of the refracture. According to the simulation results, the oriented perforation design has a significant influence on the perforation guidance effect and refracture characteristics. Five hydraulic fracturing experiments proved the influence of perforating parameters on fracture initiation and morphology, which have a right consistency between the simulation results. This paper presents a numerical simulation method for evaluating the influence of the refracture reorientation characteristics under the consideration of multiple prerefracturing induced-stress and put forward the oriented perforation field design suggestions according to the study results. [ABSTRACT FROM AUTHOR]

Blooey line is a discharge pipe, used to conduct gas to keep drilling rock dust and cuttings away from the drilling rig, reducing the fire hazard and transporting the cuttings to a suitable distance from the well. In this paper, the blooey line's flow capacity and erosion mechanism have been investigated by numerical and experimental method. The model of blooey line, which is commonly used in Sichuan district, China, is established by using a computational fluid dynamics (CFD) method. And, the distribution of pressure field and velocity field in the blooey line are investigated by the CFD model. And, the effect of gas flow rate on impact force and erosion is also discussed. Compared with the simulation results, an experimental apparatus of the blooey line has been conducted under the mechanical similarity principle. The impact force and pressure on the elbows are measured under different gas flow rates. The numerical simulation and experimental method proposed in this paper can provide a reference for layout optimization and flow capacity calculation of blooey line in gas drilling. [ABSTRACT FROM AUTHOR]

This paper presents the approach of thermoeconomic analysis of centralized cold generation in trigeneration system integrated with steam-powered absorption chillers (ACs). The analysis was conducted for real back-pressure combined heat and power (CHP) unit BC-50 and single-effect absorption refrigerators using water and lithium bromide as the working fluids. It has been assumed that the heating medium supplied to the chiller generator is technological steam from the existing steam bleeding. The calculations take into account changes of energy demand for heating and cooling for each month of the year. Mathematical simulation models of cogeneration and trigeneration systems have been developed with the commercial program for power plant simulation EBSILON PROFESSIONAL. System effects of heat and electricity cogeneration and cogeneration with additional cold production have been calculated compared to separate production of heat, electricity, and cold (replaced heating plant and power unit). The effect of trigeneration has been assessed quantitatively by the coefficient of the increasing cogeneration effects, which has been calculated as a ratio of chemical energy savings of fuels to the demand for heat by the consumers in the cases of trigeneration and cogeneration. This paper includes also analysis of economic effectiveness of a trigeneration system with ACs for cold agent production. The results of economic calculations show that an acceptable payback period of approximately 13 yr for a CHP and absorption system may be achieved. Discounted payback (DPB) is equal to the half of assumed operating time of the system. Sensitivity analysis shows that the most important impact on profitability is the selling price of cold and the purchase of fuel--hard coal. [ABSTRACT FROM AUTHOR]

The aim of this paper is to identify and investigate the potential and limitations of diesel-gas combustion concepts for high speed large engines operated in gas mode with very small amounts of pilot fuel (<5% diesel fraction). Experimental tests were carried out on a flexible single cylinder research engine (displacement 6.24 dm³) equipped with a common rail system. Various engine configurations and operating parameters were varied and the effects on the combustion process were analyzed. The results presented in this paper include a comparison of the performance of the investigated dual fuel concept to those of a state-of-the-art monofuel gas engine and a state-of-the-art monofuel diesel engine. Evaluation reveals that certain limiting factors exist that prevent the dual fuel engine from performing as well as the superior gas engine. At the same NOx level of 1.3 g/kWh, the efficiency of the dual fuel engine is ≈3.5% pts. lower than that of the gas engine. This is caused by the weaker ignition performance of the injected pilot fuel compared to that of the gas scavenged prechamber of the gas engine. On the other hand, the dual fuel concept has the potential to compete with the diesel engine. The dual fuel engine can be operated at the efficiency level of the diesel engine yet with significantly lower NOxemissions (3.5 g/kWh and 6.3 g/kWh, respectively). Since the injection of pilot fuel is of major importance for flame initialization, and thus for the main combustion event of the dual fuel engine, optical investigations in a spray box, measurements of injection rates, and three-dimensional (3D) computational fluid dynamics (CFD) simulation were conducted to obtain even more detailed insight into these processes. A study on the influence of the diesel fraction shows that diminishing the diesel fraction from 3% to lower values has a significant impact on engine performance because of the effects of such a reduction on injection, ignition delay, and initial flame formation. The presented results illustrate which operating strategy is beneficial for engine performance in terms of low NOx emissions and high efficiency. Moreover, potential measures can be derived which allow for further optimization of the diesel-gas combustion process. [ABSTRACT FROM AUTHOR]

Drill-bit vibrations and bit wear have been identified as the two major causes for premature polycrystalline diamond-compact (PDC) bit failure and difficulty in accurately predicting PDC bit performance. The objective of this paper is to present a new approach to drilling optimization by developing an algorithm that defines and generates a constrained stable rotary speed (RPM)-weight-on-bit (WOB) working domain for a given system as opposed to the traditional RPM-WOB charts. The algorithm integrates the dynamicstability model for bit vibrations with the bit-performance model for degraded bits. This study addresses the issues of dynamic-bit stability under torsional and lateral vibrations coupled with bit wear. The approach presented in this paper involves performing two separate analyses: vibration stability and bit-wear performance analysis. The optimum operating conditions are estimated at each depth of the drilling interval, taking into consideration the effect of bit wear and bit vibrations. Because the bit wears continuously while penetrating the rocks, discretization of depth is necessary for effective simulation. Discretization is done by dividing the drilling interval into subintervals of the desired length. Vibration-stability analysis and bit-wear performance analysis are preformed separately at every subinterval and then integrated over the discrete interval. For every subinterval, a WOB-RPM domain is determined within which the given system is dynamically stable (for vibrations), and the bit wear does not exceed the maximum allowable wear (MAW) for the section of the drilling interval selected. A unique concept to relate the fractional change in hydromechanical specific energy (HMSE) to the fractional change in bit wear has also been put forward that further constraints the WOB-RPM stable working domain. The new coupled vibration-stability chart, including the maximum rate of penetration (ROP), narrows down the conventional chart and provides different regions of operational stability. It has also been found that as the compressive strength of the rock increases, the bit-gauge friction factor also increases, which results in a compressed or reduced allowable working domain, both from the vibration-stability analysis and bit-performance analysis. Simple guidelines have been provided using the new stability domain chart to estimate the operating range for real-time optimization. [ABSTRACT FROM AUTHOR]

Casing integrity management is crucial, especially in wells experiencing severe casing wall degradation. Knowledge of stress distribution in worn casing helps predict where a casing failure occurs first. In industrial practice, a common method is to estimate the reduction of the casing burst strength in worn casing using API burst strength equation with a linear reduction in the remaining wall thickness or wear percentage equivalent to a "uniform-worn" casing model. This study focuses on building a rigorous engineering model for burst strength degradation prediction based on "crescent shape" casing wear. This model calculates the hoop strength directly, including the local bending in the thinner portion of the "crescent-worn" casing. This paper has developed a mathematical model to calculate the hoop strength of worn out casing with force and moment balance equations. This study finds the calculation of reduced strength using the linear wear model to be overly conservative because it only focuses on the stress at the thinnest portion of the worn casing. The stress predicted in this paper is similar to the results obtained from the finite element method (FEM), which validates equations and results obtained from this paper. The developed model is generic and can apply to casings, risers, and tubings. [ABSTRACT FROM AUTHOR]

Combustion processes of two fuels, pulverized coal and biomass, in furnaces take place at steady state. Combustion of condensed fuels involves one-way interfacial flux due to phenomena in the condensed phase (evaporation or pyrolysis) and reciprocal ones (heterogeneous combustion and gasification). Many of the species injected in the gas phase are later involved in gas phase combustion. This paper presents results of combustion process of two-phase charge contained coal and wetted biomass, where the carrier was the air with given flow rate. The furnace has three inlets with assumed inlet flow rate of coal, biomass, and air, and combustion process takes place in the furnace fluidized space. The simulation of such combustion process was carried out by numerical code of open source computational fluid dynamics (CFD) program CODE_SATURNE. For both fuels, the moist biomass with following mass contents: C=53%, H=5.8%, O=37.62%, ash=3.6, and mean diameter of molecules equal to 0.0008 m and pulverized coal with following mass contents: C=76.65%, H=5.16%, O=9.9%, ash=6.21%, and mean molecule diameter 0.000025m were used. Devolatilization process with kinetic reactions was taken into account. Distribution of the main combustion product in furnace space is presented with disappearance of the molecules of fuels. This paper presents theoretical description of the two-phase charge, specification of the thermodynamic state of the charge in inlet boundaries and furnace space, and thermal parameters of solid fuel molecules obtained from the open source postprocessor PARAVIEW. [ABSTRACT FROM AUTHOR]

Salt-laden hog fuel (wood waste) is burnt in a fluidized bed boiler converted from a traveling grate boiler to generate steam for a specialty paper mill. The converted boiler has a design capacity of 156 t/h of steam from hog and actual generation has varied from 76% to 107% of the design capacity. The conversion has resulted in more stable operation, more complete combustion, less ash production, reduced boiler maintenance, and lower fossil fuel consumption. Tire derived fuel (TDF) is used as a supplementary fuel. With an energy content of 31 Gilt for TDF, as compared to 8 GJ/t for wet hog, addition of 2%-5% TDF by weight increased the bed temperature by an average of 55°C, stabilized and improved the combustion of low quality hog and high moisture content sludge. The impact of TDF addition was studied in detail. Stack emissions were tested and bottom and flyash samples were analyzed. Although TDF contains an average of 1.6% zinc and 9.2% steel wire by weight, addition of TDF did not affect total particulate emissions from the boiler SO2 emissions were increased due to the high sulfur content of TDF (1.4%), while NOx emissions were reduced. A good correlation was obtained from the test results, showing that the addition of TDF resulted in a reduction in both the total formation and the stack emissions of dioxins and furans. [ABSTRACT FROM AUTHOR]

Since it is important to prevent the wake produced by upstream wind turbines from interfering with downstream wind turbines, a method of deflecting such wakes is desired. In this paper, we present the coupled analysis results of a computational fluid dynamics (CFD) simulation involving a three-bladed rigid wind turbine with a yaw control system that utilizes rFlow3D CFD code, which was developed by the Japan Aerospace Exploration Agency (JAXA), primarily for rotorcraft use. Herein, a three-dimensional (3D), compressible, and unsteady Reynolds-averaged Navier-Stokes (RANS) equation with a Spalart-Allmaras turbulence model is adopted as the governing equation. In this study, wind turbine computations using various wind turbine yaw angles are performed while focusing on the resulting wake velocity distribution and aerodynamic loads, after which the influences of the yaw angle are discussed. Next, based on the wake velocity distribution results for each yaw angle, we move on to a wake interference avoidance simulation for downstream wind turbines that utilizes two prepared wind turbines. Through this study, the following characteristics were confirmed. The results show wake deflection produced by adding yaw angle can provide a sufficient wake skew angle even in far-wake events. Furthermore, the yaw angle introduction accelerates the progression of vortex dissipation and brings about early velocity recovery in the wake region. Simultaneously, the introduction decreases the power generation amount of the yawed upstream wind turbine and increases the fatigue load of flapwise moment added to the blade root. In this paper, the details of flow field, oscillation, and the yawed wind turbine performance characteristics will also be described. [ABSTRACT FROM AUTHOR]

Production forecast of steam-assisted gravity drainage (SAGD) in heterogeneous reservoir is important for reservoir management and optimization of development strategies for oil sand operations. In this work, artificial intelligence (AI) approaches are employed as a complementary tool for production forecast and pattern recognition of highly nonlinear relationships between system variables. Field data from more than 2000 wells are extracted from various publicly available sources. It consists of petrophysical log measurements, production and injection profiles. Analysis of a raw dataset of this magnitude for SAGD reservoirs has not been published in the literature, although a previous study presented a much smaller dataset. This paper attempts to discuss and address a number of the challenges encountered. After a detailed exploratory data analysis, a refined dataset encompassing ten different SAGD operating fields with 153 complete well pairs is assembled for prediction model construction. Artificial neural network (ANN) is employed to facilitate the production performance analysis by calibrating the reservoir heterogeneities and operating constraints with production performance. The impact of extrapolation of the petrophysical parameters from the nearby vertical well is assessed. As a result, an additional input attribute is introduced to capture the uncertainty in extrapolation, while a new output attribute is incorporated as a quantitative measure of the process efficiency. Data-mining algorithms including principal components analysis (PCA) and cluster analysis are applied to improve prediction quality and model robustness by removing data correlation and by identifying internal structures among the dataset, which are novel extensions to the previous SAGD analysis study. Finally, statistical analysis is conducted to study the uncertainties in the final ANN predictions. The modeling results are demonstrated to be both reliable and acceptable. This paper demonstrates the combination of AI-based approaches and data-mining analysis can facilitate practical field data analysis, which is often prone to uncertainties, errors, biases, and noises, with high reliability and feasibility. Considering that many important system variables are typically unavailable in the public domain and, hence, are missing in the dataset, this work illustrates how practical AI approaches can be tailored to construct models capable of predicting SAGD recovery performance from only log-derived and operational variables. It also demonstrates the potential of AI models in assisting conventional SAGD analysis. [ABSTRACT FROM AUTHOR]

The application of equilibrium thermodynamics in the study of thermal plant performance under real operating conditions is a constant challenge. In this paper, an analysis of a reservoir pressure piston working between two linear flow resistances is performed by considering the friction of the piston cylinder system on the walls. The proposed model is developed to obtain the optimum power output and speed of the piston in terms of first law efficiency. If the friction on the piston-cylinder assembly is neglected, the expressions obtained are consistent with those presented in the literature under laminar regime. It was also demonstrated that for both laminar and turbulent regimes with overall size constraints, the power delivered can be maximized by balancing the upstream and downstream flow resistances of the piston. This paper also evaluated the influence of the overall size constraints and flow regime on the performance of the piston cylinder. This analysis is equivalent to evaluate the irreversibilities in an endo-irreversible Carnot heat engine with heat loss resistance between the engine and its heat reservoirs. The proposed model introduced some modifications to the results obtained from the recent literature and led to important conclusions. Finally, the proposed model was applied to calculate the lost available work in a turbine operating at steady flow conditions with an ideal gas as working fluid. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this paper, a new approach for model-based monitoring of turbine heat rate is developed, where the superheat steam flow is calculated according to the output power of the turbine generation instead of the flow of feed water. A regenerative system model is built based on the operating state and historical data to predict the parameter values in the heat rate calculation. The results of the model calculation also verify the turbine operating parameters that are measured on site. The new approach in this paper was applied in a 660 MW generation unit. The monitoring results of this approach are more stable and accurate than traditional monitoring results. [ABSTRACT FROM AUTHOR]

Distributed energy systems are gaining widespread popularity in recent times as they are capable of generating power with a minimum running cost. They are also highly effective since they are located close to the load which reduces the transmission losses to a significant extent. Energy starved countries have opened up business opportunities to industries which can generate electricity and export them to the grid. The purpose of this paper is to evaluate the economic feasibility of using a compressed air energy storage (CAES) system for distributed generation sources or captive power plants when it operates in islanded mode. This paper presents the application of CAES system as a viable energy storage method to be used as a dump load when the source operates in islanded mode. Based on the data of a sample case, cost analysis is being carried out to ensure the economic feasibility of implementing such a system for a captive power plant. The detailed cost analysis for implementing such a system is presented together with a simple methodology to be followed for selecting a compressor. Implementing an energy storage system always improves the performance of the system as it is capable of smoothing out the fluctuations. For plants which are exporting power to the grid, it also improves the operating profit of the plant by acting as a buffer in situations when there are minor disturbances in the grid and the plant is forced to operate in islanded mode. The sample case study is being done for the possible application and implementation of the suggested energy storage system, and the findings show that even though the initial cost of such a system is on the higher side, it can be helpful in the long run. The proposed system will be helpful to supply peak loads and also increases the profit of such sources who export power to the grid. The proposed system is applicable only to sources which are connected to the grid and it works well only when there is a sustained period of operation in islanded mode. [ABSTRACT FROM AUTHOR]

The aim of this work is to study a binary Rankine process with a significantly higher efficiency compared to a conventional coal-fired power plant. This paper focuses on the design of the process and especially on an efficient combination of flue gas, potassium, and water streams in the components of the steam generator, such as economizers, evaporators, and superheaters, to decrease the overall exergy destruction. Based on a literature review, a base case for a coal-fired binary Rankine cycle with potassium and water as working fluids was developed and, in order to evaluate the thermodynamic quality of several variants, comparative exergy analyses were conducted. A simulation of the process and calculation of the values for the streams were carried out by using the flow-sheeting program CycleTempo, which simultaneously solves the mass and energy balances and contains property functions for the specific enthalpy and entropy of all the substances used. Necessary assumptions are predominantly based on literature data or they are discussed in the paper. We present the exergy analysis of the overall process that includes the flue gas streams as well as the potassium and water cycles. A design analysis and sensitivity studies show the effects of stream combinations and key parameters on the net efficiency, which is higher than 50%. [ABSTRACT FROM AUTHOR]

The direct heat exchange network (direct flow mixing network) and the indirect heat exchange network (exchanger network) are two of the elements that constitute a water network where heat and mass are transferred. When designing these systems, it is important to consider different aspects such as thermodynamics and equipment costs. This paper analyzes different design options within the framework of heuristic methodologies on a case study taken from the open literature. Two design methodologies are compared on the basis of exergy losses. It also enunciates a series of considerations in heuristic design for the heat and mass exchange networks. A very helpful tool in relation with the considerations set out herein is the composite curve; special focus will be given during its construction. This paper shows how to incorporate the exergy component in design seeking to minimize the thermal irreversibility. [ABSTRACT FROM AUTHOR]

The large-scale production of renewable energy is limited by the intermittence nature of the renewable energy sources. Moreover, the electricity production of the thermal and nuclear power plants is not flexible with the electricity demand. Hence, the integration of energy storage technologies into the grid has become crucial as it creates a balance between supply and demand for electricity and protects thereby the electrical grid. Among the large-scale energy storage technologies, a novel adiabatic compressed air energy storage (A-CAES) system will be developed in this paper. This storage system is characterized, compared to the conventional compressed air energy storage (CAES) system, by the recovery and the reuse of the compression heat in order to improve the system efficiency and avoid the use of fossil fuel sources. This paper discusses a comparison between the static and dynamic modeling of the A-CAES system performed by a computer simulation using "Modelica." Unlike the static model, the dynamic model takes into account the mechanical inertia of the turbomachinery (compressors and turbines) as well as the thermal inertia of the heat exchangers. Consequently, it enables studying the flexibility of the storage system and its ability to meet the electrical grid requirements (primary and secondary reserves) by evaluating the duration of the transient states. Furthermore, the comparison between the static and dynamic models permits to estimate the efficiency losses due to the transient evolutions.The results show that the storage system needs more than 2 min before being able to consume all the excess energy available on the electrical grid and more than 5 min before being able to produce all the energy required by the electrical grid. These time frames are due especially to the transient states (start-up) of the turbomachines. Finally, the system efficiency is 64.7%, the transient states of the system cause losses of 0.9%. These small losses are explained by the short duration of the transient states relative to that of the steady states (15 hrs). [ABSTRACT FROM AUTHOR]

Materials such as added clays, weight materials, drill solids, and metallic wear products in the drilling fluid are known to distort the geomagnetic field at the location of the measurement while drilling (MWD) tool magnetometers that are used to measure the direction of well path. This distortion contributes to substantial errors in determination of azimuth while drilling deviated wells. These errors may result in missing the target of a long deviated 12 1/4 in. section in the range of 1-200 m, representing a significant cost to be mitigated. The error becomes even more pronounced if drilling occurs in arctic regions close to the magnetic north pole (or south pole). The effect on the magnetometer readings is obviously linked to the kinds and amounts of magnetic materials in the drilling fluid. The problem has recently been studied by laboratory experiments and analyses of downhole survey data. A series of experiments has been carried out to understand how some drilling fluid additives relate to the magnetic distortion. Experiments with free iron ions show that presence of iron ions does not contribute to magnetic distortion, while experiments with bentonite-based fluids show a strong effect of bentonite on magnetic shielding. Albeit earlier measurements showing a strong dependency of the content of organophilic clay, clean laboratoiy prepared oil-based drilling fluids show no increased shielding when adding organophilic hectorite clays. The anticipated difference between these two cases is outlined in the paper. When eroded steel from an offshore drilling site is added into the oil-based drilling fluid, it is found that these swaif and steel fines significantly increase the magnetic shielding of the drilling fluid. The paper outlines how the drilling direction may be distorted by the presence of these additives and contaminants and how this relates to the rheological properties of the drilling fluid. [ABSTRACT FROM AUTHOR]

Recently developed laboratory and numerical techniques reveal that the very thin, nearwall (assumed) "laminar" fluid layer, an essential feature of all turbulent flow conditions, houses a world of identifiable jetlike structures including bursts generated from the near-wall regions and lumps of fluids projected back onto the wall zones. This activity, identified as "coherent structures" (CS), is recognized as an important mechanism for radial mass transport and energy dissipation, particularly in near-wall or fluid-bed zones. Buoyancy-, adhesion-, hydrodynamic-, and CS-related updraft forces act on particles positioned in the fluid-bed interface zone. Depending on the particle nature, bulk fluid properties, and transport velocity, three pairs of forces were identified corresponding to the equilibrium condition of deposit particles in each of the three size ranges with respect to the onset of entrainment into the bulk flow. This mechanistic approach using a set of force equilibrium equations to assess the potential entrainment of particles was first suggested in 1980 by Phillips and was later (2006) applied by Toma and a research team from ARC and PETRONAS to explain the aging of wall-deposit layer occurring during waxy crude transportation as an effect of size-selective removal of paraffin crystals formed from a mixture of crystalized alkanes. The merit of this paper, regarded as an extension of the 2006 publication, is to introduce a more general selective extraction rate function that enables calculations of both the rate of paraffin aging and size alteration of any fine, polydisperse particulate matter exposed to bulk turbulent flow, gas or liquid. Without any adjustment of the process or physical constants, the modeling results presented in this paper compared satisfactorily with the experimental results obtained independently by the Texaco Research (aging of waxy crude) and laboratoiy data from the University of Alberta on the effect of size-selective extraction of fine sand or glass beads (GB) initially deposited on the bottom of a pipe and exposed to a turbulent bulk flow of water. An overarching objective of this paper is to stir interest in mechanistic modeling and prediction of size-selective radial transport and separation for a broad range of industrial and environmental applications and studies and specifically in the recognition and use of burst-sweep CS structures for calculating radial transport of small particle sizes, particularly in near-interface zones exposed to turbulent flow conditions. [ABSTRACT FROM AUTHOR]

Gasoline compression ignition (GCI), also known as partially premixed compression ignition (PPCI) and gasoline direct injection compression ignition (GDICI), engines have been considered an attractive alternative to traditional spark ignition (SI) engines. Lean-burn combustion with the direct injection of fuel eliminates throttle losses for higher thermodynamic efficiencies, and the precise control of the mixture compositions allows better emission performance such as NOx and particulate matter (PM). Recently, low octane gasoline fuel has been identified as a viable option for the GCI engine applications due to its longer ignition delay characteristics compared to diesel and lighter evaporation compared to gasoline fuel (Chang et al„ 2012, "Enabling High Efficiency Direct Injection Engine With Naphtha Fuel Through Partially Premixed Charge Compression Ignition Combustion," SAE Technical Paper No. 2012-01-0677). The feasibility of such a concept has been demonstrated by experimental investigations at Saudi Aramco (Chang et al„ 2012, "Enabling High Efficiency Direct Injection Engine With Naphtha Fuel Through Partially Premixed Charge Compression Ignition Combustion," SAE Technical P aper No. 2012-01-0677; Chang et al., 2013, "Fuel Economy Potential of Partially Premixed Compression Ignition (PPCI) Combustion With Naphtha Fuel," SAE Technical Paper No. 2013-01-2701). The present study aims to develop predictive capabilities follow octane gasoline fuel compression ignition (Cl) engines with accurate characterization of the spray dynamics and combustion processes. Full three-dimensional simulations were conducted using CONVERGE as a basic modeling framework, using Reynoldsaveraged Navier-Stokes (RANS) turbulent mixing models. An outwardly opening hollow-cone spray injector was characterized and validated against existing and new experimental data. An emphasis was made on the spray penetration characteristics. Various spray breakup and collision models have been tested and compared with the experimental data. An optimum combination has been identified and applied in the combusting GCI simulations. Linear instability sheet atomization (LISA) breakup model and modified Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) break models proved to work the best for the investigated injector. Comparisons between various existing spray models and a parametric study have been carried out to study the effects of various spray parameters. The fuel effects have been tested by using three different primary reference fuel (PRF) and toluene primary reference fuel (TPRF) surrogates. The effects of fuel temperature and chemical kinetic mechanisms have also been studied. The heating and evaporative characteristics of the low octane gasoline fuel and its PRF and TPRF surrogates were examined. [ABSTRACT FROM AUTHOR]

Approximately, 55% of the energy produced from conventional vehicle resources is lost due to heat losses. An efficient waste heat recovery process will lead to improved fuel efficiency and greenhouse gas emissions. Thermoelectric generators (TEGs) are heat recovery devices that are being widely studied by a range of energy-intensive industries. Efficient solid-state thermoelectric devices are good candidates to reduce fuel consumption in an automobile. Thermoelectric materials have had limited automotive applications due to the automotive waste heat recovery temperature range, the rarity and toxicity of some materials, and the limited ability to mass manufacture thermoelectric devices from expensive TE materials. However, skutterudite is one class of material that has demonstrated significant promise in the transportation waste heat recovery temperature domain. Durability and reliability of the TEGs are the most significant concerns in the product development process. Cracking of the materials at hot-side interface is found to be a major failure mechanism of TEGs under thermal loading. Cracking affects not only the structural integrity but also the energy conversion and overall petformance of the system. In this paper, cracking of thermoelectric material as observed in performance testing is analyzed using numerical simulations and analytic experiments. This paper shows, with the help of finite element analysis (FEA), the detailed distribution of stress, strain, and temperature is obtained for each design. Finite element (FE)-hased simulations show the tensile stresses as the primary factor causing radial and circumferen tial cracks in the skutterudite. For a TEG design, loading conditions and closed-form analytical solutions of stress!strain distributions are derived. Scenarios with minimum tensile stresses are sought. These approaches yield the minimum of stress/strain fields which produce cracks. Finally, based on these analyses and computational fluid dynamics (CFD) studies, strategies in tensile stress reduction and failure prevention are proposed. [ABSTRACT FROM AUTHOR]

The energy sector in the European market has been changing significantly over the last years. European Union (EU) energy strategy includes the EU low-carbon roadmap milestone, which indicates for 2020, a 20% reduction in carbon emissions, and a 20% EUwide share for renewables, and by 2030 a 40% reduction in carbon emissions and 30% EU-wide share for renewables. The increased renewable energy sources (RES) penetration and their intermittent energy production have led to the emerging need for energy storage technologies. Especially in the European energy market, large-scale energy balancing with sustainable technologies with product flexibility and cost-effective operation are being investigated. The carbon capture and utilization (CCU) concept, as a means for low-carbon sustainable industries, is integrated in the energy storage technologies. The present paper addresses the integration of power to fuel concept in the energy storage sector with simultaneous emission reduction. Grid management, the scale, and the efficient operation of electrolyzers are the basis for the implementation of Power to Fuel technology. The use of surplus and/or low-cost electricity via water electrolysis to commute captured CO2 from industrial plants to versatile energy carriers such as methane and methanol is being investigated in the present paper. Shadow operation of fossil fuel power plants under minimum load conditions leads to optimized energy dispatch of the power plants and provides product flexibility in terms of electricity, grid services, and chemical production. The produced fuels can be used in highly efficient and wellestablished power systems and further used in the transportation sector or for covering heat demands. The energy efficiency of the different processes is presented and a comparison is made in terms of cost effective energy storage solutions via the simultaneous grid management optimization, the reduction of carbon dioxide, and the production of valuable chemicals. The cross-sectorial concept of the Power to Fuel is presented for Steel and Power industry for the case of methane and methanol production. A review of the U.S. and European markets is made for the application of Power to Fuel. [ABSTRACT FROM AUTHOR]

Wellbore stability has plagued oil industry for decades. Inclusion of the mud in drilling and the effect of mud cake build up incorporate very complex chemical, thermal, mechanical, and physical phenomena. It is very difficult to quantify all these phenomena in one model. The after effects of mud cake buildup, its permeability and variation in thickness with time alter the actual stress profile of the formation. To see the impact of the whole mechanism, a combination of laboratoiy studies and numerical modeling is needed. This paper includes the procedure and results on stress profiles in near wellbore region based on laboratoiy studies of mud cake buildup in high pressure and high temperature environment using permeability plug apparatus (PPA). The damaged formation zone is very susceptible to drilling fluid and results in alteration of existing pore pressure and fracture pressure. This paper presents integrated experimental and analytical solutions for wellbore strengthening due to mud cake plastering. Conducting experiments on rock core disks has provided more realistic results which can resemble tofield conditions. The experimental work here provides an insight to effect of mud cake build up at high pressure and high temperature conditions using a heterogeneous filtration medium prepared from different sandstone cores. Results were used in the analytical model to see the effect of stresses in the formation. The primary objective is to investigate the wellbore hoop stress changes due toformation of filler cake by mud plastering using the analytical models built upon the laboratoiy results. The models developed in this work provide insights to quantify on wellbore plastering effects by mud cake build up. [ABSTRACT FROM AUTHOR]

Low operating cost, comfort, sustainability, and environmental footprint are the key elements of robust space heating (SH) system. In quest for higher efficiencies, it is not always possible to meet all of these demands where environmental footprint often gets secondary attention. This paper presents a novel SH system which is capable of meeting all of the aforementioned elements while simultaneously proving SH and domestic hot water (DHW). The system comprises a geothermal sourced heat pump (HP) featuring "hot gas water" (HGW) technology which delivers higher efficiency. This paper gives a thorough thermodynamic assessment of the system covering component based first and second law analysis and provides test results based on two case studies at a house (W10IW35) and a renovated building (W10/W45). The results show that a theoretical efficiency gain by 11.02% is achievable where the source temperature is 10 °C and the water temperature for floor heating is 35 °C. For the same system, with the same source temperature but with a supply temperature of 45 °C for SH, an efficiency gain of 17.91% is achievable. From experimental testing of the system using the test stand at GeoTherma, 4.73% efficiency gain with water temperature of 35°C and 3.59% efficiency gain with water temperature of 45 °C were obtained. Economic analysis results showed that savings of up to 10% on an annual basis is possible with HGW technology installed in an average family house, whereas it gets 4.36% for a small hotel with a payback time period of about 9 yrs. [ABSTRACT FROM AUTHOR]

In the oil and gas drilling engineering, measurement-while-drilling (MWD) system is usually used to provide real-time monitoring of the position and orientation of the bottom hole. Particularly in the rotary steerable drilling technology and application, it is a challenge to measure the spatial attitude of the bottom drillstring accurately in real time while the drillstring is rotating. A set of "strap-down" measurement system was developed in this paper. The triaxial accelerometer and triaxial fluxgate were installed near the bit, and real-time inclination and azimuth can be measured while the drillstring is rotating. Furthermore, the mathematical model of the continuous measurement was established during drilling. The real-time signals of the accelerometer and the fluxgate sensors are processed and analyzed in a time window, and the movement patterns of the drilling bit will be observed, such as stationary, uniform rotation, and stick-slip. Different signal processing methods will be used for different movement patterns. Additionally, a scientific approach was put forward to improve the solver accuracy benefit from the use of stick-slip vibration phenomenon. We also developed the Kalman filter (KF) to improve the solver accuracy. The actual measurement data through drilling process verify that the algorithm proposed in this paper is reliable and effective and the dynamic measurement errors of inclination and azimuth are effectively reduced. [ABSTRACT FROM AUTHOR]

Palm methyl ester (PME) is an attractive alternate biofuel produced by the transesterification of palm oil with methanol. This paper is a sequel to our earlier papers on the comparison of the flame structure and emission characteristics of neat PME with those of petroleum-derived fuels (No. 2 diesel and neat Jet A). Blends of prevaporized Jet A fuel and PME (25%, 50%, and 75% by volume) were studied in a laminar flame environment at burner-exit equivalence ratios of 2, 3, and 7. The global combustion characteristics including flame length, CO and NO emission indices, radiative heat fraction, and in-flame profiles of species concentration (CO, CO2, NO, and O2), temperature, and soot volume concentration were measured. The global CO emission index decreased significantly with the PME content in the blend at an equivalence ratio of 7; a 30% reduction was observed with the addition of 25% PME by volume, and a further reduction of 25% was observed with the addition o f another 25% PME. The global NO emission index of the neat PME flame was 35% lower than that of the Jet A flame at an equivalence ratio of 2. The near-burner homogeneous gas-phase reaction zone increased in length with the addition of PME at all equivalence ratios. The concentration measurements highlighted the nonmonotonic variation o f properties with the volume concentration of PME in the fuel blend. The fuel-bound oxygen and hydrogen of PME affected the combustion properties significantly. [ABSTRACT FROM AUTHOR]

Creating complex fracture network by hydraulic fracturing operation in unconventional reservoir development is the key factor of effective exploitation. The mechanism of creating a fracture network is not clear up to today. Conventional hydraulic fracturing theory is based on tensile failure of a rock, and a hydraulic fracture is widely accepted as propagating along the direction of in situ maximum horizontal principal stress in the industry. Based on rock elastic mechanics and fracture mechanics, considering combined tensile and shear failures, the maximum circumferential strain criterion and boundary element method (BEM), the paper studies the induced stress and its variation during a fracture propagation, the interaction between two or more hydraulic fractures, and the interaction between a hydraulic fracture and a natural crack. The paper shows that a propagating fracture will produce induced stresses on surrounding rock and form a stress shadow. Instead of propagation along the direction of maximum horizontal principal stress as a single fracture, the outside two fractures of two or more hydraulic fractures are exclusive and turning away from each other. A natural crack may be awaked and extend at its both tips by a propagating hydraulic fracture before their intersection, and the hydraulic fracture may deflect toward the natural crack. The interaction between a hydraulic fracture and a natural crack depends on the transverse distance between them and the initial length of the crack. The shorter the transverse distance and the longer the crack length are, the higher the possibility of the crack to be awaked is. The research results are helpful in understanding complex fracture network and may be used in determining hydraulic fracture places to create a complex fracture network. [ABSTRACT FROM AUTHOR]

The increasing complexities of wellbore geometry imply an increasing well cost. It has become more important than ever to achieve an increased rate of penetration (ROP) and, thus, reduced cost per foot. To achieve maximum ROP, an optimization of drilling parameters is required as the well is drilled. While there are different optimization techniques, there is no acceptable universal mathematical model that achieves maximum ROP accurately. Usually, conventional mathematical optimization techniques fail to accurately predict optimal parameters owing to the complex nature of downhole conditions. To account for these uncertainties, evolutionary-based algorithms can be used instead of mathematical optimizations. To arrive at the optimum drilling parameters efficiently and quickly, the metaheuristic evolutionary algorithm, called the "shuffled frog leaping algorithm, (SFLA) is used in this paper. It is a type of rising swarm-intelligence optimizer that can optimize additional objectives, such as minimizing hydromechanical specific energy. In this paper, realtime gamma ray data are used to compute values of rock strength and bit-tooth wear. Variables used are weight on bit (WOB), bit rotation (N), and flow rate (Q). Each variable represents a frog. The value of each frog is derived based on the ROP models used individually or simultaneously through iteration. This optimizer lets each frog (WOB, N, and Q) jump to the best value (ROP) automatically, thus arriving at the near optimal solution. The method is also efficient in computing optimum drilling parameters for different formations in real time. The paper presents field examples to predict and estimate the parameters and compares them to the actual real-time data. [ABSTRACT FROM AUTHOR]

A conference paper about the use of thermodynamics in explaining useful work or entropy and its application to fuel needs and fuel utilization. Topics discussed include the laws of thermodynamics based on the work produced from hydraulic engines, the relationship between useful work and fuel usage and the difference of available useful work from Gibbs free energy and enthalpy. A mathematical computation of the available useful work from oxidation of methylene (CH2) is described.

Over the last few years, different types of bits have been introduced to meet the challenges of steerable as well as rotary steerable systems; and it is imperative that bits be utilized optimally in these systems. Aw challenges increase with increasing depths, it becomes even more important for one to efficiently utilize the available energy (Robello, S., 2013, "Modeling and Analysis of Drillstring Vibration in Riserless Environment," ASME J. Energy Res. Technol., 135(1), p. 013101). A new correlation identifying inefficient drilling conditions is presented in this paper. Mechanical specific energy (MSE) has been used to improve drilling rates, with mixed results. Hydro MSE (HMSE), which is introduced here, encompasses hydraulic as well as mechanical energy. HMSE quantifies the amount of energy required to drill a unit volume of rock and remove it from underneath the bit. HMSE includes axial, torsional, and hydraulic energy and is different from MSE because it includes a hydraulic term. The initial MSE correlation (Teale, R., 1965, "The Concept of Specific Energy in Rock Drilling," Int. J. Rock Mech. Min. Sci., 2, pp. 57-73.) was modified to accommodate the new hydraulic term. This paper attempts to better model downhole drilling by introducing the hydraulic energy term in the MSE correlation by defining it as HMSE. While the majority of the drilling occurs because of the bit, it is a well-known fact that some drilling occurs due to the "jet impact impingement" caused by the drilling fluid as well. Experimental and field data presented in this paper show that HMSE can identify inefficient drilling conditions. The new hydraulic term included in the specific energy correlation is the key to correctly match the amount of energy required to drill and overcome the strength and stresses of formation being drilled. Also, this new term illustrates how much hydraulic energy is needed to drill faster when the mechanical energy (axial and torsional) is increased. The results also show the importance of including the bit hydraulic energy term into any specific energy analysis for drilling optimization. Field results reveal specific patterns for inefficient drilling conditions and also reveal a good correlation between calculated HMSE and the expected requirements for rock removal under existent conditions of stress at the bit face (Mohan, K., and Robello Samuel, F. A., 2009, "Tracking Drilling Efficiency Using Hydro-Mechanical Specific Energy," SPEIIADC Drilling Conference and Exhibition, March 17-19, Amsterdam, The Netherlands, No. SPE 119421). [ABSTRACT FROM AUTHOR]

Numerous multizone multistage hydraulic fracturing treatments are now being executed in low permeability oil and gas fields around the world. Due to the limited access to the subsurface, post-treatment assessments are mainly limited to few techniques such as tiltmeter, microseismic, and tracer-logs. The first two techniques are mainly used to determine fracture extension; however, fracture height and fracture initiation at all perforation clusters could only be confirmed through radioactive tracer logs or detailed pressure analysis. In this paper, we consider real examples from a field from Central America and investigate potential problems that led to the limited generation of fractures in multizone treatments. For instance, some of the postfrac radioactive logs show very low concentration of tracers at some perforated zones in comparison with other zones. On the other hand in some cases, tracer logs indicate the presence of tracers in deeper or shallower zones. Different reasons could cause fracture growth in nonperforated zones, including but not limited to: perforation design problems, casing/cement integrity problems, lack of containment, instability of fracture growth in one or some of the zones, and finally making a mistake in selecting lithology for fracturing. In this paper, some of these issues have been examined for a few sample wells using treatment pressure data, petrophysical logs, and postfrac tracer logs. Some recommendations in designing the length and arrangement of perforations to avoid these problems in future fracturing jobs are provided at the end of this paper. [ABSTRACT FROM AUTHOR]

An experimental scale desalination pond which utilizes solar energy as a heat source is studied in this paper. The marked solar desalination pond is considered as one of the main stages in a proposed zero discharge desalination process. The effluent waste water of the desalination unit of the petrochemical complex is treated in the proposed zero discharge desalination process to produce potable water and salt. Evaporation distillation method is used in the studied solar desalination pond. Basically, this solar desalination pond is working as batch stage. At the first, the solar-powered desalination pond is introduced then the used method for distillation is discussed and the experimental results are represented in this paper, finally. The results show the feasibility of using the proposed solar-powered pond. The rate of gained distilled water by the proposed solar powered pond is compared with conventional solar pond, finally. [ABSTRACT FROM AUTHOR]

Natural gas and oil exploration and production from shale formations have gained a great momentum in many regions in the past five years. Producing hydrocarbons from shale is challenging because of low productivity of wells. Optimal design of transverse fractures is a key to achieving successful well completion and field economics. This paper presents a simple analytical method to determine the minimum fracture spacing required for preventing fracture-merging. Result of the analytical method has been verified by a Finite Element Method for a typical fracturing condition in a shale gas formation. Field performances of shale gas wells are found consistent with what suggested by this work. The analytical method presented in this paper can replace the sophisticated solutions and time-consuming numerical simulators in calculating stresses around hydraulic fractures and identifying the minimum required fracture spacing. The method can be applied to designing of multifrac completions in shale plays to optimize placement of transverse fractures for maximizing well productivity and hydrocarbon recovery. This work provides engineers a simple tool for optimizing their well completion design in shale gas reservoirs. [ABSTRACT FROM AUTHOR]

Interest is growing in the benefits of homogeneous charge compression ignition engines. In this paper, we investigate a novel approach to the development of a homogenous charge-like environment through the use of porous media. The primary purpose of the media is to enhance the spread as well as the evaporation process of the high pressure fuel spray to achieve charge homogenization. In this paper, we show through high speed visualizations of both cold and hot spray events, how porous media interactions can give rise to greater fuel air mixing and what role system pressure and temperature plays in further enhancing this process. [ABSTRACT FROM AUTHOR]

Microhole coiled tubing drilling is a new technology that provides many added advantages but at the same time poses numerous operational challenges. This manifests itself in a number of ways, all of which adversely affect the efficiency of the drilling process. These problems include increased wellbore friction, poor hole-cleaning, tubular failures, and associated problems during tripping operations. Presently conventional torque and drag models are used to calculate drag forces and surface loads during microhole coiled tubing drilling. However, these estimates might be under conservative. Therefore, an improved model and more comprehensive analysis are required. Conditions expected during microhole coiled tubing drilling are completely different from those encountered during conventional drilling. Further complexity is added when the wellbore is undulated. This paper describes a new analytical model for estimating drag forces by assuming that pipe in the horizontal portion follows a sine function wave due to residual bends and snubbing force. In addition, the model takes into account when the wellbore is also tortuous. Fluid viscosity (an important force in the microhole) is also included so we can calculate appropriate surface loads in addition to drag. This study concludes that besides wellbore inclination, curvature, and wellbore torsion, parameters such as wavelength and contact area also influence the results. This paper documents the comparison between the predicted mathematical simulation results with actual data from wells describing the accuracy and applicability of the model. The analysis results and comparison are presented along with three examples (Zhang et al., 2013, "Analytical Model to Estimate the Drag Forces for Microhole Coiled Tubing Drilling," Society of Petroleum Engineers, Paper No. SPE 163480.). [ABSTRACT FROM AUTHOR]

In high-risk, high-cost environments, such as ultra-deep waters, refining advanced technologies for the successful completion of wells is paramount. Challenges are still very much associated with complex bottomhole assemblies (BHAs) and with the vibration of the drillstring when used with hole enlarging tools. These tools with complex profiles and designs become additional excitation sources of vibration. The more widespread use of downhole tools for both directional telemetry and logging-while-drilling (LWD) applications, as part of the front line data acquisition system within the drilling process, has made reliability a prime area of importance. This paper presents and validates an existing model to predict severe damaging vibrations. It also provides analysis techniques and guidelines to successfully avoid the vibration damage to downhole tools and to their associated downhole assemblies when using hole enlarging tools, such as hole openers and underreamers. The dynamic analysis model is based on forced frequency response (FFR) to solve for resonant frequencies. In addition, a mathematical formulation includes viscous, axial, torsional, and structural damping mechanisms. With careful consideration of input parameters and the judicious analysis of results, we demonstrated that drillstring vibration can be avoided by determining the three-dimensional vibrational response at selected excitations that are likely to cause them. In addition, the analysis provides an estimate of relative bending stresses, shear forces, and lateral displacements for the assembly used. Based on the study, severe vibrations causing potentially damaging operating conditions that had been a major problem in nearby wells were avoided. Steps required to estimate the operating range of the drilling parameter such as weight on bit and rotational speeds to mitigate and avoid the downhole tool failures due to vibration are given. Extensive simulations were performed to compare the data from the downhole vibration sensors; this paper includes severe vibration incidence data from three case studies in which the model estimated, predicted, and avoided severe vibration (Samuel, R., et al., 2006, "Vibration Analysis Model Prediction and Avoidance: A Case History," Paper SPE 102134 Presented at the IADC India Conference, Mumbai, India, Oct. 16-18; Samuel, R., 2010, "Vibration Analysis for Hole Enlarging Tools" SPE 134512, Annual Technical Conference, Florence, Italy). [ABSTRACT FROM AUTHOR]

The paper presents a comprehensive review of the gas turbine hybrid vehicle (GTHV) under development at the University of Roma "Sapienza." A GHTV is an electric vehicle (traction entirely electric on 1 or 2 axles) equipped with a small turbogas operating as a range extender and -when needed- as a recharger for other auxiliaries. After a brief review of the history of the GTHV technology, a few configurations proposed in the past by different Authors are described and critically analyzed. Then, a complete feasibility assessment of a prototype configuration of a GTHV is presented and discussed in detail. Two possible implementations are studied: one for a small city car (peak power 4-8 kW) and one for a sport GT or passenger sedan (50-100 kW). All issues related to the system and component design, packaging, identification of the "optimal" hybridization ratio, performance of the conversion chain (gas turbine + batteries + electrical motor), kinetic energy recovery systems (KERS), mechanical and electric storage devices (flywheels, capacitors, advanced batteries), monitoring and control logic, compliance with the European vehicular ECE emission regulations, are explicitly addressed. One of the most important results of this analysis is though that there are several "nearly optimal" solutions and the final choice for a possible future industrialization would be dictated by manufacturing, commercial or marketing considerations. It because not only the system performance, but also the absolute and relative sizes (i.e., nameplate power) of the turbines and of the battery package depend substantially on the type of driving mission the car is required to perform. In the paper, both theoretical and practical issues are addressed, and on the basis of the analysis of the existing state of the art, it is argued that the GTHV is an environmentally friendly, technically and economically feasible product based on mature components. [ABSTRACT FROM AUTHOR]

The paper presents the results of a research regarding the application of cogeneration plants, based on organic rankine cycle (ORC), fed with wood residuals. In the first part of the paper an energy audit of the companies in a furniture industry district, located in the North-East of Italy, is presented. On the basis of these data a typical electricity/ thermal demand profile dependent on the number of employees has been determined. In order to evaluate the potential savings achievable with an ORC cogeneration plant, a numerical simulation model has been developed to analyse the energy balances of the components as well as the whole ORC power plant performance. The effects on the system energy and exergy efficiencies of different binary and ternary mixtures of poIisiloxane as working fluid and of different operating modes (cogeneration or pure electricity production) have been analysed, also in off-design conditions. [ABSTRACT FROM AUTHOR]

This paper presents an improved reservoir simulation approach to methane production in a longwall mining environment. The coal beds are naturally fractured systems with the gas adsorbed into the coal matrix. Fractures penetrating the coal matrix have limited storage capacity, but they play the role of a gas transportation system. The proposed simulation technique is based on the assumption that a mass of coal removed by mining transfers its gas to adjacent fractures. By using an ECLIPSE coal bed methane simulator, the pore volume of the matrix represents the coal volume of the simulation cell. Consequently, the exploitation of coal can be simulated by modifying the matrix pore volume over time. This paper presents theoretical backgrounds of this approach and investigates numerical effects. A case study of the Moszczenica coal mine in Poland, including computer simulations of methane production, is also reported to show that a long history of the methane and coal recovery can be reproduced using the proposed technique. [ABSTRACT FROM AUTHOR]

Governments are pursuing a variety of measures to reach common and more efficient environmental and energetic policies: Nonetheless, the effort has shown to be not sufficient, since the objectives stated in the European Union (EU) Directive 2009/28/EC on energy efficiency seem quite distant to be reached. A greater attention has obviously been paid toward the industrial sector, which utilizes a major share of primary energy consumption: Till now several actions have been taken to achieve the energy performance of buildings, but very few are in operations. Nonetheless, in order to be most effective, governments should focus their attention not only on energy intensive large enterprises (LEs) but also on nonenergy intensive small and medium enterprises (SMEs) that represent the majority of the total number of industries, cover a consistent share of the energy consumption of a whole domestic industrial sector, and are usually less efficient than LEs. This paper aims to highlight the most effective energy savings opportunities (ESOs) for reducing energy consumption in industrial operations that have been successfully implemented in a large number of SMEs case studies investigated in North America and Italy, showing a correspondence (in terms of savings and costs) between the two databases. This paper analyzes the ESOs, characterized by best available technologies and practices (BAT/Ps), with a cross-analysis within three manufacturing sectors, i.e., primary metals, plastics, and textiles, and considering different subsizes among SMEs, in order to show commonalities and differences among the sample. The ESOs have been analyzed and ranked according to different criteria of importance, highlighting the most diffused, those having the highest energy savings, and those with the shortest pay-back time. The scope of the elaboration of these criteria is twofold: on one side, it allows to be closer to the entrepreneurial sensibility, guiding entrepreneurs in evaluating a possible investment in energy efficiency; on the other side, it provides important suggestions for a public local authority that, through financial support and/or other policies, aims at diffusing the adoption of BAT/Ps and increasing the sectors' energy efficiency and competitiveness. [ABSTRACT FROM AUTHOR]

This paper provides an overview of the development and optimization of abrasive-slurry-jet methods for completion and stimulation applications. Abrasive particles added to the fluid dramatically reduced the system pressure requirements. The paper discusses the technical capabilities of cutting through various materials and .formations and also discusses improvements and proven applications. Abrasive fluid-jet systems are capable of cutting through rocks of all types, and with greater location control that is not susceptible to the geologically induced deviations encountered with mechanical methods. Abrasive fluid-jets drill rock through the erosion induced by very small particles which individually remove only small fragments but are in such numbers that the drilling rate is at or above that of conventional tools. The particles are powered by the velocity of the supporting fluid, generated in turn by pumps on the surface. The cutting occurs ahead of the nozzle body allowing the nozzle assembly to be fed in the tunnel to create drain-holes. Fluid-jet methods have the potential of improving completion and stimulation efficiency in heterogeneous formations such as fractured and/or vuggy carbonate reservoirs. Application for completion, stimulation and, even, well/platform abandonment has been successful. [ABSTRACT FROM AUTHOR]

There have been papers that analyze the relationship between bit design and a bit's vibrational characteristics. These papers typically are based on the analysis of three-axis near-bit down-hole vibration sensors. In this paper, the authors take a simpler approach. Using a standard microphone literally pointed at the bit, they record the noise of the bit/ rock interaction while drilling and analyze the resulting noise for these bit vibrational characteristics. The data were gathered at the Colorado School of Mines in Golden, CO. The noise of a PDC core, roller cone, and diamond core bits were recorded under various weight and rotary speeds using a microphone and a vertically mounted uniaxial geophone (used for confirming the data recorded on the microphones). Using a Fast Fourier Transform, the frequency spectra were extracted from the recorded data and analyzed. The data were normalized for rotational speed. The results of the frequency analysis of the roller cone, the PDC, and the natural diamond bits are presented in this paper. The major differences in the three bit frequency characteristics could be detected and furthermore, for drag bits, the frequency characteristics could be related to the bit's design. The frequency spectra of the roller cone bit can best be described with a general high amplitude level that is relatively evenly distributed over the whole frequency spectrum. The drag bit data showed a strong relationship between the number and arrangement of cutting elements and frequency peaks on a plot of amplitude versus cycles per revolution. Frequency peaks were observed at multiples of the number of cutting elements. In general this relationship was strongly visible on the PDC bit data but not as strongly visible on the diamond bit data. The conclusion is that bit characteristics can be determined using only the noise of a bit. Potential applications of this research include detecting and diagnosing bit problems (e.g., broken teeth and bit bailing) in real time using simple microphone based acoustic data. [ABSTRACT FROM AUTHOR]

This paper presents an analytic approach for defining optimal operation decisions for a power generation unit (PGU) in combined heating and power (CHP) systems. The system is optimized with respect to cost, and the independent variables are the thermal load and the electric load. Linear programming is a common tool used to find the optimal PGU operation for a given combination of thermal and electric loads, but these methods are more computationally intensive than the analytical approach proposed in this paper. The analytic process introduced in this paper shows that the optimal PGU operation for all possible thermal and electric loads can be decided by simple and explicit equations even when the efficiency of the PGU is allowed to vapy with PGU loading. Moreover, the analysis reveals that for all possible load conditions, the optimal CHP system operation is based on either following the electric load (FEL) or following the thermal load (FTL) strategies. The cost ratio, i.e., the ratio of the electricity price to the fuel price, is introduced as the key parameter used for making optimal decisions. Cost ratios in Chicago, IL and Philadelphia, PA are used as case studies to show the effect that different cost ratios have on the optimal operation decisions for each possible input load [ABSTRACT FROM AUTHOR]