J. Energy Resour. Technol. 2006;128(4):245-246. doi:10.1115/1.2358150.

The 17th Century, the so-called Age of Reason, is distant from us in nearly every respect: dress, politics, thought, and, of course, time. The collection of philosophers that wrote then can seem out of touch today. But perhaps we just need a refresher.

Commentary by Dr. Valentin Fuster


J. Energy Resour. Technol. 2006;128(4):247-256. doi:10.1115/1.2358139.

The present paper studies the effect of mandrel pop out on the dynamics of a solid tubular submerged in fluids of a typical vertical wellbore. A mathematical model describing the stress and pressure waves within the tubular-fluid system (inner and outer fluids as well as solid tube) has been developed. The model takes into account the coupling effect of the three mediums. A specific case of a 127mm solid tubular, placed inside a 340mm borehole with different inner and outer fluids was considered. An analytical solution of the developed model was obtained. It was found that the excitation of the system splits into several components and propagates within the three mediums. In addition, the coupling effect revealed modification in the normal waves’ speeds and frequencies as compared to the uncoupled solution and identifies associated natural frequencies. Moreover, it was noticed that the maximum vibration occurs at the free end of the tubular and that the tube may experience local buckling in the neighborhood of the fixed end.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):257-267. doi:10.1115/1.2358140.

This work presents a mathematical method to design complex trajectories for three-dimensional (3D) wells. Three-dimensional cubic trajectories are obtained for various end conditions: free end, set end, free inclination/set azimuth, and set inclination/free azimuth. The resulting trajectories are smooth continuous functions, which better suit the expected performance of modern rotary steerable deviation tools, in particular point-the-bit and push-the-bit systems. A continuous and gradual change in path curvature and tool face results in the smoothest trajectory for 3D wells, that in turn results in lower torque, drag, and equipment wear. The degree of freedom and the associated parameters of the 3D curves express the commitment between the average curvature to the final length of the path, which can be adjusted to fit the design requirements and to optimize the trajectory. Several numerical examples illustrate the various end conditions. The paper also presents the full mathematical results (expressions for the 3D path, actual curvature, and actual tool face). The method is directly applicable to the well planning cycle as well as to automatic and manual hole steering.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):268-274. doi:10.1115/1.2358141.

Drillstring vibrations and in particular stick-slip and bit-bounce are detrimental to oil-well drilling operations. Controlling these vibrations is essential because they may cause equipment failures and damage to the oil-well. A simple model that adequately captures the dynamics is used to simulate the effects of varying operating conditions on stick-slip and bit-bounce interactions. It is shown that the conditions at the bit/formation interface, such as bit speed and formation stiffness, are major factors in shaping the dynamic response. Due to the varying and uncertain nature of these conditions, simple operational guidelines or active rotary table control strategies are not sufficient to eliminate both stick-slip and bit-bounce. It is demonstrated that an additional active controller for the axial motion can be effective in suppressing both stick-slip and bit-bounce. It is anticipated that if the proposed approach is implemented, smooth drilling will be possible for a wide range of conditions.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):275-279. doi:10.1115/1.2358142.

The drive for energy independence has created a window of opportunity for innovations in oil recovery. New artificial lift methods like progressing cavity pumping have been successfully applied to downhole pumping applications. The multilobe pumps are also making inroads into the industry to be used under different operating conditions. Although the design has been mainly based on empirical standards and trial and error modifications, a more phenomenally optimum design of the pump is required to achieve a high efficiency standard. The optimal relationship between the pitch and the diameter of the housing is obtained to achieve a maximum flow rate for multilobe pumps.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):280-289. doi:10.1115/1.2358143.

The effective application of continuous gas lift entails solving the combinatorial optimization problem of optimally allocating limited resources. This work proposes a mixed integer linear formulation for the problem of maximizing oil field profit under multiple facility constraints such as limited lift gas, fluid handling, and storage capacities. Families of valid inequalities are identified and introduced into the basic model to render a stronger formulation. Numerical experiments using commercial and non-commercial software, and comparisons with published results, show that the proposed method yields fast solution with significant average increase in oil production rate and profit.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):290-299. doi:10.1115/1.2358144.

With growing understanding of the differences between solid residues from the fluidized bed combustion of petroleum coke and of coal, the significance of fuel-derived and sorbent-derived components of the ash has become clearer. It is well documented that hydration of the ashes is necessary prior to disposal or utilization or as a reactivation method. Initially, hydration of the lime was thought to involve water reacting only with CaO to form Ca(OH)2 but when the free lime content of the ashes is looked at before and after hydration, it is apparent that the process is more complex. Detailed analyses have shown that the free lime can decrease and vary within the same ash in different particle size ranges. The complexity of the reactions is reflected in problems with the assessment of the free lime content of the materials and the effect of hydration on different particle size fractions of the ash. The free lime content of the ash is significantly lower than expected based on the elemental analysis. Bed ash from the circulating fluidized bed combustion boilers owned and operated by the Nelson Industrial Steam Company Ltd. (NISCO) was examined in detail to elucidate the fate of calcium in the ash during hydration, using a range of techniques. The objective of the study is to determine the amount of CaO available for hydration/reactivation and to better understand interactions of Ca and other mineral components of the ash. Analysis results indicate that in NISCO ashes up to about 6% of the analytical CaO may be combined as acid soluble and insoluble OCCs (other calcium compounds). This implies up to about 10% less free lime than would be inferred from standard chemical analyses. About 1% of the missing CaO can be present as acid insoluble Ca and Mg vanadates, with up to 2% bound in soluble OCCs. The remaining 34% is still not accounted for. It is clear that even very minor quantities of mineral matter, other than CaO or CaSO4, associated mainly with the coarser size fractions, are important. The amount of bound water in the hydrated ash, other than that combined in portlandite or brucite, can be as large as 35%. This cannot be ignored when sample mass change on hydration or heating is used as a measure of the extent of CaO to Ca(OH)2 conversion.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2005;128(4):300-310. doi:10.1115/1.2358145.

Relative effects of buoyancy and momentum on the characteristics of horizontally oriented circular (Circ) and elliptic (E) burner flames in a quiescent environment over a wide range of jet exit velocities are presented. The major axis of the elliptic burner was oriented horizontally and vertically (referred to as Emaj and Emin flames, respectively). Propane was used as fuel and a small amount of hydrogen was piloted to attach flames to the burner. Global flame characteristics such as flame dimensions, centerline trajectory, emission indices (EI) and radiative fraction, and in-flame transverse concentration and temperature profiles were measured. At a jet exit Reynolds number (Rej) of 2000, based on the area-equivalent diameter of the burner, the flame characteristics were affected by the burner geometry and its orientation. Also, the vertical dimension of the burner exit dictated buoyancy effects. At Rej=12,500, the influence of burner geometry or its orientation was negligible. Elliptic burner flames exhibited lower liftoff and blowout velocities than circular burner flames. Furthermore, the flame stability and nitric oxide emissions were not much affected by the orientation of elliptic burner. Although the elliptic burners produced higher EINO at lower jet exit velocities, the variation in EINO among three burners (Circ, Emaj, and Emin) was insignificant at higher velocities. Some effects of buoyancy on EICO were observed at lower jet exit velocities and the EICO was the lowest for the burners with largest buoyancy flux. Elliptic burner flames produced greater peak flame temperature than the corresponding circular burner flames under most conditions.

Topics: Flames , Emissions , Buoyancy
Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2005;128(4):311-318. doi:10.1115/1.2358146.

Circulating fluidized bed (CFB) boiler has entered electric power industry field because of burning a wide range of fuels, while still achieving strict air emissions requirements. This study focuses on a 300MW CFB boiler, which will be one of the largest CFB boiler in the world. In a CFB boiler, fuels were burned with the addition of limestone to capture SO2 in a solid form. Therefore, the volume of ashes, both bottom ash and fly ash, discharged from a CFB boiler is much higher than the ashes discharged from a pulverized coal-fired (PC) boiler at the same capacity of the boiler. CFB boiler ash cannot be used as a cement replacement in concrete due to its unacceptably high sulfur content. The disposal in landfills has been the most common means of handling ash in circulating fluidized bed boiler power plants. However, for a 300MW CFB boiler power plant, there will be 600,000tons of ash discharged per year and will result in great volumes and disposal cost of ash byproduct. It was very necessary to solve the utilization of CFB ash and to decrease the disposal cost of CFB ash. The feasible experimental study results on the utilization of the bottom ashes of a 300MW CFB boiler in Baima power plant in China were reported in this paper. The bottom ashes used for test came from the discharged bottom ashes in a 100MW CFB boiler in which the anthracite and limestone designed for the 300MW CFB project was burned. The results of this study showed that the bottom ash could be used for cementitious material, road concrete, and road base material. The masonry cements, road concrete with 30MPa compressive strength and 4.0MPa flexural strength, and the road base material used for base courses of the expressway, the main road and the minor lane were all prepared with milled CFB bottom ashes in the lab. The better methods of utilization of the bottom ashes were discussed in this paper.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):319-324. doi:10.1115/1.2358147.

A study of the characteristics of turbulent lifted-jet flames in the hysteresis regime was performed using methane and ethylene fuels in laminar and turbulent air coflows. Reattachment velocities and lifted flame heights just prior to reattachment vary linearly as for laminar flames in coflow. The flow regime of the coflow (i.e., laminar or turbulent) did not appear to affect the behavior of these flames. These observations are of utility in designing maximum turndown burners in air coflow, especially for determining stability criteria in low fuel-flow applications.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2005;128(4):325-334. doi:10.1115/1.2131886.

The use of a novel 3-port condensing wave rotor is suggested to enhance the turbocompression in a refrigeration cycle that works only with water (R718) as a refrigerant. Although the implementation of such a wave rotor essentially reduces the size and cost of R718 units, their efficiency may also be increased. The condensing wave rotor employs pressurized water to pressurize, desuperheat, and condense the refrigerant vapor, all in one dynamic process. The underlying phenomena of flash evaporation, shock wave compression, desuperheating, and condensation inside the wave rotor channels are described in a wave and phase-change diagram. The thermodynamic process is shown in pressure-enthalpy and temperature-entropy diagrams. Based on the described thermodynamic model, a computer program was generated to evaluate the performance of R718 baseline and wave-rotor-enhanced cycles. The effect of some key parameters on the performance enhancement is demonstrated as an aid for optimization. A performance map summarizes the findings. It shows optimum wave rotor pressure ratio and maximum relative performance improvement of R718 cycles by using the 3-port condensing wave rotor.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):335-342. doi:10.1115/1.2358148.

Thermoeconomic diagnosis procedures in the literature rely on the assumption that specific consumptions of resources in the components are the key to interpret the effects of malfunctions and then to trace a path towards the sources of anomalies. The main obstacle to a successful application of these approaches is represented by the actual interactions existing among components which cause a propagation of the alteration of component specific consumptions and therefore mask those effects that would allow a direct identification of the origin of malfunction. This paper presents an extensive discussion of potentialities and limits of diagnosis procedures proposed in the literature in distinguishing the effects induced by component interactions from those that are intrinsically generated by the anomaly, which is considered here as the main task to locate effectively causes of malfunctions in energy systems.

Commentary by Dr. Valentin Fuster


J. Energy Resour. Technol. 2005;128(4):343-345. doi:10.1115/1.2358151.

Magnetic materials in the drilling fluid used for drilling a petroleum well can significantly shield the Earth’s magnetic field as measured by magnetic sensors inside the drilling pipe. This has been shown to sometimes cause significant errors in the accuracy of borehole positioning using magnetic surveying. In this paper we present a physical approach for correcting the measured magnetic fields for such shielding. An explicit solution of the shielding problem is derived for the simplest case of a magnetic sensor on the axis of the borehole.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2006;128(4):346-351. doi:10.1115/1.2358149.

The paper analyzes the links among energy, economy, and the natural environment. This matter requires the reconsideration of energy efficient and low emission technologies and the definition of new instruments for the analysis of energy systems as well as for the definition of energy policies. After an overview of the methods available in the literature, dealing with a multidimensional analysis of energy system, the authors propose a quantitative approach based on the use of two different thermodynamic based utility functions. The utilization of those functions permits to join thermodynamic and environmental performance of the energy system, to analyze the effects of their interaction and to obtain a more logical comparison among different energy systems, accepting the multidimensional nature of the problem but maintaining a system analysis in the way engineers are accustomed to. Two cases are discussed and analyzed.

Commentary by Dr. Valentin Fuster

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