bluuebunny/crossref_metadata_2025_split huggingface dataset:
Progress in Developing Commercial Fuel Cells
Authors: Fleming D.K. 
Published: December 2007

Abstract
The fuel cell concept is being developed for the economic production of electricity. The 6.5:1 cost differential in favor of residentially purchased fossil fuels over electricity provides the impetus for this work. This article surveys the current status of research and development on the many types of fuel cells and includes an extensive reference list.

Introduction
A major benefit of the current space exploration program has been the "fall-out" of technical advancements in many fields, which includes fuel cell research and development. Because space officials have determined that fuel cells in the power range of 100 w to 25 kw are the most economic power sources for space missions lasting from 1 day to several weeks, they have spent over $100 million for research in fuel cell technology. One result of this research is that a commercially economic fuel cell may soon be available.

What Is a Fuel Cell?
The Gemini flights have made most people aware that fuel cells exist, but they know little else about them. The very name fuel cell is a poor choice since it is not very descriptive of the use or operation of the device. In fact, the same term is used to describe a better gasoline tank on Indianapolis race cars, and here the name fits. Considering the operation of the device, a better name for it would be a "continuous battery". The National Electrical Manufacturers Assn. defines a fuel cell as an "electrochemical cell which can continuously change the chemical energy of a fuel and an oxidant to electrical energy by an isothermal process involving an essentially invariant electrode-electrolyte system." This NEMA definition describes a continuous battery that does not run down or require recharging and that will continue to operate as long as fuel and oxidant are fed to it. Like all batteries, fuel cells convert the chemical energy of the reaction directly to electrical energy without the intervening steps of heat and mechanical energies. Because the conversion of heat is not required, the fuel cell is not limited by the Carnot efficiency. The theoretically high efficiency of a fuel cell is possible because the reaction is nearly reversible. The fuel cell, which reacts hydrogen and oxygen w make water and electricity, is exactly the reverse of the electrolysis of water with electricity to make hydrogen and oxygen. The fuel cell has been described as a continuous battery. Fig. I compares the operation of a fuel cell to a lead-acid storage battery. Both devices consist of an anode (negative terminal) and a cathode (positive terminal). Both batteries use an ion-conducting electrolyte. The method of generating electricity is the same in both-the galvanic oxidation-reduction reaction. in the lead-acid battery, metallic lead is converted to lead sulfate at the anode, and electrons go out the negative terminal.
JPT
P. 749ˆ
Further Discussion of Application of Oil Muds
Authors: Benning M. J. 
Published: December 2007

Abstract
After reading Bloemendal's "Discussion of Application of Oil Muds" (Oct. 1986 SPEDE, Page 395), I felt compelled to reply. I have 6 years of experience with Dresser, Magcobar in various capacities, including mud engineer, instructor in the in-house schools, and finally technical service engineer. I was first based in south Texas and later in Houston, where I spent time in the field dealing with oil-based muds in Alaska, Wyoming, North Dakota, California, Texas, and Louisiana, both onshore and offshore. I will address Bloemendal's objections in the order in which they occurred.
Shortly after the higher-fluid-loss oil muds came into use, I put together a study comparing rates of penetration (ROP's) between oil-based and conventional (usually chrome lignosulfonate) muds in south Texas. I chose wells drilled in the same area, at the same depths, and as much as possible, with the same bits. None of the wells used a polycrystalline bit. Without a doubt, the oil-based muds outperformed the water-based fluids. Bloemendal attributes the increased penetration to higher API-FL, lower effective bottomhole density, better lubricity, and more favorable rheology. Undoubtedly, he is correct in his choice of possible reasons for the increased penetration. But why question the increased ROP with oil-based muds because of these factors? They are inherent in the oil-based system, and all these attributes are used as selling points for oil-based muds. That they are simply mechanical factors in no way negates their importance.
Bloemendal mentions the possibility of an oil-based mud flipping under certain circumstances. Flipping is the sudden change from a water-in-oil emulsion to an oil-in-water emulsion. He neglects to mention that these circumstances are extremely rare and usually avoidable. In my 6 years dealing with muds, I have seen a few in bad condition, but I have yet to see one flip.
On the Modeling of Vertical Permeability Barriers in Single-Well Simulation Models
Authors: Haldorsen Helge H. 
Published: December 2007

SummaryThis paper presents stochastic descriptive schemes for explicit and implicit modeling of vertical permeability barriers in single-well simulation studies. The drainage volume of the well to be simulated is first partitioned into two regions: one explicit region ("explicit" because actual barriers—e.g., shales of various sizes—are placed within the grid) and one implicit region ("implicit" because the effects of the discontinuous shales are averaged into an effective vertical permeability). Second, the shales are converted into vertical transmissibility modifiers and included in the data-input stream, along with the effective vertical permeabilities calculated for the implicit regions.The methodology developed is illustrated by application to a North Sea reservoir with a thin oil column sandwiched between a gas cap and an active aquifer. In this reservoir, trustworthy predictions of oil, gas, and water production rates through time are of fundamental importance. In fact, the field-development decision may be swayed one way or another, depending on how long the gas and water production may be suppressed (aided by shales) for a reasonably high (and sustainable) oil-production rate.
The Main Area Claymore Reservoir: A Review of Geology and Reservoir Management
Authors: Chen H. K. , Robinson T. , Harker S. D. , Maher C. E. 
Published: December 2007

Summary
The Main Area Claymore reservoir (MACR) is the major reservoir of the Claymore field, located 110 miles [177 km] northeast of Aberdeen in U.K. Block 14/19, offshore North Sea. An integrated team effort by geologists, geophysicists, and engineers has led to an increase in recoverable oil for the MACR. Concurrently, the MACR production increased from 47 to 57 MSTB/D [7472 to 9062 stock-tank m3/d] from mid-1984 to the end of 1986. The MACR is of Late Jurassic Age. Fine- to coarse-grained sandstones of the Sgiath and Piper formations are succeeded by the very-fine- to medium-grained sandstones of the Claymore sandstone member (CSM) of the Kimmeridge clay formation. The CSM constitutes the bulk of the MACR and is divided into two informal reservoir units: the low gamma ray sands (LGRS) and the high gamma ray sands (HGRS).
The principal early field problems were lack of sufficient pressure support, uneven water advancement in both the horizontal and vertical directions, and a large pressure gradient across the reservoir. Thus, more offtake and selective injection points were required to improve oil recovery. Growth of geological and engineering knowledge of the MACR has resulted from infill drilling and the integration of repeat formation tester (RFT) pressures, flowmeters, well logs, detailed core studies, and three-dimensional (3D) seismic. Increased current oil production and recoverable reserves are the consequences of this work.
To improve oil recovery, a 10-slot subsea template for water injection was installed in Summer 1985. Three subsea water injectors have been drilled from this template and five platform wells redrilled as producers to downdip areas of the MACR. The recent drilling program owes its success to the combined efforts of a multidisciplinary team, which resulted in the optimum placement of wells and the adoption of selective completion to optimize areal and vertical sweep efficiencies.
Some Theoretical Results Useful in Analyzing Well Performance Under Solution-Gas Drive
Authors: Camacho-V. R. G. , Raghavan Rajagopal 
Published: December 2007

Summary
This paper presents results pertinent to the analysis of well performance in solution-gas-drive systems. The characteristics of wells producing solution-gas-drive systems are documented. Procedures to correlate multiphase flow solutions with single-phase flow systems for both transient and boundary-dominated flows are presented.
Subsea Adjustable Choke Valves: A Focus on a Critical Component
Authors: Cyvas M. K. 
Published: December 2007

Summary
With emphasis on deepwater wells and marginal offshore fields growing, the search for reliable subsea production systems has become a high priority. A reliable subsea adjustable choke is essential to the realization of such a system, and recent advances are producing the degree of reliability required. Technological developments have been primarily in (1) trim material (including polycrystalline diamond), (2) trim configuration, (3) computer programs for trim sizing, (4) component materials, and (5) diver/remote-operated-vehicle (ROV) interfaces. These five facets are overviewed and progress to date is reported. A 15- to 20-year service life for adjustable subsea chokes is now a reality.
Another factor vital to efficient use of these technological developments is to involve the choke manufacturer and ROV/diver personnel in initial system conceptualization. In this manner, maximum benefit can be derived from the latest technology.
Major areas of development still required and under way are listed, and the paper closes with a tabulation of successful subsea choke installations in recent years.
Failures of Nickel/Copper Bolts in Subsea Application
Authors: Wolfe L. H. , Joosten M. W. 
Published: December 2007

Summary
Slow-strain-rate tests in ASTM seawater using specimens prepared from a failed nickel/copper-alloy bolt have shown that precipitation-hardened UNS N05500 (Monel K-500®) is embrittled by cathodic protection with sacrificial aluminum anodes. Some loss of ductility also occurred when annealed UNS N05500 was coupled to aluminum anodes and when the hardened alloy was coupled to steel. Brittle fractures produced by slow-strain-rate tests were intergranular and were very similar in appearance to the field fractures. While the slow-strain-rate tests were conducted on an alloy from only one source, there is no reason to assume that UNS N05500 alloy from other sources would resist hydrogen embrittlement from standard cathodic protecti.on systems.
Relationship Between Cement Slurry Composition, Mechanical Properties, and Cement-Bond-Log Output
Authors: Jutten J. J. , Guillot D. , Parcevaux P. A. 
Published: December 2007

Summary
This paper describes and quantifies the influence of cement slurry composition on the mechanical properties of the hardened cement and on the cement bond log (CBL). Laboratory experiments were performed on more than 20 different cement slurry formulations with densities ranging from 1200 to 2280 kg/m3 [10 to 19 lbm/gal]. Results show that (1) CBL attenuation rate is directly related to the acoustic impedance of the cement; (2) particulate extenders like silica microspheres provide, for a given slurry density, higher acoustic impedance and CBL attenuation rate than chemical extenders like soluble silicates; (3) latex in the cement does not influence the CBL; (4) the relationship between compressive strength and velocity of compressional waves, verified for most slurries, is not valid for salt-containing slurries; and (5) a single relationship exists between Young's modulus and Poisson's ratio.
Capacitance Effects in Porous Media
Authors: Jasti Jay K. , Vaidya Ravimadhav N. , Fogler H. Scott 
Published: December 2007

SummaryThe velocity dependence of parameters in the Coats-Smith model for tracer dispersion and tailing in porous media was investigated. An axisymmetric pore with a step change in cross-sectional area was used as a model system to determine whether the stagnant zone resulting from variations in flow cross sections contributes to the observed capacitance (i.e., tailing) at the pore level. Numerical simulations show that eddies with recirculation flow are formed in the pockets as a result of flow separation. The tracer transport between the eddies in the dead zones and the main channel was found to be diffusion-limited. The simulations reveal that in the Stokes flow regime, the mass-transfer coefficient between the two regions is independent of the interstitial velocity, in contradiction to earlier theories.Coreflood experiments were performed with radioactive tracers to verify the hypothesis that the capacitance effects are not the result of a change in flowing fraction. The experimental results confirm that tracer tailing is a function of the ratio of the molecular diffusivity to the flow rate. in light of these findings, we investigated the validity of the Coats-Smith model to predict dispersion and tailing in a porous medium. Our studies show that the Coats-Smith model may be used; however, certain restrictions, described in this paper, apply to the procedure for estimation of parameters.
Evaluation of Key Reservoir Drive Mechanisms in the Early Cycles of Steam Stimulation at Cold Lake
Authors: Denbina E. S. , Boberg T. C. , Rotter M. B. 
Published: December 2007

Summary
A history-matched, 2D, single-well numerical model was used to evaluate the contributions of four key drive mechanisms to early cyclic-steam-stimulation (CSS) oil recovery at Cold Lake, Alta. Formation compaction was found to be by far the dominant producing mechanism. Solution-gas drive was the most important of the remaining mechanisms. Fluid expansion had a relatively minor role. Gravity drainage accounted for little of the oil produced in the first two cycles, but increased in importance in subsequent cycles.
Pressure-Transient Testing of Water-Injection Wells
Authors: Abbaszadeh Maghsood , Kamal Medhat 
Published: December 2007

Summary
This paper presents an interpretation method for injectivity and falloff testing in a single-layer oil reservoir that is under waterflooding and develops analytical solutions for pressure and saturation distributions. The effects of relative permeability, wellbore storage, and skin are considered in these solutions. New field-dependent type curves for falloff tests, which exhibit features that do not appear in the currently available single-phase-flow type curves, are also presented. Matching of field data on these curves yields fluid mobilities in various banks, skin, formation permeability, and flood-front location. Field data interpretation with the new method shows that falloff tests can be used to monitor the progress of waterfloods.
Performance of Wells in Solution-Gas-Drive Reservoirs
Authors: Camacho-V. R. G. , Raghavan R. 
Published: December 2007

Summary
We examine buildup responses in solution-gas-drive reservoirs. The development presented here parallels the development for single-phase liquid flow. Analogs from pseudopressures and time transformations are presented and gas-drive solutions are correlated with appropriate liquid-flow solutions. The influence of the skin region is documented. The basis for the success of the producing GOR method to compute the saturation distribution at shut-in is presented. The consequences of using the Perrine-Martin analog to analyze buildup data are discussed.
Frequency Effects in Acoustic Logging
Authors: Medlin W. L. 
Published: December 2007

Summary
Variable-frequency acoustic logs were obtained in soft and hard formations by use of tone-burst driving methods with broad-band acoustic sources. Two underwater sources–a bender bar and a flexural disk device–were used as logging-tool transmitters. By driving the source with three-cycle tone bursts, we produced short-duration, monotone radiation in the wellbore at each resonance frequency. In this way, logs were run at each of many driving frequencies covering the acoustic band.
Our experiments dealt with the frequency effects of mode excitation (cutoff frequencies) and the frequency content of received waves. Fourier transforms of the waveforms were used to investigate the frequency content of received waves.
Effects of Steam/Liquid Counterflow on Pressure-Transient Data From Two-Phase Geothermal Reservoirs
Authors: Bodvarsson Gudmundur S. , Cox B. Lea , Ripperda M. 
Published: December 2007

SummaryNumerical studies were performed to investigate the effects of localized feed zones on the pressure transients in two-phase reservoirs. Gravity effects were shown to affect the pressure transients significantly because of the large difference in the densities of liquid water and vapor. Production from such systems enhances steam/liquid-water counterflow and expands the vapor-dominated zone at the top of the reservoir. Subcooled liquid regions develop in the center of the reservoir as a result of gravity drainage of cooler liquid water. The vapor zone acts as a constant-pressure boundary and helps to stabilize the pressure decline in the system. The pressure transients at observation wells were shown to depend greatly on the location (depth) of the major feed zone; if this is not accounted for, large errors in deduced reservoir properties will result. At shallow observation points, pressures may actually increase as a result of enhanced steam upflow caused by production at a deep feed zone.
Simulation of Downhole Heater Phenomena in the Production of Wellbore Fluids
Authors: Sharma Yugdutt , Shoham Ovadia , Brill James P. 
Published: December 2007

Summary
A model is presented for predicting the pressure and temperature profiles for gas/liquid flow in wellbores stimulated with downhole heaters. The solution algorithm consists of coupling the momentum- and energy-balance equations for the wellbore fluids with the transient behavior in the surrounding rock. The heater is treated as a source term in the energy-balance equation. The model is capable of predicting wellbore thermal effects, such as reduction of fluid viscosity and increase of free gas. It can be used to simulate temperature maintenance during well shut-in periods to prevent pour-point problems and paraffin or hydrate formation. An existing well with production problems related to thermal effects was simulated by the model. Results indicate that wellbore temperatures can be controlled by downhole heaters. Also, under certain conditions, an increase in production was predicted with such an application.
Expanding the Range for Predicting Critical Flow Rates of Gas Wells Producing from Normally Pressured Waterdrive Reservoirs
Authors: Upchurch Eric R. 
Published: December 2007

Summary
The critical flow rate of a gas well is the minimum flow rate required to prevent accumulation of liquids in the tubing. Theoretical models currently available for estimating critical flow rates are restricted to wells with water/gas ratios less than 150 bbl/MMcf [0.84 × 10−3 m3/m3]. For wells producing at higher water/gas ratios from normally pressured waterdrive reservoirs, a method of estimating critical flow rates is derived through use of an empirical multiphase-flow correlation.
A Robust Prediction Method for Rapid Phase-Behavior Calculations
Authors: Varotsis N. 
Published: December 2007

Summary
The success of phase-behavior calculations based on an equation of state (EOS) depends to a great extent on the quality of the selected initial estimates of the independent variables. Estimates considerably different from the final answer often lead to either trivial solutions or convergence problems.
The method presented in this paper consists of obtaining the maximum possible information concerning the vapor/liquid equilibrium of the mixture by directly solving the selected EOS before the start of the main iterative calculation. The information obtained, with minimal computational cost, is subsequently used to initiate a Newton-type iterative method that is stable and converges rapidly toward the solution when good estimates are provided.
Analysis of the Transient Production of a Thermally Stimulated Well
Authors: Bidner M. Susana , Kostiria Horacio M. , Vampa Victoria C. 
Published: December 2007

Summary
This paper presents a simple mathematical model to predict the oil production rate from a cyclic-steam-stimulated well. The oil volume flowing from the cold zone is estimated by numerically solving the diffusivity equation governing the radial transient flow of a fluid with a small and constant compressibility for three outer boundary conditions—infinite medium, constant pressure, and no flow—corresponding to different reservoir types. At the interface between the cold and hot zones, pressure is calculated by means of the superposition principle. Numerical solutions give pressure distribution as a function of radius and time. They also allow assessment of the effects of transient flow and outer boundary conditions on oil production rate. The numerical response of a cycle of steam injection strongly depends on the outer boundary condition. Excellent agreement is found between model-calculated and observed field rates.
Gas Composition Shifts in Devonian Shales
Authors: Schettler P. D. , Parmely C. R. 
Published: December 2007

Summary
Analysis of the gas composition of Devonian shale wells indicates that the composition of produced gas shifts during the production history of the well. Possible mechanisms to explain this behavior are examined in light of field and laboratory data. Application of diffusion theory is made to explain adsorption-like behavior exhibited by some shales.
Downhole Simulation Cell Shows Unexpected Effects of Shale Hydration on Borehole Wall
Authors: Simpson Jay P. , Dearing H. L. , Salisbury D. P. 
Published: December 2007

Summary
Previous attempts to predict the effects of drilling fluids on borehole stability in shale have been unsatisfactory. This paper describes laboratory equipment capable of simulating downhole conditions to permit evaluation of drilling fluids by testing the alteration of natural shale specimens when drilled and exposed to drilling fluid under an annular flow regime for an extended period of time. The paper discusses ramifications of the shale alteration relative to such operational problems as torque, drag, and stuck pipe.