bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Temperature, Salinity, and Alcohol on the Critical Micelle Concentration of Surfactants
Authors: Noll L. A. 
Published: December 2007

ABSTRACT
Surfactants are used at high temperatures as additives for steamfloods, and in high-temperature surfactant floods. Most surfactants must be above the critical micelle concentration (CMC) in order to have appropriate properties for forming foams or mobilizing oil. The CMC of a surfactant increases dramatically at high temperatures; thus, it is important to know this value at the temperature of application for economical engineering design.
The CMC's of a series of surfactants as a function of temperature in the range 77°-392° F (298-473 K) have been determined at high temperatures from heats of dilution, a novel application of calorimetry. Enthalpies of dilution were determined at ambient and elevated temperatures. Surface tension measurements at ambient temperatures served to confirm the assignment of CMC from the heat of dilution data.
The CMC's of a pure surfactant were determined in distilled water, in aqueous solutions of NaBr up to 10% salinity, in n-butyl alcohol solutions up to 4% alcohol concentration, and at temperatures of 122° through 347° F (323-448 K). In general, CMC increased with an increase in temperature. The presence of electrolyte at a fixed temperature lowered the CMC and increased the sharpness of the onset of micellization. At 212° F (373 K), the presence of n-butyl alcohol caused the CMC to be lowered but had little effect on the sharpness of micellization. At 347° F (448 K), the alcohol had very little effect on the CMC, apparently because of the change in water properties at high temperatures.
The CMC's and solution behavior of three commercial surfactants were determined at 77°, 257°, and 392° F (298, 398, and 473 K), with no added salt. The CMC for these commercial surfactants also increased with temperature.
Quality Control of Sales Gas and Gas Treatment Units
Authors: Thiebot B. 
Published: December 2007

ABSTRACT
A major problem for the producers on a gas production site is encountered when a unit does not perform at its designed operating conditions. A consequence of this problem is, for example, a sales gas refused as not meeting specifications.
This paper illustrates that it is possible to solve this problem, i.e. to identify the faulty equipment, and to optimize the gas treatment process. This was realized for some gas fields, with the help of a small appraisal on the site completed by fluids samplings and numerical simulations of the process (Peng Robinson equation of state).
In one case, the sales gas was refused as not meeting specifications. An appraisal performed on the site by a small team showed that it was indeed the case and identified the faulty equipment.
In an other case, a quality control of operating conditions was performed on the main separators of a production unit, comparing for each separator its operating efficiency to the designed one.
In both cases, the experimental measurements justified fluid samplings on the site. Detailed analyses on the treated gas were then carried out in the laboratory, up to C18+ fraction, which permitted a quite successfull simulation of the process, especially at low liquids carry over.
The results of this study is that optimization of the process has been obtained with the establishment of operating tables. Such a table gives to the operator, for a given separator and a given value of its efficiency, the operating pressure and temperature to be run in order to give to the treated gas its commercial specification.
The Interaction of Small and Medium Scale Heterogeneities from a Shallow Marine Depositional Environment with Various Two Phase Displacements
Authors: Opdal Svein Tore , Kossack Charles A. , Lewis Jonathan J. M. 
Published: December 2007

Abstract
The interaction of rock heterogeneities with the two phase displacement of oil is the dominant factor in the recovery of oil. In general, reservoir simulation can describe this interaction, but due to the large grid blocks required in most field applications, the interactions of the fluid flow with small and intermediate scales of heterogeneity is neglected. The question of the importance and magnitude of this interaction is investigated in this paper. The shallow marine depositional environment was chosen for this study. A typical shallow marine deposit was dissected into five scales of heterogeneity. A numerical flow field containing small and medium scales of heterogeneity was created for the numerical simulation of fluid displacements. Two alternate numerical flow fields were created by the homogenization of this detailed description. The first "averaged" description consisted of homogeneous layers between the clay drapes. The final description was completely homogeneous. A series of displacements at various combinations of mobility ratios, viscous to gravity ratios and viscous to capillary ratios were simulated in all three numerical descriptions. A comparison of the results shows the interaction of the scales of the heterogeneity with the two phase flow of fluid and demonstrates where homogenization of the permeability variations introduces large errors in the simulation of oil recovery. This type of analysis can easily be applied to any depositional environment.
Sequential Staging of Tasks: A New Approach to Parallel Computations
Authors: Briens Frederic J. L. , Wu Ching H. , Gazdag Jeno , Wang Hsuan H. 
Published: December 2007

Abstract
Developing an efficient algorithm for solving a large linear system in parallel computing environments is the major problem associated with the application of parallel processing to a large-scale reservoir simulation. This paper presents a new algorithm called Sequential Staging of Tasks (SST) that fully exploits the capabilities of parallel supercomputers to speed-up the solution of a large linear system. The SST technique can use any number of parallel processors, keeps a good load balance, and preserves vector speed-up. As SST makes use of readily available iterative solvers, it also provides a surprisingly low implementation complexity. In our computer experiments, the SST technique yields a 5.6 speed-up with 6 processors when solving a 50,000-cell linear system.
A Mixing Law to Model the Dielectric Properties of Porous Media
Authors: Rodriguez Adolfo , Abreu Raul 
Published: December 2007

ABSTRACT
A new mixing law has been developed to model the dielectric properties of saturated porous media. The total propagation time of an electromagnetic wave through the composite porous medium is expressed as the sum of the propagation times through each component (rock, water and oil). A power dependence is established between the propagation lengths and the volume fractions for each component, and is expressed in terms of a water saturation exponent βw, an oil saturation exponent βn, and a βg exponent corresponding to the rock matrix material. The mixing law predicts all the major features of the measured frequency (ω) dependent dielectric constant as a function of water saturation. We conclude that the rapid increase of the dielectric constant at low water saturation values is consistent with βw ~ 0.3, while a decrease at high water saturations is indicative of βn &lt; 1. The hysteresis observed in the dielectric constant during imbibition and drainage is associated with the existence of a different βn for each process. We further show that the exponent corresponding to the water fraction is related to the Archie exponents in the low frequency limit. Reported experimental data at two different frequencies were used to establish the values of the model parameters at those frequencies.
Identification of Asphaltene Deposition in Camorim Field, Northeastern Brazil
Authors: de Andrade Brüning Inái M. R. , Martinez Ângela Vega , Travalloni Ana Maria L. 
Published: December 2007

ABSTRACT
Camorim field lies on the Continental Shelf of Sergipe Basin, under 12-21 m water depth. Its oil production started in July, 1976 with 300 m3/day; in 1978 it reached 800 m3/day and slowly decreased to 400 m3/day in 1982.
In order to identify causes for the decreasing oil production, a study involving twenty-three wells was carried on. The produced oils were characterized according to their properties and composition. The oils are of paraffinic and intermediate base and their gravities range from 39 to 17 API, being all crudes extremely rich in the gasoline fraction. Asphaltene contents vary greatly from 0.13 to 11.6% by weight. Gas chromatographic fingerprints, the asphaltene contents, interfacial tension and polarity determinations identified asphaltene deposition as the main cause for the low production rates. The analyses showed that the heavier and high asphaltenic crudes were highly unstable because the intermediate fractions which should stabilize the oil were present at low contents. Furthermore, polarity determinations showed direct correlation to asphaltene contents for several oils. This result led to the conclusion that the other oil polar components, the resins, which serve as peptizing agents for asphaltenes did not contribute to the polarity effects. This fact increases the instability of the oils and provides additional favourable conditions for asphaltene precipitation.
The case of three wells which undergone several stimulation treatments is described and confirmed the asphaltene deposition.
Use of Production Data to Estimate the Saturation Pressure, Solution Gor, and Chemical Composition of Reservoir Fluids
Authors: Labedi Rafa Mohamed 
Published: December 2007

ABSTRACT
This paper seeks to overcome the shortcomings of previous correlation work on PVT. More than a hundred oil samples were collected from three major oil producing countries in Africa -- Libya (97 samples), Nigeria (27), and Angola (4). PVT data on samples analyzed and correlations established.
Equations were developed using multiple regression analysis to predict the saturation pressure, the solution gas-oil ratio, and the chemical composition of oil reservoir fluids in the three countries. A new equation was developed for estimating gas gravity, which eliminates the need to know the gas gravity for predicting saturation pressure.
The developed correlations are functions of easily measurable field data such as first-stage separator pressure and temperature, producing gas-oil ratio, stock-tank oil gravity, and reservoir pressure and temperature.
They were found to adequately fit with random PVT data in the available literature and to be more practical and accurate than other techniques such as those used by Standing Glaso2, and Vasquez3. Moreover, they may be applied to other geographical areas.
Desalting Heavy Crude Oil by Counter-Flow Electrostatic Mixing
Authors: Warren Kenneth W. 
Published: December 2007

ABSTRACT
Removal of salt from heavy crude oils has always been problematical due to the difficulty in obtaining sufficient mixing for proper contact between the dilution water and dispersed brine without creating emulsions too stable for separation. As heavy oil resources have become more important in meeting world oil demand, advanced catalyst systems have been developed to increase the yield of useful products from a barrel of heavy crude. However, these catalysts demand stringent salt removal specifications in order to achieve sufficient process life for economic justification. Salt levels of less than one pound per thousand barrels of crude oil are often specified. Conventional desalting techniques are marginal at best when applied in these circumstances.
Electrostatic mixing technology is now beginning to find application in heavy crude oil desalting where it can achieve suitable contact efficiency for salt removal without producing unresolvable emulsions. This technique uses electric fields to apply mixing energy to the polar aqueous phase without expending energy on shearing of the bulk oil phase. When combined with counter-current flow of the oil and dilution water, electrostatic mixing produces multiple contact stages with their associated high efficiency in a single vessel.
Production of High Quality Crude Oil From Northern Great Plains Province Coal
Authors: Cochran Neal P. 
Published: December 2007

Introduction
The most abundant fossil fuel reserve in the U. S. is in the form of coal. This resource constitutes over 80 percent of our recoverable fossil fuel energy—some four times the quantity of all the oil, gas, tar sands, oil shale, and bituminous rocks combined. About 40 percent of this lies in the Great Plains deposit as lignite, subbituminous and Plains deposit as lignite, subbituminous and bituminous coal. This paper projects a potential process for recovery of high quality potential process for recovery of high quality crude oil from these coals and presents an estimate of cost for a commercial-scale plant.
The process to be used in this plant of the future is an outgrowth of work done by industry and Government, some of which is currently under way. A substantial portion of this work was performed for the Office of Coal Research and has been reported elsewhere. Estimated costs have been extracted from Office of Coal Research reports modified to reflect scale and more recent process improvements.
To obtain a good relationship of processes, we have chosen from OCR contracts with Consolidation Coal Co- [Continental Oil], The Pittsburgh and Midway Coal Mining Co. [Gulf Oil Pittsburgh and Midway Coal Mining Co. [Gulf Oil Co.], Arco Chemical Co. (Atlantic Richfield], FMC Corp., Hydrocarbon Research, Inc., The M. W. Kellogg Co., Institute of Gas Technology, Westinghouse Electric Corp., West Virginia U., Iowa State U., Pennsylvania State U. and the U. of Utah. Work performed by the Bureau of Mines has been considered, along with work on advanced power cycles by Avco Corp. and American Electric Power. No claim is made that these organizations endorse or subscribe to this projected plant. In fact, a number of the projected plant. In fact, a number of the estimates are somewhat more pessimistic than those from the companies. Some, however, are more optimistic. We should like to call the over-all projection "realistically conservative".

THE RESOURCES
In considering methods to put the nation's coal resources to their best use, one immediately thinks of both other energy resources and markets and concludes that the major effort must be in the field of energy. This means that the coal processing plant of the future will be large—comparable in size to a modern petroleum refinery—with a nominal capacity of 100,000 to 200,000 B/D, with the coal mine serving the plant being very large by today's standards. plant being very large by today's standards. The process requires large reserves for which many Western deposits are ideal—a large reserve can be put together, the coal quality is good for a number of processes, and, perhaps most important, the coal seams are ideally suited to the most efficient modern mining methods. Many of the coal seams are 75 to 100 ft thick, with little overburden.
Higher-Order Implicit Flux Limiting Schemes for Black Oil Simulation
Authors: Rubin B. , Blunt M. J. 
Published: December 2007

Abstract
Conventional Black Oil models normally use single point upstream weighting for mobility terms. This is known to give rise to significant levels of numerical dispersion. Several higher order schemes including Godunov's scheme, Flux Corrected Transport, and two-point upstream mobility weighting have been suggested for use in explicit or IMPES simulators to improve accuracy. FCT and Godunov's scheme cannot easily be applied to fully implicit models, while the unconstrained two-point upstream method is unstable for purely hyperbolic systems and is best suited for IMPES models. The use of higher order schemes in reservoir modelling has thus been extremely limited.
In order to remedy this situation, we derive a total variation diminishing (TVD) higher order scheme which can be applied to both fully implicit and IMPES Black-Oil models. We develop IMPES and fully implicit analogues of these schemes for use in standard Black Oil models and discuss their relationship to commonly used mobility weighting schemes (mid-point, single-point upstream, two-point upstream and single-point downstream).
The TVD mid-point scheme is a temporally first order version of the second order TVD flux limited Lax-Wendroff scheme. The TVD criterion ensures that oscillations which would have been produced by unconstrained second order schemes never arise. The unconditional stability of the fully implicit TVD mid-point scheme is guaranteed, since the limiter is evaluated along with the fully implicit flux terms. The IMPES implementation has a stability limit which is half that of the first order single-point upstream scheme.
Results using the IMPES and implicit TVD scheme in a modified commercial Black Oil code (VIP) are presented for three test problems. The first test, which is used to determine the order of the scheme, is the one dimensioned waterflooding of a slightly compressible oil reservoir (fully implicit formulation). The second test, for scheme accuracy, is the two dimensional water flooding of one-quarter of a 5 spot pattern (IMPES and fully implicit formulations) and the third test, again for accuracy, is the coning of water in a two dimensional radial (R-Z) coordinate system.
The results of the above examples are compared with standard first order calculations. In the examples presented, the TVD scheme produced more accurate results from models using one-seventh (and one-fourth) the number of blocks, resulting in a better than four-fold (and three-fold) saving of CRAY XMP CPU time.
The Grid Orientation Effect in Reservoir Simulation
Authors: Brand C. W. , Heinemann J. E. , Aziz K. 
Published: December 2007

Abstract
In the solution of adverse mobility ratio displacement problems by five-point difference schemes fluids appear to flow along grid lines. This results in solutions that depend on the orientation and size of the grid. Hence different results are obtained when, for example, the same one-quarter five-spot problem is solved by grids that are parallel and diagonal to the line joining the injector and the producer. This Grid Orientation Effect (GOE) is a result of coupling between the anisotropic numerical diffusion and the physical instability of the displacement front. In this paper, a linear stability analysis is applied to the finite difference equations to examine the interaction between numerical diffusion and the growth of numerical errors due to physical instability. The results show that in general the GOE cannot be overcome with grid refinement. For a certain range of parameters, however, first the GOE decreases under grid refinement, reaching a minimum, and then increases again on finer grids. A technique is provided for estimating reasonable block size for a given displacement problem.
An Efficient, Three-Dimensional, Fully Coupled Hydro-Thermo-Mechanical Simulator: FEHMS
Authors: Kelkar S. , Zyvoloski G. 
Published: December 2007

ABSTRACT
Hydro-thermo-mechanical effects in fractured rocks are important in many oilfield processes. Modeling these effects is made difficult by the fact that the governing equations are nonlinear and coupled, and the problems to be solved are three dimensional. In this paper we describe a numerical code developed for this purpose. The code is finite element based to allow for complicated geometries, and the time differencing is implicit, allowing for large time steps. The use of state-of-the-art equation solvers has resulted in a practical code. An example is presented to demonstrate the effects of matrix expansion, due to pore pressure and heating, on fracture opening due to fluid injection, and induced stress changes at a distant well bore.
A Fully Coupled, Fully Implicit Reservoir Simulator for Thermal and Other Complex Reservoir Processes
Authors: Mifflin R. T. , Watts J. W. , Weiser A. 
Published: December 2007

ABSTRACT
This paper describes a formulation for fully coupled, fully implicit reservoir simulation. This formulation is implemented as an option within a framework that already supports IMPES and sequential semi-implicit formulations. The resulting capability has received extensive use for the modeling of thermal processes, and has been used successfully to model coning and naturally fractured reservoirs as well.
This formulation differs from the most commonly-used approach in two ways.
Its equations are derived using the volume balance approach. This gives the resulting equations physical meaning that can be helpful in understanding the simulator's behavior. Also, it makes it possible to incorporate the resulting capability into an existing simulator that is based on the volume balance equations. In isothermal cases, it uses pressures and moles as the primary variables. When the thermal option is invoked, energy becomes the additional primary variable, rather than temperature. This avoids the complication of having to change variables when a phase disappears. Saturations and temperature are treated as functions of the primary variables.
A procedure based on the Newton-Raphson method is used to solve the resulting nonlinear equations. This procedure incorporates several techniques to enable or improve convergence in difficult circumstances.
The paper includes descriptions and discussions of the resulting simulator's performance in several examples.
Development of a Thermodynamically Consistent, Fully Implicit, Equation-of-State, Compositional Steamflood Simulator
Authors: Brantferger K. M. , Pope G. A. , Sepehrnoori K. 
Published: December 2007

ABSTRACT
A thermodynamically consistent, fully implicit, compositional, equation-of-state, steamflood simulator is described. The formulation uses a single set of primary variables-overall component mole numbers, total fluid enthalpy, and pressure-to linearize the finite difference forms of the component conservation equations, the energy conservation equation, and the pore volume constraint. These primary variables constitute a thermodynamically independent set; subsequently, they may be applied throughout the reservoir, supplanting the use of variable substitution. The resulting nonlinear system of equations is solved using the Newton-Raphson method to update the primary variables. At each iteration, local equilibrium is computed isenthalpically using a vectorized, Newton-type entropy maximization algorithm combined with a Gibbs stability test that yields the number of phases, the phase mole numbers, and temperature of the fluid mixture. This is the first time that such an approach has been taken within a steamflood simulator. Finally, examples are given that illustrate the importance of phase behavior on the residual oil saturation to steam.
Yield Points in Oilfield Cement Slurries
Authors: Clark P. E. , Sundaram L. , Balakrishnan M. 
Published: December 2007

Abstract
The determination of yield points in cement slurries is important in the overall description of slurry flow properties. Yield points affect both the start-up pressure after a temporary shut-down and void filling properties of cements. Values for the yield point are normally obtained by extrapolation of rotational or tube flow rheometer data. This technique is subject to both experimental and analytical errors.
Recently, a number of papers have described a more direct method of measuring yield points in slurries. A rotational viscometer equipped with a vane rather than a bob can be used to accurately measure yield points. The yield surface with the vane test fixture is in the fluid rather than at a fluid-solid interface as it is with a solid bob or a tube flow apparatus. Experiments with a vane fixture using a shear rate controlled rheometer can be subject to errors caused by wind-up of the torque spring. In this study a controlled stress rheometer was used to circumvent these problems.
Yield points for various oilfield cement slurries are presented. Data reflect the differences in additives, aging time and water content. The vane technique can be used to produce accurate and reproducible measurements of yield points in cements. Using a controlled stress instrument has a number of advantages in making these measurements.