bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Diffusion on Dispersion
Authors: Jha Raman K. , Bryant Steven L. , Lake Larry W. 
Published: September 2008

AbstractWe study dispersion in porous media by tracking movement of a swarm of solute particles through a physically representative network model. We developed deterministic rules to trace paths of solute particles through the network. These rules yield flow streamlines through the network comparable to those obtained from a full solution of Stokes’ equation. In the absence of diffusion the paths of all solute particles are completely determined and reversible. We track the movement of solute particles on these paths to investigate dispersion caused by purely convective spreading at the pore scale. Then we superimpose diffusion and study its influence on dispersion. In this way we obtain for the first time an unequivocal assessment of the roles of convective spreading and diffusion in hydrodynamic dispersion through porous media. Alternative particle tracking algorithms that use a probabilistic choice of an out-flowing throat at a pore fail to quantify convective spreading accurately.For Fickian behavior of dispersion it is essential that all solute particles encounter a wide range of independent (and identically distributed) velocities. If plug flow occurs in the pore throats a solute particle can encounter a wide range of independent velocities because of velocity differences in pore throats and randomness of pore structure. Plug flow leads to a purely convective spreading that is asymptotically Fickian. Diffusion superimposed on plug flow acts independently of convective spreading causing dispersion to be simply the sum of convective spreading and diffusion. In plug flow hydrodynamic dispersion varies linearly with the pore-scale Peclet number.For a more realistic parabolic velocity profile in pore throats particles near the solid surface of the medium do not have independent velocities. Now purely convective spreading is non-Fickian. When diffusion is non-zero, solute particles can move away from the low velocity region near the solid surface into the main flow stream and subsequently dispersion again becomes asymptotically Fickian. Now dispersion is the result of an interaction between convection and diffusion and it results in a weak non-linear dependence of dispersion on Peclet number. The dispersion coefficients predicted by particle tracking through the network are in excellent agreement with the literature experimental data.We conclude that the essential phenomena giving rise to hydrodynamic dispersion observed in porous media are (i) stream splitting of the solute front at every pore, thus causing independence of particle velocities purely by convection, (ii) a velocity gradient within throats and (iii) diffusion. Taylor's dispersion in a capillary tube accounts for only the second and third of these phenomena, yielding a quadratic dependence of dispersion on Peclet number. Plug flow in the bonds of a physically representative network accounts for the only the first and third phenomena, resulting in a linear dependence of dispersion upon Peclet number.
Rewarding and Reducing Risk: Harnessing the Potential of Entrepreneurs in the Oil & Gas Industry
Authors: Preston Robert , Leggett Nigel 
Published: September 2008

Abstract
This Paper examines the financial and industry mindset barriers which exist at either end of the research and development (R&D) process for entrepreneurial businesses commercialising new technology for the Oil & Gas services (O&G) sector.
It examines the core business skills entrepreneurs require to secure adoption of their technology in a competitive market and whether respondents felt they possessed these skills – particularly the ‘human’ factor; industry contacts and relationships, communication skills and product marketing.
Using a research model developed by Professor Shailendra Vyakarnam, Director Cambridge Centre for Entrepreneurial Learning, the report examines the industry and compares the funding climate to comparative sectors where entrepreneurial innovation is crucial in order to build a valuable business which will ultimately attract potential acquirers of the company or its technology.
Fluid-Phase Behaviour for a Miscible-Gas-Injection EOR Project in a Giant Offshore Oil Field With Large Compositional Variations
Authors: Lindeloff N. , Mogensen K. , van Lingen P. , Do S. H. , Frank S. , Noman R. 
Published: September 2008

Abstract
Gas injection as an EOR method is being considered for the giant Al Shaheen field, located offshore Qatar. The field is characterized by large lateral variations in fluid properties across the field. The oil gravity ranges from 16 to 38 °API and significant variations in initial GOR and saturation pressure are observed. The field is developed with horizontal wells with up to 35,000 ft long reservoir sections. The oil gravity may vary considerably along a horizontal well, which needs to be considered when evaluating further field development options involving miscible as well as immiscible gas injection.
An extensive experimental program aimed at establishing a model for the miscibility behavior for this complex fluid system is described. The work resulted in the development of an equation of state (EOS) model capturing the miscibility behavior across the range of API gravities, as well as a set of black oil correlations consistent with the EOS.
A method for initializing compositional reservoir simulations with the developed EOS based on API, GOR and saturation pressure maps of the field was developed. This methodology allowed a finely discretized compositional variation to be represented in the compositional simulation models giving an accurate and detailed fluid phase behavior description.
Compressible Streamline-Based Simulation With Changes in Oil Composition
Authors: Beraldo V. T. , Blunt M. J. , Schiozer D. J. 
Published: September 2008

Abstract
There are several oil fields offshore Brazil with horizontal oil density variations. API tracking, that is available in some commercial finite difference simulators, can deal with such cases by allowing definition of an initial oil gravity distribution and tracking variations of oil density, due to the movement of oil.
Streamline-based simulators can be much faster than conventional finite difference simulators when applied to large and heterogeneous models. However, this approach is most accurate and efficient when it is assumed that the rock and fluids are incompressible. In previous work (Beraldo et al, 2007), we presented an incompressible formulation for streamline simulation with an API Tracking option using two components in the oleic phase.
This paper presents a compressible formulation for streamlines that also considers API tracking. It extends the work of Cheng et al. (2006) and Osako and Datta-Gupta (2007) by consistently accounting for flux of mass and volume along streamlines. We describe how mass and volume can be mapped between the underlying grid and streamlines to minimize mass balance errors and how consideration of cumulative volume in a streamline can substitute for time-of-flight.
The method was implemented in a three-dimensional two-phase streamline-based simulator. Tests based on a Brazilian oilfield model and on the SPE10th Comparative Case demonstrate that the implementation can reproduce the results of a conventional simulator, while being substantially faster for finely-resolved models, even when compressibility is significant.
An Analysis of Noise Characteristics of Drill Bits
Authors: Gradl Christian , Eustes Alfred W. , Thonhauser Gerhard 
Published: September 2008

Abstract
There have been papers that analyse the relationship between drill bit design and its vibrational characteristics. These papers typically are based on the analysis of three-axis down-hole vibration sensors located near the bit. 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 analyse the resulting noise for basic information on the bit.
The data were gathered at the Colorado School of Mines in Golden, Colorado. The noise of a PDC, roller cone, and diamond bit were recorded under various operational parameters using microphones and a 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.
Summarizing the results of the analysis of the roller cone bit, the PDC, and the natural diamond bit, major differences in their 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 of cutting elements and frequency peaks on a plot of amplitude vs. 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 a strong on the diamond bit data. The conclusion is that bit characteristics can be determined using only acoustical data (ie. the noise of a bit). Potential applications of this research include detecting and diagnosing bit problems (e.g. broken teeth, bit balling) in real time using acoustic data.
Improving Reservoir Characterization Using Accurate Flow-Rate History
Authors: Pinilla E. J. , Pardo C. H. , Warlick L. M. , Al-Shobaili Y. M. , Aftab M. N. , Khan A. , Rahman N. M. A. 
Published: September 2008

Abstract
Well testing is one of the most effective means to characterize hydrocarbon reservoirs under dynamic conditions. Such characterization of reservoirs is as accurate as the data used for interpretation. It is, therefore, essential to have accurate measurements of both rates and pressures due to their complementary nature. Although pressure measurements are accurate, one needs to pay more attention to the rate measurements, especially during the early stages of exploration. Accurate measurements of gas and liquid flow rates using a separator are very difficult because of poor separation among the three phases when the flowing oil is heavy and viscous. This condition gets even worse in situations like low gas rates, low density contrasts among liquids, contamination of the different effluents after separation, and well instabilities leading to carry-over or carry-under.
Multiphase metering based on a dual-energy Venturi technology enables simultaneous, accurate rate measurements of oil, water and gas phases produced from development, exploration or appraisal wells, while the downhole gauges measure the pressures.
This paper presents comprehensive results from field tests conducted with multiphase meters in carbonate reservoirs producing Arabian heavy oil. These tests were conducted with production logging tools enabling characterization of laminated layers. Complete analyses of downhole gauge data are presented to demonstrate how the characterization of investigated formations improves with accurate rate measurements. It is also shown that if the rate measurements are not rigorous, it might lead to a misleading interpretation of the acquired pressure data.
The Methods for Determining the Viability of Electronic Textbooks and Their Hardware for Use in the University Environment: The Trips, Tricks, and Traps for Their Selection
Authors: Platt F. M. , Hausman L. A. 
Published: September 2008

Abstract
Technology for teaching has changed dramatically over the years from pen and paper to typed pages to the latest technology, electronic print. This paper investigates the potential for their use in the University environment. Part of this problem is the determination of what is available, where to find it and what method to display it for the student to use. A final item of this list is cost for the application and hardware. Is it comparable to hard copy paper books?
Electronic books have been in the market for several years but their usability in the classroom has been limited. Books must be downloaded to some type of device for the student to access. Until the reduction in hardware cost the primary application or delivery device was the desktop computer. With the reduction in cost of laptops this becomes more usable and with the new electronic readers this becomes even more viable. Now the cost of the reader is comparable to the savings in using electronic books.
This work will investigate the viability of electronic books for Petroleum Engineering. We will include an analysis of what is available, the functionality of the readers as well as an analysis of the cost of the application. A sidebar to this task is the ability for the engineer to carry his/her library with them into the field. Something unheard of ten years ago. An engineer on a project will not have to go back to the office to find a reference for their project, it will either be on his laptop or on an electronic reader.
Analysis of this topic would not be complete without discussion of media format. Will a format used today be available in ten years? Will a book bought today be useable on hardware yet to be created? These are questions that will be addressed in this paper. The primary conclusion of this paper is that electronic books are a viable method but proper care must be used to determine the optimum solution. The cost of replacement in the event of an incorrect selection could be disastrous.
Valuing Oil and Gas Options by Least-Squares Monte Carlo Simulation
Authors: Willigers B. J. A. , Bratvold R. B. 
Published: September 2008

Abstract
Least-Squares Monte Carlo simulation (LSM) is a promising new technique for valuing real options that has received little or no attention in the oil and gas industry. In this paper, we will demonstrate how LSM can handle more realistic valuation situations including the ability to (i) handle more realistic (probabilistic) price models and (ii) deal with multiple, possibly correlated, uncertain variables.
The LSM method is applied here to an economics problem faced by many operators: What is the value of a gas field given the decision to trade the gas on the spot market as opposed to selling the gas through a long-term supply contract? A company that chooses to trade gas can decide when and how much to produce and can profit from changing market conditions, as by increasing production during a high-price environment.
Three uncertainties have been modeled: the gas price, the operational costs, and the rate of production decline. Increasing profitability associated with rising hydrocarbon prices is typically partially offset by increasing expenditures. Hence the costs have been correlated with the gas price. The expectation of the remaining reserves is continuously adjusted on the basis of the performance of the field. The latter is simulated by stochastically modeling the rate of production decline.
The paper shows that a gas field that can be produced and abandoned at will has large value of flexibility. The Net Present Value of such an asset will underestimate the true economic value. A further benefit of using the real option valuation approach discussed here is that the valuation procedure produces a strategy map showing actions within the project, not just numbers.
Thermally-Enhanced Evaporation Process in Fractured Reservoirs— A Pore-Network Study
Authors: Tajer Ehsan S. , Yortsos Yannis C. 
Published: September 2008

Abstract
We study evaporation processes in fractured reservoirs under thermally enhanced conditions using pore-network models. The emphasis is on understanding evaporation phenomena and the combined effects of capillarity and viscous forces as are modified by the presence of thermal gradients and an applied heat flux. The temperature dependence of equilibrium vapor concentration and surface tension and macroscopic corner films are included.
The phase distribution evolution, liquid saturation, film flow and recovery rates are obtained as functions of dimensionless parameters in the two cases of positive and negative temperature gradients. The results are obtained without the use of empirical or ad hoc coefficients and parameters.
Strong evaporation effects under thermal conditions, associated with the variation of equilibrium concentrations, are clearly shown. The influence of surface tension variation induced by thermal gradients leads to destabilizing or stabilizing invasion percolation fronts, depending on the direction of the thermal gradient.
The paper finds application to the recovery of volatile oils from fractured or heterogeneous reservoirs by thermal processes, such as steam injection.
Using Industry Standards as a Way to Predict Sand Performance and Approve Sand Deposits: Is there a Catch 22?
Authors: Brannon H. D. , Stephenson C. J. , Freeman E. R. , Anschutz D. A. , Renkes J. J. , Rickards A. R. 
Published: September 2008

Abstract
The sands employed as fracturing proppant have been historically qualified for that purpose based upon their ability to meet quality standards described by the American Petroleum Institute (API, 1995) and more recently, by the International Organization for Standardization (ISO, 2006). Notable products meeting those standards include white sands from the Ottawa deposits in the north central United States, and the so-called brown sands from deposits in central or the "heart" of Texas. Until recent times, these "quality" sand deposits provided sufficient supplies for the ongoing needs. However, the unprecedented surge of hydraulic fracturing activities over the past few years has resulted in demand outpacing the supply for sands that meet these requirements.
Consequently, many ‘new’ sand deposits are being evaluated for use in fracturing applications, but unfortunately, a great many of those when subjected to API / ISO standards fail to make the grade in one area or another. Interestingly, it is commonly similar criteria which are being failed including acid solubility, sphericity & roundness, crush strength, and particle distribution. Thus, one is given cause to question the relevance of some testing practices on ‘real world’ performance of sand in a fracturing treatment.
It is this point which illustrates a "Catch 22". A sand can pass industry standards as a quality proppant, but it may not necessarily meet the performance, or conductivity, requirements of a reservoir. Yet, as this study demonstrates, a sand source that fails some of the standard testing parameters might still meet the flow capacity needs of a reservoir.
One can better understand the role that industry standards play in predicting sand performance and in approving sand deposits through closer examination. So, first, a discussion of some of the individual quality standards and their influence will be shared. Secondly, empirical data will demonstrate relative impact on sand performance, via conductivity, when one or more of qualifying parameters fails to pass. Lastly, guidance will be provided for the use of sands and other proppants, which although technically are unacceptable per industry standards, may be perfectly acceptable as ‘fit-for-purpose’ proppants in at least some segment of the fracturing market.
Study of New Solutions for Acid-Resistant Cements
Authors: Lécolier E. , Rivereau A. , Ferrer N. , Audibert A. , Longaygue X 
Published: September 2008

Abstract
In the near future, the production of oilfields with high contents of associated sour gases will increase. Research on technologies to produce such fields are therefore of utmost importance. Due to the presence of corrosive gas, special attention has to be paid to the design of well materials (casing, cementing materials). However, published data on degradation mechanisms of cement-based materials exposed to H2S environments are very scarce. When placed in contact with acid fluid, portland cement will dissolve and become, at some time, fully degraded. In this case, the zonal isolation will be no more effective. New solutions are required to ensure long-term integrity of cementing materials. One potential solution is to incorporate chemicals in the cementitious matrix. The key idea is to incorporate additives that react preferentially with H2S and not with hydrated phases of the cement. The goal of this work was to assess this solution.
The paper is dealing with cement formulations that incorporate mineral admixtures. These mineral admixtures have been chosen because of their high chemical affinity with hydrogen sulphide. We first give properties (density, compressive strength, rheological behaviour) of the novel formulations. Then we describe the static ageing tests performed in H2S-saturated brine at 120°C and 15 MPa. By combining different analytical techniques, the chemical evolution of the new formulations has been investigated.
The results are dependent on the nature of the reactive mineral admixture. We show that, in some particular case, the incorporation of specific mineral admixtures leads to a strong damaging effect for the cement matrix. Consequently, for the design of H2S-resistant cement, these specific mineral admixtures should be discarded. The proposed solution (addition of reactive chemicals) is promising but requires more investigation in order to carefully control the reactivity of the different chemical species.
Determination of In-situ Two-Phase Flow Properties through Downhole Fluid Movement Monitoring
Authors: Kuchuk Fikri , Zhan Lang , Ma S. Mark , Al-Shahri Ali M. , Ramakrishnan T. S. , Altundas Bilgin , Zeybek Murat , de Loubens Romain , Chugunov Nikita 
Published: September 2008

AbstractIn this paper, we present a novel method for in situ estimation of two-phase transport properties of porous media using time-lapse resistivity, pressure, and flow rate data from a permanent downhole Electrode Resistivity Array (ERA) and pressure, and a production logging tool. The primary objective of this Fluid Movement Monitoring (FMM) setup and experiment is to provide in-situ measurements required to determine multiphase flow properties, such as relative permeabilities and capillary pressures. Continuous monitoring of oil displacement by injected water in all the permeable zones was conducted in a carbonate reservoir in Saudi Arabia.The field experiment was divided into two stages: 1) Selection of the well location, coring and logging, experimental setup and completion designs, cleanup, production profiles, pressure transient buildup tests, water injection and subsequent production of all injected water, and collection of all relevant data that include time-lapse pressure, production and injection profiles, and resistivity; and 2) Interpretation of all the data acquired from different sources, development of algorithms/software to compute the movement of the injected fluid through the reservoir, and the inversion of multi-source and multi-physics measurements. This monitoring experiment was achieved through an integrated interpretation of different data sets such as transient drawdown/injection and drawdown/buildup tests, 3D deep resistivity, production and injection profiles, openhole log, and core measurements. This approach is new to the industry and the first field experiment for direct in situ determination of two-phase flow properties. The key outcome of this field experiment is a full verification of the permanent downhole resistivity array and pressure sensor experimental setup for estimating in-situ layer relative permeabilities and capillary pressure and monitoring water movement inside the formation. This allowed multiphase characterization of the formation around the measurement well to a radial depth of tens of meters.