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Pressure diffusion waves in porous media

Description: Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency.
Date: April 8, 2003
Creator: Silin, Dmitry; Korneev, Valeri & Goloshubin, Gennady
Partner: UNT Libraries Government Documents Department

Laboratory measurements of compressional and shear wave speeds through methane hydrate

Description: Simultaneous measurements of compressional and shear wave speeds through polycrystalline methane hydrate have been made. Methane hydrate, grown directly in a wave speed measurement chamber, was uniaxially compacted to a final porosity below 2%. At 277 K, the compacted material's compressional wave speed was 3650 {+-} 50 m/s. The shear wave speed, measured simultaneously, was 1890 {+-} 30 m/s. From these wave speed measurements, we derive Vp/Vs, Poisson's Ratio, bulk, shear and Young's moduli.
Date: October 25, 1999
Creator: Durham, W B; Waite, WF; Pinkston, J C; Stern, L A; Kirby, S H; Helgerud, M B et al.
Partner: UNT Libraries Government Documents Department

Geological Survey Investigations in the U12b.02 Tunnel, Nevada Test Site

Description: From introduction: The papers comprising the various parts of this report contain the preliminary results of the U. S. Geological Survey investigations in the U12b.02 tunnel at the Nevada Test Site.
Date: October 1958
Creator: Diment, William H.; Wilmarth, V. R.; McKeown, F. A.; Dickey, D. D.; Wilcox, R. E.; Botinelly, Theodore et al.
Partner: UNT Libraries Government Documents Department

Geological Survey Investigations in the U12b.01 Tunnel, Nevada Test Site

Description: From introduction: This report includes a brief description of the stratigraphy and structure, and data on petrology, mineralogy, and chemical and physical properties of the rocks that are exposed in the U12b.01 tunnel of the U12b (Rainier) tunnel system.
Date: March 1959
Creator: Diment, William H.; Wilmarth, V. R.; McKeown, F. A.; Dickey, D. D.; Botinelly, Theodore; Hinrichs, E. Neal. et al.
Partner: UNT Libraries Government Documents Department


Description: A new nonlinear thermo-mechanical model for heavily jointed rock masses is presented. The model uses correlation functions between the porosity and the basic rock properties such as elastic moduli, tensile and compressive strength. The model assumes that the media is isotropic and is characterized by two variable parameters: insipient porosity and in-situ-to-intact modulus ratio.
Date: March 8, 2007
Creator: Vorobiev, O
Partner: UNT Libraries Government Documents Department


Description: The porosity and diffusion length of concrete have been determined by measuring the time-dependent diffusion of radon through a thin slab of the material, One surface of the slab is exposed to a large, fixed radon concentration beginning at t=0. The radon that diffuses out of a portion of the opposite surface is collected during several contiguous time intervals. The total activity collected over a set of intervals beginning at t=0 and the steady-state flux of activity are used to calculate the porosity and diffusion length, As a test of these parameters, they are then used to predict the activity collected during other time intervals and for other sample thicknesses, Samples from two types of concrete were tested: one type yielded a porosity of 0.068 and a diffusion length of 12.6 cm; the respective values for the other were 0.32 and 16.9 cm. The predicted and experimental results agreed well, thereby verifying the assumption that concrete may be treated as a homogenous diffusion medium for radon.
Date: July 1, 1981
Creator: Zapalac, Geordie H.
Partner: UNT Libraries Government Documents Department

Estimates of frequency-dependent compressibility from a quasistatic double-porosity model

Description: Gassmann's relationship between the drained and undrained bulk modulus of a porous medium is often used to relate the dry bulk modulus to the saturated bulk modulus for elastic waves, because the compressibility of air is considered so high that the dry rock behaves in a drained fashion and the frequency of elastic waves is considered so high that the saturated rock behaves in an undrained fashion. The bulk modulus calculated from ultrasonic velocities, however, often does not match the Gassmann prediction. Mavko and Jizba examined how local flow effects and unequilibrated pore pressures can lead to greater stiffnesses. Their conceptual model consists of a distribution of porosities obtained from the strain-versus-confining-pressure behavior. Stiff pores that close at higher confining pressures are considered to remain undrained (unrelaxed) while soft pores drain even for high-frequency stress changes. If the pore shape distribution is bimodal, then the rock approximately satisfies the assumptions of a double-porosity, poroelastic material. Berryman and Wang [1995] established linear constitutive equations and identified four different time scales of ow behavior: (1) totally drained, (2) soft pores are drained but stiff pores are undrained, (3) soft and stiff pores are locally equilibrated, but undrained beyond the grain scale, and (4) both soft and stiff pores are undrained. The relative magnitudes of the four associated bulk moduli will be examined for all four moduli and illustrated for several sandstones.
Date: September 16, 1998
Creator: Berryman, J. G. & Wang, H. F.
Partner: UNT Libraries Government Documents Department

Strategies for reservoir characterization and identification of incremental recovery opportunities in mature reservoirs in Frio Fluvial-Deltaic sandstones, south Texas: An example from Rincon Field, Starr County. Topical report

Description: Fluvial-deltaic sandstone reservoirs in the United States are being abandoned at high rates, yet they still contain more than 34 billion barrels of unrecovered oil. The mature Oligocene-age fluvial-deltaic reservoirs of the Frio Formation along the Vicksburg Fault Zone in South Texas are typical of this class in that, after more than three decades of production, they still contain 61 percent of the original mobile oil in place, or 1.6 billion barrels. This resource represents a tremendous target for advanced reservoir characterization studies that integrate geological and engineering analysis to locate untapped and incompletely drained reservoir compartments isolated by stratigraphic heterogeneities. The D and E reservoir intervals of Rincon field, Starr County, South Texas, were selected for detailed study to demonstrate the ability of advanced characterization techniques to identify reservoir compartmentalization and locate specific infield reserve-growth opportunities. Reservoir architecture, determined through high-frequency genetic stratigraphy and facies analysis, was integrated with production history and facies-based petrophysical analysis of individual flow units to identify recompletion and geologically targeted infill drilling opportunities. Estimates of original oil in place versus cumulative production in D and E reservoirs suggest that potential reserve growth exceeds 4.5 million barrels. Comparison of reservoir architecture and the distribution of completions in each flow unit indicates a large number of reserve-growth opportunities. Potential reserves can be assigned to each opportunity by constructing an Sooh map of remaining mobile oil, which is the difference between original oil in place and the volumes drained by past completions.
Date: November 1, 1995
Creator: McRae, L.; Holtz, M. & Hentz, T.
Partner: UNT Libraries Government Documents Department

The minimum pore size obtainable in a silica gel during drying

Description: The pore size r{sub p} in a gel is determined by the extent of shrinkage of the gel network during drying. Shrinkage is driven by the collapse of the gel network in response to the capillary pressure P{sub c} exerted by the pore fluid. The extent of shrinkage depends on the balance between the capillary pressure P{sub c} in the pore fluid and the bulk modulus K{sub p} of the gel. The hydraulic pore radius, r{sub H} = 2V{sub p}/S{sub a}, where V{sub p} is the pore volume and S{sub a} is the apparent N{sub 2} BET surface area, is often used to characterize the pore size of a gel. A series of acid catalyzed silica gels dried in pore fluids with different {gamma}{sub lv}, showed that there is a limit to the minimum apparent r{sub H} obtainable in a gel, and when the volume fraction of porosity {phi} {le} 0.37, r{sub H} becomes constant and {approximately}0.8 nm. In contrast, experimental data show that the true pore size r{sub p} of gels continues to decrease when {phi} {le} 0.37. Analysis of their adsorption isotherms show that while r{sub H} apparently stays constant: (a) the BET C constant continues to increase, (b) the width and average of their pore size distributions continue to decrease, and (c) as shrinkage continues the gels eventually become non-porous to N{sub 2} at 77K but are still porous to CO{sub 2} at 273K. This paper reviews these results and addresses micropore formation in silica gels with the goal of determining how P{sub c} influences the final r{sub p}, and why r{sub p} and r{sub H} diverge when {phi} {le} 0.37.
Date: December 1994
Creator: Wallace, S.; Brinker, C. J. & Smith, D. M.
Partner: UNT Libraries Government Documents Department

Structural Evolution of Carbon During Oxidation

Description: The examination of the structural evolution of carbon during oxidation has proven to be of scientific interest. Early modeling work of fluidized bed combustion showed that most of the reactions of interest occurs iOn the micropores, and this work has concentrated on these pores. This work has concentrated on evolution of macroporosity and rnicroporosity of carbons during kinetic controlled oxidation using SAXS, C02 and TEM analysis. Simple studies of fluidized bed combustion of coal chars has shown that many of the events considered fragmentation events previously may in fact be "hidden" or nonaccessible porosity. This makes the study of the microporous combustion characteristics of carbon even more important. The generation of a combustion resistant grid, coupled with measurements of the SAXS and C02 surface areas, fractal analysis and TEM studies has confined that soot particles shrink during their oxidation, as previously suspected. However, this shrinkage results in an overall change in structure. This structure becomes, on a radial basis, much more ordered near the edges, while the center itself becomes transparent to the TEM beam, implying a total lack of structure in this region. Although complex, this carbon structure is probably burning as to keep the density of the soot particles nearly the same. The TEM techniques developed for examination of soots has also been applied to Spherocarb. The Spherocarb during oxidation also increases its ordering,. This ordering, by present theories, would imply that the reactivity would go. However, the reactivity goes up, implying that structure of carbon is secondary in importance to catalytic effects.
Date: October 28, 1998
Creator: Sarofim, Adel F. & Kandas, Angelo
Partner: UNT Libraries Government Documents Department

Integrated Outcrop and Subsurface Studies of the Interwell Environment of Carbonate Reservoirs: Clear Fork (Leonaradian Age) Reservoirs, West Texas and New Mexico

Description: The objective of this report is to characterize fracture porosity and distribution in the Wasson Clear Fork reservoir and to determine the effects of fractures on well performance. The approach is to measure fracture attributes in an analog outcrop, to develop models of fracture spacing and aperture, and to apply this information to the South Wasson Clear Fork reservoir.
Date: May 8, 2001
Creator: Lucia, F. Jerry & Laubach, Stephen E.
Partner: UNT Libraries Government Documents Department


Description: A powder metallurgical approach is utilized to prepare grain oriented Laves phase compounds of Tb{sub x}Dy{sub 1-x}Fe{sub 2}. The magnetostrains observed in the oriented compounds, though containing {approx}20% porosity as presently prepared, are far superior to those of arc cast and highly dense liquid phase sintered materials. Also, it is shown that the alignment achieved is strongly dependent on the Tb/Dy ratio.
Date: October 1, 1977
Creator: Malekzadeh, M. & Pickus, M.R.
Partner: UNT Libraries Government Documents Department

Importance of Deviatoric Stress in Modeling Void Growth in Ductile Fracture

Description: In this paper, the authors extend an upper bound result of Cocks [1989] to obtain a formula for porosity growth in ductile metals. Pressure and deviatoric stress are included. The matrix plasticity model involves the plastic strain rate as a power of the deviatoric stress, with a yield stress. The results show that the deviatoric stress cannot be neglected in calculating the porosity growth, even for high triaxialities.
Date: January 1, 1999
Creator: Tonks, D.L.; Zurek, A.K.; Thissell, W.R.; Rivera, J.M. & Hixson, R.S.
Partner: UNT Libraries Government Documents Department

New perspectives on the fracture of Nicalon fibers

Description: Experimental studies have been conducted to examine the strength and fracture behavior of monofiliment Nicalon{sup 3} SiC fibers ranging in diameter from 8 to 22 {mu}m. The effects of varying fiber diameter, flaw location and flaw population on the tensile behavior of individual fibers were investigated using fractography. Results indicate that variations in fiber diameter influence the apparent fiber fracture toughness K{sub 1c}, with higher K{sub 1c} values observed for decreasing fiber diameters. Observations also suggest that the location of the critical flaw may play a role in the fracture of Nicalon fibers. In addition to surface flaws, three distinct internal flaw populations are seen to cause fracture in Nicalon fibers.
Date: November 1, 1997
Creator: Taylor, S.T.; Lowe, T.C. & Butt, D.P.
Partner: UNT Libraries Government Documents Department

Evaluating Transmissivity Estimates from Well Hydrographs in Karst Aquifers

Description: Hydrograph recessions from rainfall events have previously been analyzed for discharge at springs and streams; however, relatively little quantitative research has been conducted with regard to hydrograph analysis of recessions from monitoring wells screened in karst aquifers. In previous work a quantitative hydrography analysis technique has been proposed born which matrix transmissivity (i.e., transmissivity of intergranular porosity) and specific yields of matrix, fracture, and conduit components of the aquifer may be determined from well hydrography. The technique has yielded realistic results at three sites tested by the authors thus far (Y-12, Oak Ridge, TN; Crane, IN, and Ft. Campbell, KY). Observed field data, as well as theoretical considerations, show that karst well hydrography are valid indicators of hydraulic properties of the associated karst aquifers. Results show matrix transmissivity (T) values to be in good agreement with values calculated using more traditional parameter estimation techniques such as aquifer pumping tests and slug tests in matrix dominated wells. While the hydrograph analysis technique shows promise for obtaining reliable estimates of karst aquifer T with a simple, relatively inexpensive and passive method, the utility of the technique is limited in its application depending on site-specific hydrologic conditions, which include shallow, submerged conduit systems located in areas with sufficient rainfall for water levels to respond to precipitation events.
Date: July 1, 1999
Creator: Powers, J.g. & Shevenell, l
Partner: UNT Libraries Government Documents Department

Stress Isotherms of Porous Thin Materials: Theoretical Predictitions From a Nonlocal Density Functional Theory

Description: Recent beam bending (BB) experiments of microporous t31rns with very small pores have shown that the fluid confined in these pores exhibits monotonic compressive stresses as the relative pressure is varied from vacuum to saturation (relative vapor pressure, p/p. = 1). The variation of the stress near saturation is found to be linear in hz(p) and given by the saturated liquid density to within 20%. Capillary condensed fluids are traditionally described by the Laplace-Kelvin (LK) theory. LK theory correctly predicts the slope of the stress near saturation to be pl, but also predicts that the stress should be zero at saturation and tensile between saturation aud the capillary transition pressure. Hence LK theory does not capture the monotonic compressive stress observed in BB experiments. This report describes the results of density functional theory calculations for a simple fluid continued to a slit pore network. We show how the presence of even a small amount of polydispersity in pore size leads to both a monotonic compressive stress as well as the observed LK slope.
Date: November 11, 1998
Creator: Frink, L.J.D. & van Swol, F.
Partner: UNT Libraries Government Documents Department

Understanding the Relationship Between Filling Pattern and Part Quality in Die Casting

Description: The overall objective of this research project was to investigate phenomena involved in the filling of die cavities with molten alloy in the cold chamber die-casting process. It has long been recognized that the filling pattern of molten metal entering a die cavity influences the quality of die-cast parts. Filling pattern may be described as the progression of molten metal filling the die cavity geometry as a function of time. The location, size and geometric configuration of points of metal entry (gates), as well as the geometry of the casting cavity itself, have great influence on filling patterns. Knowledge of the anticipated filling patterns in die-castings is important for designers. Locating gates to avoid undesirable flow patterns that may entrap air in the casting is critical to casting quality - as locating vents to allow air to escape from the cavity (last places to fill). Casting quality attributes that are commonly flow related are non-fills, poor surface finish, internal porosity due to trapped air, cold shuts, cold laps, flow lines, casting skin delamination (flaking), and blistering during thermal treatment.
Date: March 15, 2004
Creator: Brevick, Jerald & Miller, R. Allen
Partner: UNT Libraries Government Documents Department


Description: Excellent progress has been made on all project objectives and goals. All tasks have been completed in the Phase 1 study area, the initial area of project focus. Primary elements of this work include the following: The stratigraphic architecture has been established through correlation of wireline logs guided by core and outcrop studies of facies and cyclicity. A porosity model has been developed that creates a basis for calculation of porosity for wells in the study area. Rock fabrics have been defined by sampling, analysis, and description of cores and used to create transforms for calculating permeability and oil saturation from porosity data. Finally, a preliminary 3-D model has been constructed that incorporates stratigraphic architecture, rock-fabric data, and petrophysical data. Reservoir volumetrics calculated from the model show that a very large fraction of the original oil in place remains.
Date: January 1, 2003
Creator: Ruppel, Stephen C.
Partner: UNT Libraries Government Documents Department