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Direct Reservoir Parameter Estimation Using Joint Inversion ofMarine Seismic AVA&CSEM Data

Description: A new joint inversion algorithm to directly estimate reservoir parameters is described. This algorithm combines seismic amplitude versus angle (AVA) and marine controlled source electromagnetic (CSEM) data. The rock-properties model needed to link the geophysical parameters to the reservoir parameters is described. Errors in the rock-properties model parameters, measured in percent, introduce errors of comparable size in the joint inversion reservoir parameter estimates. Tests of the concept on synthetic one-dimensional models demonstrate improved fluid saturation and porosity estimates for joint AVA-CSEM data inversion (compared to AVA or CSEM inversion alone). Comparing inversions of AVA, CSEM, and joint AVA-CSEM data over the North Sea Troll field, at a location with well control, shows that the joint inversion produces estimated gas saturation, oil saturation and porosity that is closest (as measured by the RMS difference, L1 norm of the difference, and net over the interval) to the logged values whereas CSEM inversion provides the closest estimates of water saturation.
Date: January 12, 2005
Creator: Hoversten, G. Michael; Cassassuce, Florence; Gasperikova, Erika; Newman, Gregory A.; Rubin, Yoram; Zhangshuan, Hou et al.
Partner: UNT Libraries Government Documents Department

Seismic imaging of reservoir flow properties: Time-lapse pressurechanges

Description: Time-lapse fluid pressure and saturation estimates are sensitive to reservoir flow properties such as permeability. In fact, given time-lapse estimates of pressure and saturation changes, one may define a linear partial differential equation for permeability variations within the reservoir. The resulting linear inverse problem can be solved quite efficiently using sparse matrix techniques. An application to a set of crosswell saturation and pressure estimates from a CO{sub 2} flood at the Lost Hills field in California demonstrates the utility of this approach. From the crosswell estimates detailed estimates of reservoir permeability are produced. The resulting permeability estimates agree with a permeability log in an adjacent well and are in accordance with water and CO{sub 2} saturation changes in the interwell region.
Date: April 8, 2003
Creator: Vasco, Don W.
Partner: UNT Libraries Government Documents Department

Numerical studies of enthalpy and CO2 transients in two-phasewells

Description: Numerical studies of enthalpy and CO2 transients for wellscompleted in composite reservoir systems are carried out. Both constantrate and constant pressure production are considered. The results showthat relatively small variations in hydrologic parameters and vaporsaturation can have large effects on the enthalpy and CO2 content of theproduced fluids. Field data are presented that illustrate the theoreticalresults obtained.
Date: April 1, 1984
Creator: Bodvarsson, Gudmundur S.
Partner: UNT Libraries Government Documents Department

Aza Cope Rearrangement of Propargyl Enammonium Cations Catalyzed By a Self-Assembled `Nanozyme

Description: The tetrahedral [Ga{sub 4}L{sub 6}]{sup 12-} assembly (L = N,N-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene) encapsulates a variety of cations, including propargyl enammonium cations capable of undergoing the aza Cope rearrangement. For propargyl enammonium substrates that are encapsulated in the [Ga{sub 4}L{sub 6}]{sup 12-} assembly, rate accelerations of up to 184 are observed when compared to the background reaction. After rearrangement, the product iminium ion is released into solution and hydrolyzed allowing for catalytic turnover. The activation parameters for the catalyzed and uncatalyzed reaction were determined, revealing that a lowered entropy of activation is responsible for the observed rate enhancements. The catalyzed reaction exhibits saturation kinetics; the rate data obey the Michaelis-Menten model of enzyme kinetics, and competitive inhibition using a non-reactive guest has been demonstrated.
Date: February 27, 2008
Creator: Hastings, Courntey J.; Fiedler, Dorothea; Bergman, Robert G. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

WATEQF: A FORTRAN IV Version of WATEQ, a Computer Program for Calculating Chemical Equilibrium of Natural Waters

Description: Abstract: WATEQF is a FORTRAN IV computer program that models the thermodynamic speciation of inorganic ions and complex species in solution for a given water analysis. The original version (WATEQ) was written in 1973 by A. H. Truesdell and B. F. Jones in Programming Language/one (PL/1). With but a few exceptions, the thermochemical data, speciation, activity coefficients, and general calculation procedure of WATEQF is identical to the PL/1 version. This report notes the differences between WATEQF and WATEQ, demonstrates how to set up the input data to execute WATEQF, provides a test case for comparison, and makes available a listing of WATEQF.
Date: September 1976
Creator: Plummer, L. Niel; Jones, Blair F, & Truesdell, Alfred H.
Partner: UNT Libraries Government Documents Department

Examining the Shade/flood Tolerance Tradeoff Hypothesis in Bottomland Herbs Through Field Study and Experimentation

Description: While there is growing evidence that shade/flood tolerance tradeoffs may be important in distributions of bottomland hardwood trees and indications that they should apply to herbs, no studies have definitively explored this possibility. Four years of field data following historic flooding were supplemented with a greenhouse experiment designed to identify interactions congruent with tradeoffs. Fifteen bottomland species were grown in two levels of water availability and three levels of shade over 10 weeks. Results indicate responses of Fimbristylis vahlii and Ammannia robusta are consistent with tradeoffs. Modification of classical allometric responses to shade by substrate saturation indicates a potential mechanism for the tradeoff in A. robusta. Responses indicating potential for increased susceptibility to physical flooding disturbance are also discussed.
Date: May 2012
Creator: Sloop, Jordan
Partner: UNT Libraries

A sampling-based Bayesian model for gas saturation estimationusing seismic AVA and marine CSEM data

Description: We develop a sampling-based Bayesian model to jointly invertseismic amplitude versus angles (AVA) and marine controlled-sourceelectromagnetic (CSEM) data for layered reservoir models. The porosityand fluid saturation in each layer of the reservoir, the seismic P- andS-wave velocity and density in the layers below and above the reservoir,and the electrical conductivity of the overburden are considered asrandom variables. Pre-stack seismic AVA data in a selected time windowand real and quadrature components of the recorded electrical field areconsidered as data. We use Markov chain Monte Carlo (MCMC) samplingmethods to obtain a large number of samples from the joint posteriordistribution function. Using those samples, we obtain not only estimatesof each unknown variable, but also its uncertainty information. Thedeveloped method is applied to both synthetic and field data to explorethe combined use of seismic AVA and EM data for gas saturationestimation. Results show that the developed method is effective for jointinversion, and the incorporation of CSEM data reduces uncertainty influid saturation estimation, when compared to results from inversion ofAVA data only.
Date: April 4, 2006
Creator: Chen, Jinsong; Hoversten, Michael; Vasco, Don; Rubin, Yoram & Hou,Zhangshuan
Partner: UNT Libraries Government Documents Department

Crosswell seismic and electromagnetic monitoring of CO2sequestration

Description: The quantitative estimation of changes in water saturation (S{sub W}) and effective pressure (P), in terms of changes in compressional and shear impedance, is becoming routine in the interpretations of time-lapse surface seismic data. However, when the number of reservoir constituents increases to include in situ gas and injected CO{sub 2}, there are too many parameters to be determined from seismic velocities or impedances alone. In such situations, the incorporation of electromagnetic (EM) images showing the change in electrical conductivity ({sigma}) provides essential independent information. The purpose of this study was to demonstrate a methodology for jointly interpreting crosswell seismic and EM data, in conjunction with detailed constitutive relations between geophysical and reservoir parameters, to quantitatively predict changes in P, S{sub W}, CO{sub 2} gas saturation (S{sub CO2}), CO{sub 2} gas/oil ratio (R{sub CO{sub 2}}), hydrocarbon gas saturation (S{sub g}), and hydrocarbon gas/oil ration (R{sub g}) in a reservoir undergoing CO{sub 2} flood.
Date: July 30, 2002
Creator: Hoversten, G. Michael; Gritto, Roland; Daley, Thomas M.; Majer,Ernest L. & Myer, Larry R.
Partner: UNT Libraries Government Documents Department

Formation dry-out from CO2 injection into saline acquifers: Part 2, Analytical model for salt precipitation

Description: From a mass balance for water dissolved into the flowing CO{sub 2} stream, and a consideration of saturation profiles from the Buckley-Leverett (1942) fractional flow theory, we derive an equation that directly relates gas saturation S{sub g,d} at the dry-out front to temperature, pressure and salinity dependence of fluid properties. The equation is easily solved by iteration or interpolation. From gas saturation at the front we derive the average gas saturation in the dry-out region, from which we obtain the 'solid saturation' S{sub S}, i.e., the fraction of pore space filled with solid precipitate. Values of S{sub S} derived from this theory show excellent agreement with numerical simulations presented in the preceding companion paper ('Part 1'). Thus, from relative permeabilities and fluid properties at in situ conditions prior to CO{sub 2} injection, it is possible to directly make an accurate estimate of solids precipitation, without having to perform a numerical simulation of the injection process.
Date: February 1, 2009
Creator: Pruess, Karsten
Partner: UNT Libraries Government Documents Department

Comparison of Residual Saturation and Capillary Pressure Model for Granular Materials with UNSODA Data

Description: The capillary pressure model correlates drainage and imbibition data from the UNSODA database, provided that the data incorporate the entry head, a minimum displacement required for drainage to begin. According to the model, the imbibition pressure equals the drainage pressures at a critical minimum saturation of 0.301; below this critical saturation, no additional reversible drainage should occur. Some of the UNSODA data sets had a minimum saturation approximately half this value. The difference is attributed to the presence of fissures, which would lower the residual wetting and critical minimum saturations by reducing the fraction of the void volume controlled by capillary pores. If the UNSODA saturations are adjusted for this discrepancy, a probability distribution of minimum saturations for each data set peaks near the predicted critical minimum saturation. Maximum saturations for each data set have a peak near the predicted residual nonwetting saturation of 0.884.
Date: November 1, 2004
Creator: LAURINAT, JAMESE.
Partner: UNT Libraries Government Documents Department

Extensional wave attenuation and velocity in partially-saturated sand in the sonic frequency range

Description: Extensional wave attenuation and velocity measurements on a high permeability Monterey sand were performed over a range of gas saturations for imbibition and degassing conditions. These measurements were conducted using extensional wave pulse propagation and resonance over a 1 - 9 kHz frequency range for a hydrostatic confining pressure of 8.3 MPa. Analysis of the extensional wave data and the corresponding X-ray CT images of the gas saturation show strong attenuation resulting from the presence of the gas (QE dropped from 300 for the dry sand to 30 for the partially-saturated sand), with larger attenuation at a given saturation resulting from heterogeneous gas distributions. The extensional wave velocities are in agreement with Gassmann theory for the test with near-homogeneous gas saturation and with a patchy saturation model for the test with heterogeneous gas saturation. These results show that partially-saturated sands under moderate confining pressure can produce strong intrinsic attenuation for extensional waves.
Date: June 17, 2002
Creator: Liu, Z.; Rector, J.W.; Nihei, K.T.; Tomutsa, L.; Myer, L.R. & Nakagawa, S.
Partner: UNT Libraries Government Documents Department

Extensional wave attenuation and velocity in partially saturated sand in the sonic frequency range

Description: Extensional wave attenuation and velocity measurements on a high permeability Monterey sand were performed over a range of gas saturations for imbibition and degassing conditions. These measurements were conducted using extensional wave pulse propagation and resonance over a 1-9 kHz frequency range for a hydrostatic confining pressure of 8.3 MPa. Analysis of the extensional wave data and the corresponding X-ray CT images of the gas saturation show strong attenuation resulting from the presence of the gas (Q{sub E} dropped from 300 for the dry sand to 30 for the partially-saturated sand), with larger attenuation at a given saturation resulting from heterogeneous gas distributions. The extensional wave velocities are in agreement with Gassmann theory for the test with near-homogeneous gas saturation and with a patchy saturation model for the test with heterogeneous gas saturation. These results show that partially-saturated sands under moderate confining pressure can produce strong intrinsic attenuation for extensional waves.
Date: August 10, 2001
Creator: Liu, Z.; Rector, J.W.; Nihei, K.T.; Tomutsa, L.; Myer, L.R. & Nakagawa, S.
Partner: UNT Libraries Government Documents Department

Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs

Description: During this last period of the ''Seismic Evaluation of Hydrocarbon Saturation in Deep-Water Reservoirs'' project (Grant/Cooperative Agreement DE-FC26-02NT15342), we finalized integration of rock physics, well log analysis, seismic processing, and forward modeling techniques. Most of the last quarter was spent combining the results from the principal investigators and come to some final conclusions about the project. Also much of the effort was directed towards technology transfer through the Direct Hydrocarbon Indicators mini-symposium at UH and through publications. As a result we have: (1) Tested a new method to directly invert reservoir properties, water saturation, Sw, and porosity from seismic AVO attributes; (2) Constrained the seismic response based on fluid and rock property correlations; (3) Reprocessed seismic data from Ursa field; (4) Compared thin layer property distributions and averaging on AVO response; (5) Related pressures and sorting effects on porosity and their influence on DHI's; (6) Examined and compared gas saturation effects for deep and shallow reservoirs; (7) Performed forward modeling using geobodies from deepwater outcrops; (8) Documented velocities for deepwater sediments; (9) Continued incorporating outcrop descriptive models in seismic forward models; (10) Held an open DHI symposium to present the final results of the project; (11) Relations between Sw, porosity, and AVO attributes; (12) Models of Complex, Layered Reservoirs; and (14) Technology transfer Several factors can contribute to limit our ability to extract accurate hydrocarbon saturations in deep water environments. Rock and fluid properties are one factor, since, for example, hydrocarbon properties will be considerably different with great depths (high pressure) when compared to shallow properties. Significant over pressure, on the other hand will make the rocks behave as if they were shallower. In addition to the physical properties, the scale and tuning will alter our hydrocarbon indicators. Gas saturated reservoirs change reflection amplitudes significantly. The goal for the final ...
Date: April 30, 2006
Creator: Batzle, Michael
Partner: UNT Libraries Government Documents Department

Evaluation of linear solvers for oil reservoir simulation problems. Part 2: The fully implicit case

Description: A previous paper [Joubert/Biswas 1997] contained investigations of linear solver performance for matrices arising from Amoco`s Falcon parallel oil reservoir simulation code using the IMPES formulation (implicit pressure, explicit saturation). In this companion paper, similar issues are explored for linear solvers applied to matrices arising from more difficult fully implicit problems. The results of numerical experiments are given.
Date: December 1, 1997
Creator: Joubert, W. & Janardhan, R.
Partner: UNT Libraries Government Documents Department

Modeling geologic storage of carbon dioxide: Comparison ofnon-hysteretic and hysteretic characteristic curves

Description: Numerical models of geologic storage of carbon dioxide (CO2)in brine-bearing formations use characteristic curves to represent theinteractions of non-wetting-phase CO2 and wetting-phase brine. When aproblem includes both injection of CO2 (a drainage process) and itssubsequent post-injection evolution (a combination of drainage andwetting), hysteretic characteristic curves are required to correctlycapture the behavior of the CO2 plume. In the hysteretic formulation,capillary pressure and relative permeability depend not only on thecurrent grid-block saturation, but also on the history of the saturationin the grid block. For a problem that involves only drainage or onlywetting, a non-hysteretic formulation, in which capillary pressure andrelative permeability depend only on the current value of the grid-blocksaturation, is adequate. For the hysteretic formulation to be robustcomputationally, care must be taken to ensure the differentiability ofthe characteristic curves both within and beyond the turning-pointsaturations where transitions between branches of the curves occur. Twoexample problems involving geologic CO2 storage are simulated withTOUGH2, a multiphase, multicomponent code for flow and transport codethrough geological media. Both non-hysteretic and hysteretic formulationsare used, to illustrate the applicability and limitations ofnon-hysteretic methods.The first application considers leakage of CO2from the storage formation to the ground surface, while the secondexamines the role of heterogeneity within the storageformation.
Date: July 17, 2006
Creator: Doughty, Christine
Partner: UNT Libraries Government Documents Department

Modeling geologic storage of carbon dioxide: Comparison ofnon-hysteretic chracteristic curves

Description: TOUGH2 models of geologic storage of carbon dioxide (CO2) in brine-bearing formations use characteristic curves to represent the interactions of non-wetting-phase CO2 and wetting-phase brine. When a problem includes both injection of CO2 (a drainage process) and its subsequent post-injection evolution (a combination of drainage and wetting), hysteretic characteristic curves are required to correctly capture the behavior of the CO2 plume. In the hysteretic formulation, capillary pressure and relative permeability depend not only on the current grid-block saturation, but also on the history of the saturation in the grid block. For a problem that involves only drainage or only wetting, a nonhysteretic formulation, in which capillary pressure and relative permeability depend only on the current value of the grid-block saturation, is adequate. For the hysteretic formulation to be robust computationally, care must be taken to ensure the differentiability of the characteristic curves both within and beyond the turning-point saturations where transitions between branches of the curves occur. Two example problems involving geologic CO2 storage are simulated using non-hysteretic and hysteretic models, to illustrate the applicability and limitations of non-hysteretic methods: the first considers leakage of CO2 from the storage formation to the ground surface, while the second examines the role of heterogeneity within the storage formation.
Date: April 28, 2006
Creator: Doughty, Christine
Partner: UNT Libraries Government Documents Department

Hydrogen adsorption on Ru(001) studied by Scanning TunnelingMicroscopy

Description: The adsorption of hydrogen on Ru(001) was studied by scanning tunneling microscopy at temperatures around 50 K. Hydrogen was found to adsorb dissociatively forming different ordered structures as a function of coverage. In order of increasing coverage {theta} in monolayers (ML) these were ({radical}3 x {radical}3)r30{sup o} at {theta} = 0.3 ML; (2 x 1) at {theta} = 0.50 ML, (2 x 2)-3H at {theta} = 0.75, and (1 x 1) at {theta} = 1.00. Some of these structures were observed to coexist at intermediate coverage values. Close to saturation of 1 ML, H-vacancies (unoccupied three fold fcc hollow Ru sites) were observed either as single entities or forming transient aggregations. These vacancies diffuse and aggregate to form active sites for the dissociative adsorption of hydrogen.
Date: January 18, 2008
Creator: Tatarkhanov, Mous; Rose, Franck; Fomin, Evgeny; Ogletree, D.Frank & Salmeron, Miquel
Partner: UNT Libraries Government Documents Department

EIGENMODE ANALYSIS OF OPTICAL GUIDING IN FREE ELECTRON LASERS

Description: The spatial properties of the optical field and hence the performance of a free electron laser depend on the fact that the electron beam, which acts as both an amplifying and a refractive medium, is transversely nonuniform. Under certain circumstances, optical guiding may be realized, where the optical field is stably confined near the electron beam and amplified along the beam over many Rayleigh ranges. We show that the three-dimensional evolution of the optical field through the interaction region can be determined by a guided mode expansion before saturation. Optical guiding occurs when the fundamental growing mode becomes dominant. The guided mode expansion is made possible by implementing the biorthogonality of the eigenmodes of the coupled electron-beam-optical-wave system. The eigenmodes are found to be of vectorial form with three components; one specifies the guided optical mode and the other two describe the density and the energy modulations of the electron beam.
Date: March 1, 1989
Creator: Xie, M.; Deacon, D.A.G. & Madey, J.M.J.
Partner: UNT Libraries Government Documents Department

Multi-Regional Reactive Transport Due to Strong Anisotropy in Unsaturated Soils with Evolving Scales of Heterogeneity

Description: Anisotropic and heterogeneous flow in unsaturated porous media is dependent on saturation conditions, and currently there exist limited options that adequately model this phenomenon. The phenomenon of lateral spreading commonly attributed to anisotropy can move contaminants beyond compliance boundaries at unexpected velocitites essentially bypassing large regions of the subsurface.
Date: October 13, 2006
Creator: Mo, Xinghua
Partner: UNT Libraries Government Documents Department

Inference of ICF Implosion Core Mix using Experimental Data and Theoretical Mix Modeling

Description: The mixing between fuel and shell materials in Inertial Confinement Fusion (ICF) implosion cores is a current topic of interest. The goal of this work was to design direct-drive ICF experiments which have varying levels of mix, and subsequently to extract information on mixing directly from the experimental data using spectroscopic techniques. The experimental design was accomplished using hydrodynamic simulations in conjunction with Haan's saturation model, which was used to predict the mix levels of candidate experimental configurations. These theoretical predictions were then compared to the mixing information which was extracted from the experimental data, and it was found that Haan's mix model performed well in predicting trends in the width of the mix layer. With these results, we have contributed to an assessment of the range of validity and predictive capability of the Haan saturation model, as well as increased our confidence in the methods used to extract mixing information from experimental data.
Date: April 30, 2008
Creator: Welser-Sherrill, L; Haynes, D A; Mancini, R C; Cooley, J H; Tommasini, R; Golovkin, I E et al.
Partner: UNT Libraries Government Documents Department

SPECTRAL AMPLITUDE AND PHASE EVOLUTION IN PETAWATT LASER PULSES

Description: The influence of the active gain medium on the spectral amplitude and phase of amplified pulses in a CPA system is studied. Results from a 10-PW example based on Nd-doped mixed glasses are presented. In conclusion, this study shows that, by using spectral shaping and gain saturation in a mixed-glass amplifier, it is possible to produce 124 fs, 1.4 kJ laser pulses. One detrimental effect, the pulse distortion due to resonant amplification medium, has been investigated and its magnitude as well as its compensation calculated.
Date: November 22, 2010
Creator: Filip, C V
Partner: UNT Libraries Government Documents Department