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A chaotic-dynamical conceptual model to describe fluid flow and contaminant transport in a fractured vadose zone. 1997 progress report and presentations at the annual meeting, Ernest Orlando Lawrence Berkeley National Laboratory, December 3--4, 1997

Description: Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, the authors examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to develop a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, they measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which they try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predict the long-term bounds on fluid flow and transport behavior, known as the attractor of the system, and to examine the limits of short-term predictability within these bounds. This approach is especially well suited to the need for short-term predictions to support remediation decisions and long-term bounding studies. View-graphs from ten presentations made at the annual meeting held December 3--4, 1997 are included in an appendix to this report.
Date: July 1, 1998
Creator: Faybishenko, B.; Doughty, C. & Geller, J.
Partner: UNT Libraries Government Documents Department

ITOUGH2 sample problems

Description: This report contains a collection of ITOUGH2 sample problems. It complements the ITOUGH2 User`s Guide [Finsterle, 1997a], and the ITOUGH2 Command Reference [Finsterle, 1997b]. ITOUGH2 is a program for parameter estimation, sensitivity analysis, and uncertainty propagation analysis. It is based on the TOUGH2 simulator for non-isothermal multiphase flow in fractured and porous media [Preuss, 1987, 1991a]. The report ITOUGH2 User`s Guide [Finsterle, 1997a] describes the inverse modeling framework and provides the theoretical background. The report ITOUGH2 Command Reference [Finsterle, 1997b] contains the syntax of all ITOUGH2 commands. This report describes a variety of sample problems solved by ITOUGH2. Table 1.1 contains a short description of the seven sample problems discussed in this report. The TOUGH2 equation-of-state (EOS) module that needs to be linked to ITOUGH2 is also indicated. Each sample problem focuses on a few selected issues shown in Table 1.2. ITOUGH2 input features and the usage of program options are described. Furthermore, interpretations of selected inverse modeling results are given. Problem 1 is a multipart tutorial, describing basic ITOUGH2 input files for the main ITOUGH2 application modes; no interpretation of results is given. Problem 2 focuses on non-uniqueness, residual analysis, and correlation structure. Problem 3 illustrates a variety of parameter and observation types, and describes parameter selection strategies. Problem 4 compares the performance of minimization algorithms and discusses model identification. Problem 5 explains how to set up a combined inversion of steady-state and transient data. Problem 6 provides a detailed residual and error analysis. Finally, Problem 7 illustrates how the estimation of model-related parameters may help compensate for errors in that model.
Date: November 1, 1997
Creator: Finsterle, S.
Partner: UNT Libraries Government Documents Department

Laboratory studies of groundwater degassing in replicas of natural fractured rock for linear flow geometry

Description: Laboratory experiments to simulate two-phase (gas and water) flow in fractured rock evolving from groundwater degassing were conducted in transparent replicas of natural rock fractures. These experiments extend the work by Geller et al. (1995) and Jarsjo and Geller (1996) that tests the hypothesis that groundwater degassing caused observed flow reductions in the Stripa Simulated Drift Experiment (SDE). Understanding degassing effects over a range of gas contents is needed due to the uncertainty in the gas contents of the water at the SDE. The main objectives of this study were to: (1) measure the effect of groundwater degassing on liquid flow rates for lower gas contents than the values used in Geller for linear flow geometry in the same fracture replicas of Geller; (2) provide a data set to develop a predictive model of two-phase flow in fractures for conditions of groundwater degassing; and (3) improve the certainty of experimental gas contents (this effort included modifications to the experimental system used by Geller et al. and separate gas-water equilibration tests). The Stripa site is being considered for a high-level radioactive waste repository.
Date: February 1, 1998
Creator: Geller, J.T.
Partner: UNT Libraries Government Documents Department

Modifications and additions to selected TOUGH2 modules

Description: The purpose of this report is to provide all software baseline documents necessary for the software qualification of the revised versions of the selected TOUGH2 modules, which include single-phase gas (EOS1G), effective continuum method (EOS3/ECM), saturated/unsaturated flow (EOS9), and radionuclide transport (T2R3D) modules of the TOUGH2 code. TOUGH2 is a numerical simulation code for multi-dimensional, coupled fluid and heat flow of multiphase, multicomponent fluid mixtures in porous and fractured media. This report augments the document Software Qualification of Selected TOUGH2 modules. This report contains the following sections: (1) requirement specifications and code development and (2) software validation test plan and results. These sections comprise sequential parts of Software Lifecycle, and should be used in conjunction with the TOUGH User`s Guide, TOUGH2 documentation, TOUGH2 Software Qualification, and Software Qualification of Selected TOUGH2 modules. The version of TOUGH2 used with the software being qualified herein is the October 1996 Standard Version 1.2, as qualified in Wu et al. (1996) and housed at the Department of Energy`s Energy Science and Technology Software Center (ESTSC) in Oak Ridge, Tennessee.
Date: January 1, 1998
Creator: Wu, Y.S. & Mishra, A.K.
Partner: UNT Libraries Government Documents Department

New 3D parallel GILD electromagnetic modeling and nonlinear inversion using global magnetic integral and local differential equation

Description: This paper describes a new 3D parallel GILD electromagnetic (EM) modeling and nonlinear inversion algorithm. The algorithm consists of: (a) a new magnetic integral equation instead of the electric integral equation to solve the electromagnetic forward modeling and inverse problem; (b) a collocation finite element method for solving the magnetic integral and a Galerkin finite element method for the magnetic differential equations; (c) a nonlinear regularizing optimization method to make the inversion stable and of high resolution; and (d) a new parallel 3D modeling and inversion using a global integral and local differential domain decomposition technique (GILD). The new 3D nonlinear electromagnetic inversion has been tested with synthetic data and field data. The authors obtained very good imaging for the synthetic data and reasonable subsurface EM imaging for the field data. The parallel algorithm has high parallel efficiency over 90% and can be a parallel solver for elliptic, parabolic, and hyperbolic modeling and inversion. The parallel GILD algorithm can be extended to develop a high resolution and large scale seismic and hydrology modeling and inversion in the massively parallel computer.
Date: July 1, 1998
Creator: Xie, G.; Li, J.; Majer, E. & Zuo, D.
Partner: UNT Libraries Government Documents Department

Sensitivity study on hydraulic well testing inversion using simulated annealing

Description: For environmental remediation, management of nuclear waste disposal, or geothermal reservoir engineering, it is very important to evaluate the permeabilities, spacing, and sizes of the subsurface fractures which control ground water flow. Cluster variable aperture (CVA) simulated annealing has been used as an inversion technique to construct fluid flow models of fractured formations based on transient pressure data from hydraulic tests. A two-dimensional fracture network system is represented as a filled regular lattice of fracture elements. The algorithm iteratively changes an aperture of cluster of fracture elements, which are chosen randomly from a list of discrete apertures, to improve the match to observed pressure transients. The size of the clusters is held constant throughout the iterations. Sensitivity studies using simple fracture models with eight wells show that, in general, it is necessary to conduct interference tests using at least three different wells as pumping well in order to reconstruct the fracture network with a transmissivity contrast of one order of magnitude, particularly when the cluster size is not known a priori. Because hydraulic inversion is inherently non-unique, it is important to utilize additional information. The authors investigated the relationship between the scale of heterogeneity and the optimum cluster size (and its shape) to enhance the reliability and convergence of the inversion. It appears that the cluster size corresponding to about 20--40 % of the practical range of the spatial correlation is optimal. Inversion results of the Raymond test site data are also presented and the practical range of spatial correlation is evaluated to be about 5--10 m from the optimal cluster size in the inversion.
Date: November 1, 1997
Creator: Nakao, Shinsuke; Najita, J. & Karasaki, Kenzi
Partner: UNT Libraries Government Documents Department

Comparison of scale analysis and numerical simulation for saturated zone convective mixing processes

Description: Scale analysis can be used to predict a variety of quantities arising from natural systems where processes are described by partial differential equations. For example, scale analysis can be applied to estimate the effectiveness of convective missing on the dilution of contaminants in groundwater. Scale analysis involves substituting simple quotients for partial derivatives and identifying and equating the dominant terms in an order-of-magnitude sense. For free convection due to sidewall heating of saturated porous media, scale analysis shows that vertical convective velocity in the thermal boundary layer region is proportional to the Rayleigh number, horizontal convective velocity is proportional to the square root of the Rayleigh number, and thermal boundary layer thickness is proportional to the inverse square root of the Rayleigh number. These scale analysis estimates are corroborated by numerical simulations of an idealized system. A scale analysis estimate of mixing time for a tracer mixing by hydrodynamic dispersion in a convection cell also agrees well with numerical simulation for two different Rayleigh numbers. Scale analysis for the heating-from-below scenario produces estimates of maximum velocity one-half as large as the sidewall case. At small values of the Rayleigh number, this estimate is confirmed by numerical simulation. For larger Rayleigh numbers, simulation results suggest maximum velocities are similar to the sidewall heating scenario. In general, agreement between scale analysis estimates and numerical simulation results serves to validate the method of scale analysis. Application is to radioactive repositories.
Date: June 1, 1998
Creator: Oldenburg, C. M.
Partner: UNT Libraries Government Documents Department

Enhanced data analysis for the VZMS: Conceptual model design and initial application for the Vadose Zone Monitoring System (VZMS), McClellan AFB. 1998 semi-annual report

Description: The VZMS project at McClellan AFB involves both vadose zone data collection as well as enhanced data analysis. The purpose of enhanced data analysis is to develop conceptual models to carry out model validation and evaluation, as well as sensitivity and predictive modeling studies. Enhanced data analysis consists primarily of T2VOC forward simulations and ITOUGH2 inverse modeling. The methodology the authors employ in the VZMS project involves developing a conceptual model and iteratively updating it based on the agreement between model results and VZMS data. They demonstrate the development of an initial T2VOC conceptual model for the S-7 site based on data from instrument cluster VZMS-B. Lithologic data from the drilling logs along with empirical relations for estimating permeability and sediment moisture retention characteristics are used to define the layering of four different sediment types. The authors adjusted the layering of the sediments manually until the sediment moisture content profile from the T2VOC simulation of the gravity-capillary equilibrium agreed well with observed neutron probe data. Using this updated conceptual model, they performed inverse modeling using ITOUGH2 to find bet-fit absolute permeability values based on the minimization of differences between simulated and actual soil-gas pressure measurements.
Date: June 14, 1998
Creator: James, A. L. & Oldenburg, C. M.
Partner: UNT Libraries Government Documents Department

EOS9nT: A TOUGH2 module for the simulation of flow and solute/colloid transport

Description: EOS9nT is a new TOUGH2 module for the simulation of flow and transport of an arbitrary number n of tracers (solutes and/or colloids) in the subsurface. The module first solves the flow-related equations, which are comprised of (a) the Richards equation and, depending on conditions, may also include (b) the flow equation of a dense brine or aqueous suspension and/or (c) the heat equation. A second set of transport equations, corresponding to the n tracers, are then solved sequentially. The low concentrations of the n tracers are considered to have no effect on the liquid phase, thus making possible the decoupling of their equations. The first set of equations in EOS9nT provides the flow regime and account for fluid density variations due to thermal and/or solute concentration effects. The n tracer transport equations account for sorption, radioactive decay, advection, hydrodynamic dispersion, molecular diffusion, as well as filtration (for colloids only). EOS9nT can handle gridblocks or irregular geometry in three-dimensional domains. Preliminary results from four 1-D verification problems show an excellent agreement between the numerical predictions and the known analytical solutions.
Date: April 1, 1998
Creator: Moridis, G.J.; Wu, Y.S. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Experimental investigation of magnetically driven flow of ferrofluids in porous media

Description: This report presents experimental results of the flow of ferrofluids in porous media to investigate the potential for precisely controlling fluid emplacement in porous media using magnetic fields. Ferrofluids are colloidal suspensions of magnetic particles stabilized in various carrier liquids. In the presence of an external magnetic field, the ferrofluid becomes magnetized as the particles align with the magnetic field. Potential applications of ferrofluids to subsurface contamination problems include magnetic guidance of reactants to contaminated target zones in the subsurface for in situ treatment or emplacement of containment barriers. Laboratory experiments of magnetically induced ferrofluid flow in porous media in this report demonstrate the potential for mobilizing ferrofluid and controlling fluid emplacement through control of the external magnetic field. The pressures measured in ferrofluid due to the attraction of ferrofluid to a permanent magnet agree well with calculated values. The results show that a predictable pressure gradient is produced in the fluid which is strong near the magnet and drops off quickly with distance. This pressure gradient drives the fluid through sand without significant loss of ferrofluid strength due to filtration or dilution. Flow visualization experiments of ferrofluid in water-filled horizontal Hele-Shaw cells demonstrate that ferrofluid obtains a consistent final arc-shaped configuration around the magnet regardless of initial configuration or flow path toward the magnet. Analogous experiments in actual porous media showed similar features and confirm the ability of ferrofluid to move through porous media by magnetic forces.
Date: August 1, 1998
Creator: Borglin, S.E.; Moridis, G.J. & Oldenburg, C.M.
Partner: UNT Libraries Government Documents Department

ITOUGH2 V3.2 verification and validation report

Description: This report describes the Verification and Validation (V and V) test cases performed to qualify ITOUGH2 V3.2. ITOUGH2 V3.2 was installed in a directory {approximately}/itough2v3.2 on a SUN ULTRA 1 workstation under UNIX Solaris 2. Instructions for installing ITOUGH2 can be found in file read.me and the user`s manual. This report is structured as follows: for each functional requirement, the corresponding design is described, which may include the mathematical model implemented in ITOUGH2 V3.2, if appropriate. Next, the author discusses the test case or sequence of test cases performed to validate each requirement, followed by a description of the test results and their compliance with the acceptance criteria. ITOUGH2 simulates fluid flow in fractures.
Date: June 1, 1998
Creator: Finsterle, S.
Partner: UNT Libraries Government Documents Department

Multiphase inverse modeling: An Overview

Description: Inverse modeling is a technique to derive model-related parameters from a variety of observations made on hydrogeologic systems, from small-scale laboratory experiments to field tests to long-term geothermal reservoir responses. If properly chosen, these observations contain information about the system behavior that is relevant to the performance of a geothermal field. Estimating model-related parameters and reducing their uncertainty is an important step in model development, because errors in the parameters constitute a major source of prediction errors. This paper contains an overview of inverse modeling applications using the ITOUGH2 code, demonstrating the possibilities and limitations of a formalized approach to the parameter estimation problem.
Date: March 1, 1998
Creator: Finsterle, S.
Partner: UNT Libraries Government Documents Department

New 3D parallel SGILD modeling and inversion

Description: In this paper, a new parallel modeling and inversion algorithm using a Stochastic Global Integral and Local Differential equation (SGILD) is presented. The authors derived new acoustic integral equations and differential equation for statistical moments of the parameters and field. The new statistical moments integral equation on the boundary and local differential equations in domain will be used together to obtain mean wave field and its moments in the modeling. The new moments global Jacobian volume integral equation and the local Jacobian differential equations in domain will be used together to update the mean parameters and their moments in the inversion. A new parallel multiple hierarchy substructure direct algorithm or direct-iteration hybrid algorithm will be used to solve the sparse matrices and one smaller full matrix from domain to the boundary, in parallel. The SGILD modeling and imaging algorithm has many advantages over the conventional imaging approaches. The SGILD algorithm can be used for the stochastic acoustic, electromagnetic, and flow modeling and inversion, and are important for the prediction of oil, gas, coal, and geothermal energy reservoirs in geophysical exploration.
Date: September 1, 1998
Creator: Xie, G.; Li, J. & Majer, E.
Partner: UNT Libraries Government Documents Department

Numerical modeling of field tests in unsaturated fractured basalt at the Box Canyon site

Description: A TOUGH2 model of a ponded infiltration test has been developed and used to predict the results of a field experiment conducted in the vadose zone of the fractured Snake River Plain basalts, at the Box Canyon site in southeastern idaho. The key question addressed is how fracture-pattern characteristics and connectivity affect the pattern of liquid infiltration. The numerical model, a two-dimensional vertical cross-section, uses half-meter discretization for the shallow field site, which extends about 20 m from the ground surface to an underlying perched water body. The model includes explicit but highly simplified representations of major fractures and other important hydrological features. It adequately reproduces the majority of the field observations, confirming the notion that infiltration is largely fracture-controlled.
Date: May 1, 1998
Creator: Doughty, C.
Partner: UNT Libraries Government Documents Department

Theoretical and experimental investigations of ferrofluids for guiding and detecting liquids in the subsurface. FY 1997 annual report

Description: Ferrofluids are stable colloidal suspensions of magnetic particles in various carrier liquids with high saturation magnetizations, which can be manipulated in virtually any fashion, defying gravitational or viscous forces in response to external magnetic fields. In this report, the authors review the results of their investigation of the potential of ferrofluids (1) to accurately and effectively guide reactants (for in-situ treatment) or barrier liquids (low-viscosity permeation grouts) to contaminated target zones in the subsurface using electromagnetic forces, and (2) to trace the movement and position of liquids injected in the subsurface using geophysical methods. They investigate the use of ferrofluids to enhance the efficiency of in-situ treatment and waste containment through (a) accurate guidance and delivery of reagent liquids to the desired subsurface contamination targets and/or (b) effective sweeping of the contaminated zone as ferrofluids move from the application point to an attracting magnet/collection point. They also investigate exploiting the strong magnetic signature of ferrofluids to develop a method for monitoring of liquid movement and position during injection using electromagnetic methods. The authors demonstrated the ability to induce ferrofluid movement in response to a magnetic field, and measured the corresponding magnetopressure. They demonstrated the feasibility of using conventional magnetometry for detecting subsurface zones of various shapes containing ferrofluids for tracing liquids injected for remediation or barrier formation. Experiments involving spherical, cylindrical and horizontal slabs showed a very good agreement between predictions and measurements.
Date: March 1, 1998
Creator: Moridis, G.J.; Borglin, S.E.; Oldenburg, C.M. & Becker, A.
Partner: UNT Libraries Government Documents Department

A Compilation of Data on Fluids from Geothermal Resources in the United States

Description: This report is part of the Lawrence Berkeley Laboratory work to compile data of characteristics of the main U.S. geothermal source areas. The purpose of this compilation is to provide information on the chemistry of geothermal fluids to scientists and engineers involved with the development of liquid dominated geothermal energy resources. The compilation is a comprehensive tabulation of available geothermal fluid data from the most important geothermal resources in the United States. [Abstracter's note: This was part of a large but short-lived effort at LBNL to collect lots of geothermal data. There may be other reports that are worth searching for to add to the Geothermal Legacy collection at OSTI. DJE-2005]
Date: May 1, 1978
Creator: Cosner, S.R. & Apps, J.A.
Partner: UNT Libraries Government Documents Department

Effect of Measured Wellhead Parameters and Well Scaling on the Computed Downhole Conditions in Cerro Prieto Wells

Description: This paper is devoted to the discussion of the wellbore model and its describing equations, comparison between the computed and measured pressures and the effect of measured wellhead parameters on the downhole pressures in the well. Finally a wellbore model with multiple inside diameters is discussed and the effect of well scaling on the bottom hole pressures is studied.
Date: December 16, 1980
Creator: Goyal, K.P.; Miller, C.W. & Lippmann, M.J.
Partner: UNT Libraries Government Documents Department

Eliminating the Wellbore Response in Transient Well Test Analysis

Description: The main purpose of this work is to show that it is possible to calculate the sandface flowrate given wellhead conditions and the downhole pressure transients. It is not necessary t o know anything about the reservoir itself. First, it is of interest to look at the nonuniform pressure changes in the well, and to illustrate nonisothermal effects on pressure transient data.
Date: December 16, 1980
Creator: Miller, Constance W.
Partner: UNT Libraries Government Documents Department

Enhancement of Steam Phase Relative Permeability Due to Phase Transformation Effects in Porous Media

Description: An experimental study of two-phase concurrent flow of steam and water conducted (Verma et al., 1985) and a set of relative permeability curves was obtained. These curves were compared with semi-empirical results (Brooks and Corey, 1964) and experimental results obtained by other investigators (Johnson et al., 1959, and Osoba et al., 1951) for two-phase, two-component flow (oil/gas; gas/water; gas/oil). It was found that while the wetting phase relative permeabilities were in good agreement, the relative permeability for the steam phase was considerably higher than the relative permeabilities of the non-wetting phase (oil in oil/water and non-condensing gas in gas/oil or gas/water) in two-component systems (Figs. 1 and 2). This enhancement of steam relative permeability is attributed to phase transformation effects at the pore level in flow channels. There are two separate mechanisms by which phase transformation affected relative permeability CUTVBS (1) phase transformation in converging-diverging flow channels with hydrophilic walls can cause an enhancement of steam phase relative permeability; and (2) phase transformation along the interface of a stagnant phase and the phase flowing around it controls the irreducible phase saturation of the stagnant phase (Verma, 1986). A pore level model was considered to study the first mechanism. In this model a pore space, shown in Figure 3, is idealized as a toroidal flow channel (Fig. 4) with a throat radius r, and pore body radius rb. Flow of steam and water through the throat portion of a pore was modeled using the MULKOM simulator (Pruess, 1983). The results indicate that when steam encounters a pore throat of a highly constricted flow channel in high conductivity solid, a fraction of the flowing steam condenses upstream from the constriction, depositing its latent heat of condensation. This heat is conducted through the solid grains around the pore throat, and evaporation takes place ...
Date: January 21, 1986
Creator: Verma, A. & Pruess, K.
Partner: UNT Libraries Government Documents Department

Quantitative Model of the Cerro Prieto Field

Description: A three-dimensional model of the Cerro Prieto geothermal field, Mexico, is under development. It is based on an updated version of LBL's hydrogeologic model of the field. It takes into account major faults and their effects on fluid and heat flow in the system. First, the field under natural state conditions is modeled. The results of this model match reasonably well observed pressure and temperature distributions. Then, a preliminary simulation of the early exploitation of the field is performed. The results show that the fluid in Cerro Prieto under natural state conditions moves primarily from east to west, rising along a major normal fault (Fault H). Horizontal fluid and heat flow occurs in a shallower region in the western part of the field due to the presence of permeable intergranular layers. Estimates of permeabilities in major aquifers are obtained, and the strength of the heat source feeding the hydrothermal system is determined.
Date: January 21, 1986
Creator: Halfman, S.E.; Lippmann, M.J. & Bodvarsson, G.S.
Partner: UNT Libraries Government Documents Department

TOUGH90: A FORTRAN90 implementation of TOUGH2

Description: TOUGH90 is a FORTRAN90 implementation of TOUGH2, and represents a major change in syntax and architecture over TOUGH2, while maintaining full backward compatibility with existing input data files. The main features of TOUGH90 include dynamic memory management, the use of modules, derived types, array operations, matrix manipulation, and new and very powerful intrinsic procedures. These result in a faster, more efficient and compact code, which is conceptually simpler, and significantly easier to modify and upgrade.
Date: April 1, 1998
Creator: Moridis, G.J.
Partner: UNT Libraries Government Documents Department

Using TRINET for simulating flow and transport in porous media

Description: The finite element model TRINET calculates transient or steady-state fluid flow and solute transport on a lattice composed of one-dimensional finite elements (i.e., pipes) of porous medium. TRINET incorporates an adaptive gridding algorithm to minimize numerical dispersion for transport calculations. Although TRINET was originally developed to study fracture networks, the primary interest here is in applying TRINET more generally to simulate transport in porous media (or a fractured medium being treated as an effective continuum). This requires developing expressions to relate TRINET inputs to equivalent parameters used to describe flow and transport in homogeneous porous media. In this report, the authors briefly describe the basic TRINET formulation for flow and transport, present TRINET equivalences for porous medium parameters, and compare TRINET to analytical solutions using the proposed porous medium equivalents.
Date: August 1, 1998
Creator: Najita, J. & Doughty, C.
Partner: UNT Libraries Government Documents Department

Decline Curve Analysis of Production Data from the Geysers Geothermal Field

Description: Production data for over two hundred wells at The Geysers geothermal field were compiled and analysed. Decline curves for groups of wells with 5, 10, and 40 acre spacing are presented and compared to curves published previously by Budd (1972) and Dykstra (1981). Decline curves for several individual wells and leases are discussed to illustrate the effects of well spacing and location, as well as the heterogeneous nature of the reservoir. 6 figs., 1 tab., 10 refs.
Date: January 20, 1987
Creator: Ripperda, M. & Bodvarsson, G.S.
Partner: UNT Libraries Government Documents Department

Geothermal Field Case Studies that Document the Usefulness of Models in Predicting Reservoir and Well Behavior

Description: The geothermal industry has shown significant interest in case histories that document field production histories and demonstrate the techniques which work best in the characterization and evaluation of geothermal systems. In response to this interest, LBL has devoted a significant part of its geothermal program to the compilation and analysis of data from US and foreign fields (e.g., East Mesa, The Geysers, Susanville, and Long Valley in California; Klamath Fall in Oregon; Valles Caldera, New Mexico; Cerro Prieto and Los Azufres in Mexico; Krafla and Nesjavellir in Iceland; Larderello in Italy; Olkaria in Kenya). In each of these case studies we have been able to test and validate in the field, or against field data, the methodology and instrumentation developed under the Reservoir Technology Task of the DOE Geothermal Program, and to add to the understanding of the characteristics and processes occurring in geothermal reservoirs. Case study results of the producing Cerro Prieto and Olkaria geothermal fields are discussed in this paper. These examples were chosen because they illustrate the value of conceptual and numerical models to predict changes in reservoir conditions, reservoir processes, and well performance that accompany field exploitation, as well as to reduce the costs associated with the development and exploitation of geothermal resources.
Date: March 21, 1989
Creator: Lippmann, Marcelo J.
Partner: UNT Libraries Government Documents Department