Download or read book Simulation of Fluid rock Interactions in a Geothermal Basin Final Report QUAGMR quasi active Geothermal Reservoir written by and published by . This book was released on 1975 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: General balance laws and constitutive relations are developed for convective hydrothermal geothermal reservoirs. A fully interacting rock-fluid system is considered; typical rock-fluid interactions involve momentum and energy transfer and the dependence of rock porosity and permeability upon the fluid and rock stresses. The mathematical model also includes multiphase (water/steam) effects. A simple analytical model is employed to study heat transfer into/or from a fluid moving in a porous medium. Numerical results show that for fluid velocities typical of geothermal systems (Reynolds number much less than 10), the fluid and the solid may be assumed to be in local thermal equilibrium. Mathematical formalism of Anderson and Jackson is utilized to derive a continuum species transport equation for flow in porous media; this method allows one to delineate, in a rigorous manner, the convective and diffusive mechanisms in the continuum representation of species transport. An existing computer program (QUAGMR) is applied to study upwelling of hot water from depth along a fault; the numerical results can be used to explain local temperature inversions occasionally observed in bore hole measurements.

Download or read book Simulation of Fluid rock Interactions in a Geothermal Basin written by S. K. Garg and published by . This book was released on 1975 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Simulation of Water rock Interaction in the Yellowstone Geothermal System Using TOUGHREACT written by and published by . This book was released on 2003 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to simulate the chemical and hydrological effects of water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8 C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to simulate the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Download or read book Reactive Flow Modeling of Hydrothermal Systems written by Michael Kühn and published by Springer. This book was released on 2004-03-24 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book introduces the topic of geochemical modeling of fluids in subsurface and hydrothermal systems. The intention is to serve as a textbook for graduate students in aqueous, environmental and groundwater geochemistry, despite the fact that its focus is on the special topic of geochemistry in hydrothermal systems, it also provides new insights for experienced researchers with respect to the topic of reactive transport. The overall purpose is to give the reader an understanding of the processes that control the chemical composition of waters in hydrothermal systems and to highlight the interfaces between chemistry, geothermics and hydrogeology. From the reviews: "..is a nice, compact introduction to the principles of modeling coupled fluid flow and fluid-mineral reactions in active geothermal systems, as used for heating and electricity generation." ( Christoph A. Heinrich, ECONOMIC GEOLOGY, June 2004)

Download or read book Simulation of Water rock Interaction in the Yellowstone Geothermal System Using TOUGHREACT written by P. F. Dobson and published by . This book was released on 2003 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Yellowstone geothermal system provides an ideal opportunity to test the ability of reactive transport models to accurately simulate water-rock interaction. Previous studies of the Yellowstone geothermal system have characterized water-rock interaction through analysis of rocks and fluids obtained from both surface and downhole samples. Fluid chemistry, rock mineralogy, permeability, porosity, and thermal data obtained from the Y-8 borehole in Upper Geyser Basin were used to constrain a series of reactive transport simulations of the Yellowstone geothermal system using TOUGHREACT. Three distinct stratigraphic units were encountered in the 153.4 m deep Y-8 drill core: volcaniclastic sandstone, perlitic rhyolitic lava, and nonwelded pumiceous tuff. The main alteration phases identified in the Y-8 core samples include clay minerals, zeolites, silica polymorphs, adularia, and calcite. Temperatures observed in the Y-8 borehole increase with depth from sub-boiling conditions at the surface to a maximum of 169.8 C at a depth of 104.1 m, with near-isothermal conditions persisting down to the well bottom. 1-D models of the Y-8 core hole were constructed to determine if TOUGHREACT could accurately predict the observed alteration mineral assemblage given the initial rock mineralogy and observed fluid chemistry and temperatures. Preliminary simulations involving the perlitic rhyolitic lava unit are consistent with the observed alteration of rhyolitic glass to form celadonite.

Download or read book Water Rock Experiments to 300oC and Comparisons to Chemical Interactions in Active Geothermal Systems written by George H. Kacandes and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Basaltic rocks have been reacted with synthetic groundwater in closed-system, Dickson-type rocking autoclaves for periods of up to 5,000 hours. The experiments were carried out isothermally at 100°, 200°, and 300° C, 300 bars, and an initial water/rock mass ratio of 10. These conditions were intended to simulate those present in active geothermal systems. Fluid compositions changed rapidly during the early stages of the experiments. In the long-term, however, most species approached steady-state values. At that stage, temperature appears to be the most important factor controlling fluid composition; the effect of rock type and starting fluid composition were far less significant. Comparison of long-term, stabilized fluid compositions with those produced in other dilute-water/whole-rock experiments (basaltic and non-basaltic) shows that experiments conducted at the same temperature attain similar overall fluid chemistries. Such behavior may reflect an approach to equilibrium of these fluids with thermochemically-similar alteration mineral assemblages. Stable fluid chemistries produced in these and other dilute-water/whole-rock experiments (80 °-300 ° C) were then compared with reservoir data from several geothermal fields. The comparisons show that experiments of this type can reproduce many properties of geothermal reservoir fluids. Like geothermal fluids, compositional parameters (pH, cation/proton ratios, cation/cation ratios, and neutral species concentrations) for species in experimentally derived fluids are temperature dependent but are relatively independent of rock, water, and water/rock mass ratio. At lower temperatures (less than or equal to 250° C), many of these experimental parameter-temperature trends agree with geothermal trends. However, at higher temperatures ( greater than or equal to 250° C), the geothermal fluids have calculated high-temperature pH values 1 to 2 pH units lower than do the experimentally-derived fluids. This produces a consistent offset between values of experimental and natural cation/proton activity ratios. Possible causes for the offsets include: pervasive metastable mineral formation in experiments; and absence, in experiments, of the equivalent of a magmatic or metamorphic gas input. Results from modified water/rock experiments indicate that, while metastability may be a partial cause for the offsets, geothermal fluid parameters can be duplicated by addition of CO2. Furthermore, maintenance of high /CO2, low pH conditions required a CO2 flux. Magmatic gas flux is not always considered in chemical models of geothermal systems and its requirement in the experiments may indicate that E CO2 should be taken as an independent variable. Finally, comparable offsets could also be caused by the addition of exotic co2 or other acid gases during upflow or sampling of wet steam discharges. Field influences such as these would give rise to lower than actual reservoir pH's. Thus the offsets could indicate that some geothermal fluid pH's are more basic than commonly calculated and closer to those attained in water/rock experiments. Water/rock experiments are capable of simulating many of the chemical features of geothermal reservoir fluids but interpretation of experimental data is not straightforward. The closed-system and relatively short-term nature of the experiments must be considered when making comparisons with natural phenomena. Of equal importance is a clear understanding of the natural phenomena being modeled.

Download or read book Simulation of Steam Transport in Vapor dominated Geothermal Reservoirs written by Geological Survey (U.S.) and published by . This book was released on 1976 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fluid Inclusion Stratigraphy written by Lorie M. Dilley and published by . This book was released on 2007 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book U S Gulf Coast Geopressured geothermal Reservoir Simulation written by R. C. MacDonald and published by . This book was released on 1982 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book U S Gulf Coast Geopressured Geothermal Reservoir Simulation written by R. M. Knapp and published by . This book was released on 1985 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book U S Gulf Coast Geopressured Geothermal Reservoir Simulation written by S. K. Garg and published by . This book was released on 1977 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book U S Gulf Coast geopressured geothermal reservoir simulation written by R. M. Knapp and published by . This book was released on 198? with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book U S Gulf Coast Geopressured Geothermal Reservoir Simulation written by and published by . This book was released on 1979 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book US Gulf Coast Geopressured geothermal Reservoir Simulation Final Report Year 3 written by and published by . This book was released on 1981* with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several reservoir model improvements incorporated into the UTA model are described. The most significant modification to the model was the inclusion of semiimplicit treatment of transmissibilities so as to better handle two-phase flow problems associated with flow near the wellbore. A description of the reservoir mechanics presumed operative in geopressured-geothermal reservoirs is included. A mathematical model describing two-dimensional flow in compacting porous media is developed from the Lagrangian point of view. A description of the way the differential equations are approximated by finite differences and subsequently solved by means of numerical procedures is presented. Various sensitivity studies made with the reservoir model are described. Particular emphasis was given to the study of potential shale dewatering effects on reservoir depletion and the effects of compaction on fluid recovery. To study shale dewatering, the shale thickness and the shale vertical permeability were treated as variables in several simulation experiments. The effects of compaction were modeled with optimistic and pessimistic values for the uniaxial compaction coefficient in an attempt to define a region of expected reservoir performance. Laboratory analysis of core samples obtained from the geopressured-geothermal test well was completed by the end of year 3. These data indicate that the uniaxial compaction coefficient is of the same order of magnitude as the pessimistic value used on the sensitivity studies. Because of this the expected fluid recovery from geopressured reservoirs has been reduced to a nominal 5% of the in-place volumes rather than the previously reported 10%.

Download or read book Modeling Brine rock Interactions in an Enhanced Geothermal Systemdeep Fractured Reservoir at Soultz Sous Forets France written by Karsten Pruess and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The modeling of coupled thermal, hydrological, and chemical (THC) processes in geothermal systems is complicated by reservoir conditions such as high temperatures, elevated pressures and sometimes the high salinity of the formation fluid. Coupled THC models have been developed and applied to the study of enhanced geothermal systems (EGS) to forecast the long-term evolution of reservoir properties and to determine how fluid circulation within a fractured reservoir can modify its rock properties. In this study, two simulators, FRACHEM and TOUGHREACT, specifically developed to investigate EGS, were applied to model the same geothermal reservoir and to forecast reservoir evolution using their respective thermodynamic and kinetic input data. First, we report the specifics of each of these two codes regarding the calculation of activity coefficients, equilibrium constants and mineral reaction rates. Comparisons of simulation results are then made for a Soultz-type geothermal fluid (ionic strength {approx}1.8 molal), with a recent (unreleased) version of TOUGHREACT using either an extended Debye-Hueckel or Pitzer model for calculating activity coefficients, and FRACHEM using the Pitzer model as well. Despite somewhat different calculation approaches and methodologies, we observe a reasonably good agreement for most of the investigated factors. Differences in the calculation schemes typically produce less difference in model outputs than differences in input thermodynamic and kinetic data, with model results being particularly sensitive to differences in ion-interaction parameters for activity coefficient models. Differences in input thermodynamic equilibrium constants, activity coefficients, and kinetics data yield differences in calculated pH and in predicted mineral precipitation behavior and reservoir-porosity evolution. When numerically cooling a Soultz-type geothermal fluid from 200 C (initially equilibrated with calcite at pH 4.9) to 20 C and suppressing mineral precipitation, pH values calculated with FRACHEM and TOUGHREACT/Debye-Hueckel decrease by up to half a pH unit, whereas pH values calculated with TOUGHREACT/Pitzer increase by a similar amount. As a result of these differences, calcite solubilities computed using the Pitzer formalism (the more accurate approach) are up to about 1.5 orders of magnitude lower. Because of differences in Pitzer ion-interaction parameters, the calcite solubility computed with TOUGHREACT/Pitzer is also typically about 0.5 orders of magnitude lower than that computed with FRACHEM, with the latter expected to be most accurate. In a second part of this investigation, both models were applied to model the evolution of a Soultz-type geothermal reservoir under high pressure and temperature conditions. By specifying initial conditions reflecting a reservoir fluid saturated with respect to calcite (a reasonable assumption based on field data), we found that THC reservoir simulations with the three models yield similar results, including similar trends and amounts of reservoir porosity decrease over time, thus pointing to the importance of model conceptualization. This study also highlights the critical effect of input thermodynamic data on the results of reactive transport simulations, most particularly for systems involving brines.

Download or read book Gulf Coast Geopressured geothermal Reservoir Simulation written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of the short-term production tests run on the Pleasant Bayou No. 2 well are summarized. These tests were analyzed using conventional pressure test analysis methods. The effects of reservoir heterogeneties onm production behavior and, in particular, permeability distribution and faulting of reservoir sand were studied to determine the sensitivity of recovery to these parameters. A study on the effect of gas buildup around a producing well is reported. (MHR).

Download or read book Rock water Interactions in Hot Dry Rock Geothermal Systems written by Charles Owen Grigsby and published by . This book was released on 1983 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: