The experimental study of the water-rock interaction shows that the secondary mineral assemblage depends on the water composition. For example, granite-pure water interaction produces zeolites (relatively low-dense, Mg-poor minerals), whereas seawater yields chlorites (high-dense, Mg-rich minerals). The reactions have volumetric effects from several % to 20 % in magnitude. Volume deformations in the heterogeneous matrix cause uneven mechanical strains. Reactions with the effect of about 0,1 vol.% may cause strains of the order of 100-1000 bars being enough for destruction of rocks. Signs and magnitudes of local volume changes depend on the mineral composition of the secondary assemblage. Hence, one can provide either healing or cracking of primary fractures, as desired, by changing the composition of water in the water-felsic rock system where some elements (Mg, Fe) are in lack. The techniques of "chemical hydrofracturing" looks promising as applied to a granite HDR massif. One can regulate the permeability of fractured flow paths by changing in concord the composition and pressure of the injected water. This approach should promote efficient extraction of the petrothermal energy.

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.

A weekly publication, the Texas Register serves as the journal of state agency rulemaking for Texas. Information published in the Texas Register includes proposed, adopted, withdrawn and emergency rule actions, notices of state agency review of agency rules, governor's appointments, attorney general opinions, and miscellaneous documents such as requests for proposals. After adoption, these rulemaking actions are codified into the Texas Administrative Code.

Letter opinion issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Dan Morales, regarding a legal question submitted for clarification; Whether various testing communities or other entities that approve the contents of a licensing examination may meet in executive session to discuss test questions and answers (ID# 36466)

Letter opinion issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Dan Morales, regarding a legal question submitted for clarification; Whether the offense of criminal trespass, Penal Code section 30.05, may be committed on a bus (ID# 37779)

Letter opinion issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Dan Morales, regarding a legal question submitted for clarification; Whether the district and statutory county courts of Brazos County may utilize a centralized filing system for misdemeanor cases, so that the county attorney may file a misdemeanor case to be tried in either the district or a statutory county court with the county clerk (ID# 37938)

Letter opinion issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Dan Morales, regarding a legal question submitted for clarification; Whether a municipality utility district board member becomes ineligible to serve on the board if during the board member's term he or she no longer owns property in the district or is no longer a registrated voter in the district (ID# 38145)

Letter opinion issued by the Office of the Attorney General of Texas in Austin, Texas, providing an interpretation of Texas law. It provides the opinion of the Texas Attorney General, Dan Morales, regarding a legal question submitted for clarification; Whether a church is entitled to an exemption from ad valorem taxes on property that it purchases in the middle of the tax year (ID# 36358)

We demonstrate that there are regions of parameter space in the next-to-minimal (i.e. two-Higgs-doublet, one-Higgs-singlet superfield) supersymmetric extension of the SM for which none of the Higgs bosons are observable either at LEP2 with $\sqrt{s}=192 GeV$ and an integrated luminosity of $L=1000inverse pb$ or at the LHC with $L=600 inverse fb$.

Well SN-12 in the Seltjarnarnes low-temperature field in SW-Iceland was drilled to a depth of 2714 m in the fall of 1994. The well appeared to be almost non-productive at the end of drilling. A comprehensive ten day stimulation program was, therefore, initiated. The program involved, firstly, high-pressure wellhead injection and, secondly, high-pressure injection below a packer placed at 1412 m depth. After about twelve hours of wellhead stimulation the pressure dropped suddenly, indicating that the well had been stimulated. At the same time the water level response increased suddenly in two near-by monitoring wells. During the second stimulation phase (packer at 1412 m) the well appeared to be stimulated even further. The well eventually produced about 35 l/s with a drawdown of roughly 60 m, and the stimulation had increased the yield of the well by a factor of nearly 60. Thus well SN-12, which appeared to be almost non-productive at the completion of drilling, had turned into a good production well. It is believed that during the stimulation some previously closed fractures, or interbed contacts, reopened connecting well SN-12 to the main fracture system of the geothermal reservoir.

High-temperature hydrothermal systems are physically and chemically zoned with depth. The energy input is from a magmatic zone, intruded by igneous bodies, that may also contribute variable amounts of magmatic fluid to the system. The heat source is directly overlain by a section of rocks, that due to their elevated temperature, respond to stress in a ductile fashion. The ductile zone is, in turn, overlain by a section of rocks that respond to stress in a brittle fashion, where water is able to circulate through fractures (the geothermal reservoir) and will be termed the hydrothermal circulation zone. Ancient and modern high-temperature geothermal systems show a predictable sequence of evolutionary events affecting these stratified zones. Metamorphic core complexes are uplifts, formed in highly extended terrains, that expose fossil brittle-ductile transition zones. Formerly ductile rocks have had brittle fractures superimposed on them, and meteoric hydrothermal systems are associated with the brittle fracturing. Porphyry copper deposits typically evolve from magmatic to meteoric hydrothermal systems. At the Larderello geothermal system, the brittle- ductile transition has been mapped using reflection seismology, and the zone has been penetrated by the San Pompeo 2 well where temperatures >420°C were encountered. Although neo-granitic dikes have been penetrated by …

Well AH-4_bis, at the Ahuachapan Geothermal Field is planned to be drilled on the same pad as the former AH-4. A simulation study was carried out for two casing dameters 13 5/8 and 9 5/8” in order to estimate its production and to know its economic feasibility. The simulation results indcate a high probability of production in the range of 7 Mwe, equivalent to 120 kg/s total mass flow rate, 1250 kJ/kg at 6 bar-a for the new well AH-4_bis. Well AH- 17 is good producer, during 1991 after ten years of production, the well was shut-in due to silica scaling problems. A wellbore simulation was carried out in order to predict the new production conditions after the work-over, mainly to estimate the water flow rate in order to reduce the silica scaling. The results indicate a very low water flow rate. The match between the simulated and measured production curves after the work-over was successful. The well AH-18 is located at the southern part of the actual bore field. CEL is planning to expand the borefield at this area and it is neccessary to estimate the possible production condtions at that zone. The results indicate a high probabilty of …

Previous measurements of acoustic velocities on NEGU- 17 cores indicate that saturation effects are significant enough to cause V_p/V_s anomalies observed in the field. In this study we report on the results of new measurements on core recently recovered from SB-15-D along with some additional measurements on the NEGU-17 cores. The measurements indicate correlations between mechanical, transport, and water storage properties of the matrix which may prove useful for reservoir assessment and management. The SB-15-D material is found to be similar to the NEGU-17 material in terms of acoustic velocities, being characterized by a notably weak pressure dependence on the velocities and a modest V_p/V_s signature of saturation. The effect of saturation on V_p/V_s appears to result in part from a chemo-mechanical weakening of the shear modulus due to the presence of water. Electrical properties of SB-15-D material are qualitatively similar to those of the NEGU-17 cores, although resistivities of SB-15-D cores are notably lower and dielectric permittivities higher than in their NEGU- 17 counterparts. While some limited correlations of measured properties with depth are noted, no clear change in character is observed within SB-15-D cores which can be associated with the proposed cap-rock/reservoir boundary.

A numerical simulation model for the Heber geothermal field in Southern California is being developed under a technology transfer agreement between the Department of Energy/Lawrence Berkeley National Laboratory (LBNL) and the California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR). The main objectives of the cooperation are (1) to train DOGGR personnel in the use of the TOUGH2PC computer code; and (2) to develop a module compatible with TOUGH2 to investigate the effects of production/injection operations on the ground surface subsidence-rebound phenomenon observed in the Heber geothermal field. Initial-state calibration (undisturbed system) runs are being conducted to calibrate the model.

Downhole temperature and pressure, mass flow, and enthalpy measurements on three production wells at Kawerau geothermal field are interpretted to illustrate interference effects between these wells. Feed zone locations within the wells, together with geology and chemistry are discussed. Downhole measurements are made in one well while production flow changes are made on another well to monitor pressure transient effects. The interference effects have implications for planning future production drilling.

This paper describes the design, construction, and preliminary results of an experiment that studies imbibition displacement in two fracture blocks. Three core configurations were constructed. The configurations are a compact core, a two-block system with a 1 mm spacer between the blocks, and a two-block system with no spacer. The blocks are sealed in epoxy so that saturation measurements can be made throughout the displacement experiments using a Computed Tomography (CT) scanner. Preliminary results are presented from a water/air experiment. These results suggest that it is incorrect to assume negligible capillary continuity between matrix blocks as is often done.

The Tiwi geothermal field is located in southern Luzon on the northeast flank of Mt. Malinao, an andesitic volcano that was active 0.5 to 0.06 Ma. Matalibong-25 (Mat-25) was drilled through the Tiwi reservoir to investigate lithologic and fracture controls on reservoir permeability and to monitor reservoir pressure. Continuous core was collected from 2586.5 to 8000 feet (789 to 2439 meters) with greater than 95% recovery. The reservoir rocks observed in Mat-25 consist mainly of andesitic and basaltic lavas and volcaniclastic rocks above 6600 feet depth (2012 meters) and andesitic sediments below, with a transition from subaerial to subaqueous (marine) deposition at 5250 feet (1601 meters). The rocks in the reservoir interval are strongly altered and veined. Common secondary minerals include chlorite, illite, quartz, calcite, pyrite, epidote, anhydrite, adularia and wairakite. An ³⁹Ar/⁴⁰Ar age obtained on adularia from a quartz-adularia-cemented breccia at a depth of 6066 feet (2012 meters) indicates that the hydrothermal system has been active for at least 320,000 years. Fractures observed in the core were classified as either veins (sealed) or open fractures, with the latter assumed to represent fluid entries in the geothermal system. Since the core was not oriented, only fracture frequency and dip angle …

A closed-loop circulation test was conducted from 10 May to 14 July 1995 on the Hot Dry Rock (HDR) reservoir at Fenton Hill, New Mexico after a hiatus of nearly two years. Changes in heat transfer and reservoir volume were investigated and compared to previous circulation tests. Chemical tracers can be used to measure the volume of flow paths in hydrologic systems. Usually, tracers are used in low temperature situations, but the application to high temperature systems has been established for certain tracer compounds. During the 1995 flow testing at Fenton Hill, both a conservative and a non conservative tracer were injected into the reservoir in each of two separate experiments. The purpose was to determine the volume of the most direct flow paths and to estimate the total volume of fractures in the system. The results indicate a relatively static reservoir volume between June and July, yet with an increase in flow dispersion. It can be assumed that channeling of flow did not occur in the main body of the reservoir due to continuous operation. However, a new flow path adjacent to the injection well did develop, and its affect on reservoir flow was investigated using tracer technology. The …

Core flooding experiments on argillaceous sandstone are carried out showing that for high injection flow rates permeability reduction occurs. The decrease of permeability is a consequence of the migration of insitu particles. Two models are used to simulate the observed phenomena. The so-called network model is able to give insight in the physics behind the particle migration. The other model based on mass balance and constitutive laws is used for quantitative and qualitative comparison with the experiments.

We report on continuing experimental and numerical efforts to obtain steam-water relative permeability functions and to assess effect of heat transfer and phase change. To achieve these, two sets of steady-state flow experiments were conducted: one with nitrogen and water and another with steam and water. During these experiments, a mixture of nitrogen-water (or steam-water) was injected into a Berea sandstone core. At the onset of steady state conditions, three-dimensional saturation distributions were obtained by using a high resolution X-ray computer tomography scanner. By identifying a length of the core over which a flat saturation profile exists and measuring the pressure gradient associated with this length, we calculated relative permeabilities for nitrogen-water flow experiments. The relative permeability relations obtained in this case were in good agreement with those reported by other investigators. Another attempt was also made to conduct a steam-water flow experiment under adiabatic conditions. This experiment was completed with partial success due to the difficulties encountered during the experiment. The results of this experiment showed that a flat saturation profile actually developed over a substantial length of the core even at a comparatively modest injection rate (6 grams per minute) with low steam quality (4% by mass). The …

Theoretical calculations have been performed to estimate the electrical generating capacities of small-diameter geothermal wells for off-grid rural electrification using wellhead generators. In these applications, generating capacities of interest are typically in the range 100-1000 kWe. The approach amounted to (1) calculating the “wellhead discharge characteristics” (water/steam discharge rates as functions of wellhead pressure) for a variety of hypothetical well and reservoir descriptions, (2) employing a mathematical representation for the net generating capacity of a wellhead powerplant as a function of its operating inlet pressure and steam inlet rate, and (3) varying the wellhead (= turbine inlet) pressure to identify the “optimum” pressure value at which the net electrical power is maximized. Calculations were carried out for well diameters from 75 mm to 300 mm, for well depths from 300 to 1200 meters, for reservoir temperatures from 100°C to 240°C, for piezometric surface depths (related to shut-in reservoir pressure) from zero to 250 meters, and for downhole productivity indices from 2 kg/s/bar to infinity. A few cases were also included in which the CO₂ content of the reservoir fluid was non-zero (up to 1% by mass in the brine). Both backpressure and condensing single-flash steam turbine powerplants were considered. The …

A solid waste is classified as hazardous if it contains sufficient leachable components to contaminate the groundwater and the environment if disposed in a landfill. Scale, sludge and drilling mud from three geothermal fields (Bulalo, Phlippines; Cerro Prieto, Mexico; and Dixie Valley, USA) containing regulated elements at levels above the earth‘s crustal abundance were studied for their leachability. Cr, As, Cu, Zn and Pb were detected at levels which could impair groundwater quality if leaching occurred. Several procedures were used to assess the likely risk posed by the residues : protocol leaching tests (Canadian LEP and US TCLP), toxicity testing, accelerated weathering test, and a preliminary acid mine drainage potential test. Whole rock analysis, X-ray diffraction, and radioactivity counting were also performed to characterize the samples. Toxi-chromotest and SOS-chromotest results were negative for all samples. Leachng tests indicated that all of them could be classified as nonhazardous wastes. Only one of the six showed a low-level radioactivity based on its high Pb-210 activity. Initial tests for acidification potential gave positive results for three out of six samples whle none of the regulated elements were found in the leachate after accelerated weathering experiment for three months.