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SYNOPSIS: Modified water loss tests are proposed to improve the knowledge of water flow in rock discontinuities. Laboratory tests were performed in three types of rock fractures with varying surface roughness to analyse the nature of flow in rock discontinuities. Field and laboratory test results were compared. The concept of "equivalent opening" is introduced for flow prediction and analysis. RESUME: L'etude de la percolation d'eau dans des massifs rocheux nous a amenes à la proposition d'une amelioration des essais du type Lugeon. Des'essais en laboratoire ont ete effectues sur trois types de fractures avec des rugosites differentes. La comparaison des resultats des essais en laboratoire avec les resultats des essais in situ a permis de formuler le concept d" ouverture equivalente". ZUSAMMENFASSUNG: Wir schlagen verschiedene Wasserverlustteste vor, um das Verstandnis von Wasserfluß in Felsbruechen zu verbessern. Laboratorium- Tests wurden an drei verschiedenen Arten von Felsbruechen mit verschiedener Oberflachenrauhheit durchgefuehrt, um die Art des Flusses im Felsbruch zu bestimmen. Feld- und Laboratorium-Testergebnisse wurden verglichen. Wir fuehren den Begriff der "Aquivalenten Durchlassigkeit" fuer Flußvorhersage und -analyse ein. 1- MODIFIED WATER PRESSURE TEST To investigate flow characteristics in a rock discontinuity at the site of' Nova Avanhandava dam, in Sāo Paulo, Brasil, six tests were performed using a modified procedure that includes several stages of pressure both on loading and unloading cycles. At the begining tests were performed with very low pressure stages, including infiltration tests to make possible the analysis of a complete curve relating flow with effective head. Typical tests results, are shown in Figs. 1 and 2. The same results can be reploted as in Fig. 3 and 4 relating flow over effective head versus effective head. The non linearity of relation of flow to effective head is indicative of flow regimen, that should start as linear for very low pressures passing by a transitory regimen and leading to a turbulent flow. Tables 1 and 2 shows the traditional water loss coefficient for laminar flow and the modified water loss coefficient for turbulent flow. These tables already includes an evaluation of opening of the joint using concepts of laminar and turbulent flow. The relationship of water loss coeficcient (WLC) to equivalent opening could be obtained from Fig,5, considering that only one joint was involved within the tests and using conventional well formulae (Cruz, 1979). 2- LABORATORY TESTS In order to understand the nature of flow in rock discontinuities, hydraulic conductivity tests were performed on a very simple device using 2" samples, 30 cm in length and varying both the opening as well as the rugosity of the rock surfaces. Typical test results are shown in Figs.6, 7 and 8, relating flow with gradient (Quadros, 1982). The same non linearity of flow versus pressure (gradient) is obtained. In order to simulate a field water pressure test, laboratory test results had to be transformed in relations of flow versus effective head. In the laboratory test flow develops on a rectangular section of approximately constant width, as shown in Fig. 9 (Quadros, 1982). In a field water pressure test the flow is radial and in increasing areas. Fig. 10 shows the assumed radial distribution of flow. Considering the above model and the empirical equations derived from regression analysis relating unit flow (q), gradient (J), opening (e) and absolute rugosity (k), diagrams relating flow with effective pressure were prepared for the three types of rock surfaces tested on the laboratory. Fig. 11 shows test results for the smooth surface and Fig. 12 the test results for the three rock surfaces tested at the same opening (0,7 mm). It is evident from the last figure the influence of the rock surface rugosity on the amount of flow for the same gradient (or the effective head). 3- COMPARISON OF FIELD AND LABORATORY TESTS Superimposing the field data on-laboratory tests results with the same type of relation we can see that an "equivalent opening" for field discontinuity of 0,60 to 0,70 mm gives the best agreement between tests if we consider a smooth surface but for a rough surface the best agreement is reached with an "equivalent opening" of about 0,80 to 1,0 mm. The test results shows a non linear relation of flow versus effective head, suggesting a transitory to turbulent flow. A comparison between this value and, those ones listed on Tables 1 and 2 shows, "that for test "in Borehole nọ 126 C-III an "equivalent opening" of 0,70,to 0,80,mm is obtained and for borehole nọ 102 C-III a value of e varying from 0,70 to 0,10 mm for turbulent flow(see Fig. 5) corresponds to the best agreement. It is important to observe that the "equivalent opening" for laminar flow is much smaller. Rugosity is an important factor, because the head losses are increased. The "equivalent opening" reflects the effective area where the water flows.
- Research Report > New Finding (0.54)
- Research Report > Experimental Study (0.54)
ZUSAMMENFASSUNG: Ein ueberarbeitetes Konzept des Wasserabpreßversuches wird vorgestellt. Änderungen zum herkömmlichen Verfahren bestehen bei der Versuchsapparatur, der Versuchsdurchfuehrung und der Versuchsauswertung. Verbesserungen der Meßgenauigkeit ergeben sich durch die Verwendung elektrischer Druckaufnehmer im Verpreßsegment des Bohrloches und induktiver Durchflußmengenmesser sowie analoger Meọdatenerfassung oder gleichwertiger digitaler Verfahren. Die Versuchssteuerung ueber eine konstante Verpreßmenge mit zeitaquivalenten Pausen zwischen den Verpreßstufen ermöglicht die Durchlassigkeitsbestimmung mit Verfahren, die den tatsachlich vorliegenden instationaren Strömungsbedingungen entsprechen. SYNOPSIS: A revised concept of the water pressure test is being presented. Compared with the conventional procedure, the testing apparatus, procedure and assessment have all been altered. The accuracy of measurement is improved by the use of electrical pressure sensors in the pressure segment of the drilling hole, the use of inductive flow-meters, as well as the recording of measuring data by analog or digital processes of identical accuracy. The control of the experiment by means of a constant quantity under pressure and intervals of equal time between the various stages of the pressure test make it possible to determine the porosity through processes which correspond in fact to the actual flow conditions. RESUME: On presente un concept modifie de l'essai de Lugeon. Le dispositif et le protocole des tests ainsi que l'evaluation des resultats ont tous ete modifies par rapport au procede courant. La precision des mesures est amelioree grace à l'emploi des sondes de pression electriques inserees dans le segment de pression du trou de forage et d'appareils de mesure d'ecoulement inductifs ainsi que par l'enregistrement de donnees de mesure par des calculateurs analogues ou numeriques de precision identique. Le contrôle des experiences est rendu possible grace à une quantite d'eau constante sous pression appliquee à des intervalles de temps egaux aux divers stades de l'essai, ce qui permet de preciser la porosite par des processus qui correspondent aux conditions d'ecoulement reelles. EINFÜHRUNG Der Wasserabpreßversueh gehört im Felsbau immer noch zu den gebrauehliehsten Versuehsverfahren, da er einfaeh in der Durehfuehrung ist, keine langen Versuchszeiten benötigt und keine aufwendige Versuehsapparatur beansprucht. Diese Versuchsmethode wird heute sowohl zur Durehlassigkeitspruefung des Gebirges als auch zur Planung und Pruefung von Injektionsarbeiten verwendet. In seiner herkömmlichen Form birgt der Wasserabpreßversuch eine Reihe von systematischen Fehlern, die zu groben Fehlinterpretationen der Ergebnisse fuehren. Diese lassen sich durch eine Änderung des apparativen Aufbaus, der Durchfuehrung und der Auswertung des Versuehs korrigieren. Aufgrund der Komplexitat der Strömungsvorgange im Fels ergeben sich außerdem eine Reihe von problemen, die bei der Durchfuehrung und Auswertung besonders zu beruecksichtigen sind. Die Wasserfuehrung im Fels findet in der Regel in drei Systemen statt - dem Gestein, den Klueften und Störungen. Diese unterscheiden sich in ihren Durchlassigkeitseigenschaften stark voneinander (Abb.1). Einzelne Singularitaten wie Großkluefte oder Störungszonen können die Durchlassigkeit ganzer Gebirgsbereiehe dominieren. Bei der begrenzten Reichweite des Wasserabpreßversuchs kann weiterhin der Fall eintreten, daß eine statistische Regelung des Kluftgebirges in dem untersuchten Gebirgsbereich nicht vorliegt und somit das Versuehsergebnis nur die Durchlassigkeit einzelner Kluftindividuen weitergibt. Die Kenntnis ueber die Beschaffenheit des Kluftgefueges ist deshalb eine wesentliehe Voraussetzung fuer eine folgerichtige Durchfuehrung und Auswertung der Versuche. Die Ermittlung der Durchlassigkeit kann sowohl fuer-einzelne Kluefte als auch fuer quasi homogenes Gebirge nach dem diskontinuierliehen bzw. nach dem kontinuierlichen Durchlassigkeitsmodell erfolgen (WITTKE 1970). Da jedoch analytische Lösungen fuer die diskontinuierliehe Durchlassigkeit auf einfache Falle beschrankt sind (RISSLER 1977), muß die Versuchsauswertung ohne numerisehe Hilfsmittel ueberwiegend nach dem kontinuierlichen Modell erfolgen. Das nachfolgend vorgestellte Versuchskonzept des Wasserabpreßversuches dient zur Bestimmung der durchschnittlichen Durchlassigkeit und zur Pruefung der Injizierbarkeit von Fels. Der Versuch kann sowoh1 a1s Einbohrlochversuch wie als Mehrbohrlochversuch durchgefuehrt werden. Zur Ermittlung der Durchlaissigkeit wird vorausgesetzt, daß die Verpreßstelle unterhalb des Grundwasserspiegels liegt, die Stàrung rechtwinklig zum Bohrloch verlauft, der Aquifer gespannt ist und instationare Strömungsbedingungen vorliegen. 2. VERSUCHSAPPARATUR Die Versuchsapparatur besteht aus einer Wasserpumpe mit Tank, einem Durchflußmengenmeßgerat, einem Absperrschieber am Bohrlochkopf, einem Doppelpackersystem und einer Meßsonde. Im Mehrbohrlochversuch sind weitere Packersysteme und Sonden erforderlich (Abb. 2). Die Dichtung des Verpreßsegments erfolgt mit einem Doppel- oder Mehrfachpacker. Pneumatische Packer haben sich zur Dichtung des Verpreßsegments in der Injektionsbohrung durch ihre Fahigkeit sich den Unebecheiten der Bohrlochwandung anzupassen, besonders bewahrt. Die Manschettenlange der Packer sollte 0,6 m nicht unterschreiten, größere Langen bis zu 1,5 m gewahren grössere Dichtungserfolge. Die Abdichtung der Segmente in den Beobachtungsbohrungen erfolgt in derselben Weise. Im Verpreßsegment und in den Beobachtungssegmenten ist eine Meßsonde zur Beobachtung des Verpreßdruckes bzw. Bergwasserdrucks erforderlich. Die Messung erfolgt mit elektrischen Druckaufnehmern. Die Verpressung wird mit einer mechanisch regelbaren Pumpe vorgenommen, die eine konstante Mengenförderung im Bereich von ca. 1 - 150 l/min erlaubt. Am Bohrlochkopf ist eine Schließvorrichtung mittels Schieber erforderlich. Die Versuchsdaten sind kontinuierlich und lueckenlos zu erfassen. Hierzu kann entweder eine analoge Aufzeichnung ueber einen Mehrkanalschreiber mit Parameter-Zeitachsenregistrierung oder eine elektronische Datenerfassungsanlage mit digitaler Registrierung verwendet werden. Bei letzterer sollten die Zeitabstande zwischen den einzelnen Messungen 0,5 Sekunden nicht ueberschreiten.
SYNOPSIS: Analysis of stresses around a sand arch shows that a failure criterion exists. When a critical flow rate is reached the arch will collapse, leaving behind a greater cavity. Field test data can consistently be described by this theory. Extending the stress analysis to cylindrical wellbores shows that a plastically strained zone develops in poorly cemented rocks, when the well is drilled. During production this zone increases with the flow rate until the entire layer is fluidized. When injecting, fracture conditions may be reached before the material returns to an elastic state of stress. The stress analysis can be used to estimate the strength of the rock near the wellbore. RESUME: L'analyse des contraintes autour d'une arche de sable montre l'existence d'une condition de stabilite critique. Quand le debit de fluide atteint un niveau maximum, l'arche s'ecroule, provoquant une plus grande cavite. Cette theorie est verifiee par des resultats d'essais effectues sur un puits reel. L'extension de cette analyse à un trou cylindrique montre que l'on aura une zone plastiquement deforme autour du puits quand on fore dans une formation mal cimentee. En production cette zone croît avec le debit jusqu'à ce que la formation entière s'ecoule comme un fluide. En injection les conditions de fracturation peuvent être atteintes avant que la formation ne soit revenue à l'etat elastique. Cette theorie peut aussi être utilisee pour obtenir indirectement une valeur de la resistance de la roche autour du puits. ZUSAMMENFASSUNG: Die Analyse von Spannungen um ein Gewölbe aus Sand zeigt, daß ein Bruchkriterium existiert. Wenn eine kritische Strömungsrate erreicht ist, bricht das Gewölbe und hinterlaßt einen größeren Hohlraum. Feldtestdaten können mit dieser Theorie widerspruchsfrei beschrieben werden. Wendet man die Spannungsanalyse auf zylindrische Bohrlêcher an, dann zeigt sich, daß in schlecht zementiertem Gestein eine plastisch deformierte Zone entsteht, wenn der Brunnen gebohrt wird. Wahrend der Produktionsphase erweitert sich diese Zone entsprechend der Strömungsrate, bis die gesamte Schicht verfluessigt ist. Bei Injektion können die Bruchbedingungen erreicht werden, bevor das Material wieder zu einem elastischen Spannungszustand zurueckgekehrt ist. Die Spannungsanalyse kann genutzt werden, um die Festigkeit des Gesteins in Bohrlochnahe abzuschatzen. INTRODUCTION The purpose of drilling a well in petroleum exploration is to locate and produce hydrocarbons on a commercial basis. Before the drill penetrates the down hole strata, there will be horizontal and vertical stresses, caused by the weight of the overlying strata and tectonic activity. As the drilling bit makes the hole, the vertical and horizontal stresses will be changed around the wellbore. This paper describes stress analyses performed on a poorly consolidated layer of rock around a well. The main purpose of this work, when it started several years ago, was to investigate the sand problem occurring in poorly consolidated sandstones when oil and gas is produced. Recently, a more general stability analysis has been made and this analysis has also served as a basis for the investigation of hydraulic fracture initiation pressures. The sand problem is normally experienced as sand influx from the formation into the production string. Flow of formation fines together with the produced fluids is often experienced during normal production. Such particle flow will not be a serious problem because the particles are small and small in quantity. Particle flow starts to be a real problem only when load bearing grains are removed from the formation, which will result in a reduction in the load carrying capacity and a potential failure of the formation. Formation of sand arches behind perforation openings is a mechanism that can stabilize a poorly consolidated sand and prevent it from flowing into the well. Sand stability by arching was first treated by Terzaghi (1936) in his trap door experiment, demonstrating that arching was a real and stable phenomenon. Later Hall and Harrisberger (1970) made an experimental study on arches in relation to maximum sand free production rates. Stein et al. (1974) and Stein (1977) assumed that the maximum flow rate an arch can withstand is proportional to the shear modulus G for the sand. The G modulus they obtained from accoustic and density logging data. Tippie and Kohlhaas (1974) and Cleary et al. (1979) made laboratory studies of the arching phenomenon and its relation to flow rate and confining stress levels. Tixier et al. (1974) treated the prediction of sanding from an interpretation of the mechanical properties log. Coates and Denoo (1981) introduced a refinement of the method presented by Tixier et al. Typical for these works is that they are based on empirical relations derived from experimental data and field operations. A theoretical study of the stresses around a sand arch, supported by laboratory work, has been made by Bratli and Risnes (1981). The laboratory investigation showed there existed a limit to the load imposed by the. fluid drag forces that a given arch can sustain.
SYNOPSIS: This paper describes a thermo mechanical numerical analysis of four potential nuclear waste repositories in salt in the Unite States: Paradox Basin, Utah; Permian Basin, Texas; Richton Dome, Mississippi; and Vacherie Dome, Louisiana. The analysis considers the region encompassing the disposal room. Thermo mechanical responses are compared to help assess the suitability of each site as a nuclear waste repository. RESUME: Cette communication decrit une analyse numerique thermomecanique de quatre depôts eventuels pour les residus nucleaires dans des formations salifères aux Etats-Unis, à savoir: Paradox Basin, Utah; Permian Basin, Texas; Richton Dome, Mississippi; et Vacherie Dome, Louisiana: L'analyse concerne la zone qui entoure la chambre d'isolation. On compare les reponses thermomecaniques afin d'etablir l'ordre de choix relatif de chaque emplacement comme depôt pour les residus nucleaires. ZUSAMMENFASSUNG: Die Studie beschreibt eine thermomechanische numerische Analyse der vier potentiellen Endlager fuer radioaktiven Abfall im Salz in den U.S.A.: Paradox Basin, Utah; Permian Basin, Texas; Richton Dome, Mississippi; and Vacherie Dome, Louisiana. Die Analyse bezieht sich auf die nahere Umgebung der Ein1agerungsstrecke. Die thermomechanischen Auswirkungen werden verglichen, um die Eignung jedes Standortes fuer ein Endlager fuer radioaktiven Abfall beurteilen zu können. 1. INTRODUCTION 1.1 Background The development of nuclear energy has created a need for the safe disposal of radioactive wastes. In the United States, the, National Waste Terminal Storage (NWTS) Program has been established to determine suitable repository sites in deep geologic formations that will provide a safe barrier between the disposed commercial nuclear wastes and the surface environment. Salt is a primary candidate to host a nuclear waste repository because it has a relatively high thermal conductivity, is relatively free of water, and is a ductile material that can undergo large deformations without failing. Currently, four salt formations are being considered as potential sites for a nuclear waste repository. Two of these formations are domal salts (Richton Dome in Mississippi and Vacherie Dome in Louisiana) and two are bedded salts (Paradox Basin in Utah and the Permian Basin in Texas). 1.2 Objectives. The objectives of this study are two fold, viz:Compare the thermal and thermomechanical responses of the four potential nuclear waste repository sites in salt. Provide predictions of thermal and thermomechanical responses at each of the four sites which will assist in the repository design process. The first and primary objective pertains to thermal and thermomechanical considerations which constitute a part of the selection process for a repository site. In the comparison, of the four sites, the predicted temperatures and deformations are considered at strategic locations within the disposal room region. The secondary objective of this study provides a unique opportunity to, evaluate "site-specific" repository conditions. This extensive data report discusses exploration and laboratory testing of core samples that have been done for each of the sites to provide information for this analysis. Most of the previous similar, studies associated with nuclear waste isolation have relied on "generic" properties and/or geometries. Consequently, the results of this study should provide pertinent information for repository design because the data considered are site specific to the extent possible. 1.3 Methodology This study represents the first phase of a series of planned thermomechanical analyses of potential nuclear waste repositories in salt. This first phase involves the use of a baseline repository, which is summarized in Table I, to make a comparison of the thermal and thermomechanical responses for each of the four sites. The baseline repository concept simplifies the comparison of the four sites by fixing many parameters. The primary purpose of the planned second phase is to help optimize the repository design by performing a sensitivity or parametric study of the more important and controlling parameters. The parameters to be considered in this future sensitivity analysis will include room and pillar dimensions, areal thermal loading, and repository depth. These parameters are considered more influential than others since variations in their magnitudes should have a substantial effect on the thermal and thermomechanical responses. The room region encompasses the excavated repository facility. This includes one room- height of rock mass extending above the facility, below the bottom of the waste canisters, and horizontally beyond the repository edge. This analysis has been performed numerically with the finite element method using eight-noded isoparametric elements. The finite element programs are from the SPECTROM series of computer programs, which have been specifically developed to analyze rock mechanics problems. The thermal analyses employed SPECTROM-41 which has been documented by Svalstad (1981). The thermomechanical analyses were performed with SPECTROM-21(Fossum et al..., 1982). The scenario used in this study assumes the disposal rooms will be sealed, but not backfilled, during the initial 25 years after waste emplacement. Subsequently, the rooms are backfilled with crushed salt for an additional 25 years. After these 50 years of operation, the repository will be decommissioned and abandoned.
- North America > United States > Utah (1.00)
- North America > United States > Texas (1.00)
- Water & Waste Management > Solid Waste Management (1.00)
- Energy > Power Industry > Utilities > Nuclear (1.00)
An In Situ Determination Of The Thermal Conductivity Of Granitic Rock
Kuriyagawa, Michio (National Research Institute for Pollution and Resources) | Matsunaga, Isao (National Research Institute for Pollution and Resources) | Yamaguchi, Tsutomu (National Research Institute for Pollution and Resources)
SYNOPSIS: A field experiment was carried out to measure the temperature profile produced in a granitic rock by electrical heating, and the thermal conductivity as a function of temperature was obtained from these results. For this purpose, a cylindrical heater of 60 cm length was placed in the rock at a depth of 3 metres and kept at 440°C for 2,000 hours. Temperature was measured with thermocouples set at various distances from the heater to determine an in situ temperature profile. The temperature profile was then calculated using the Finite Element Method for various assumed values of the conductivity, and these results were compared with those measured. From these comparisons, the best fit of the thermal conductivity k(W/mK) to the data is expressed as a function of temperature T(K): k = 5.319 x10T-1.5507. RESUME: Une experience in situ à ete realisee pour determiner le profil thermique induit dans une roche granitique par chauffage electrique. On a derive de ces resultats la conductivite thermique en fonction de la temperature. Dans ce but un element chauffant cylindrique 60 cm de long a ete place dans la roche à 3 mètres de profondeur et maintenu pendant 2000 heures à 440°C. La temperature en a ete mesuree à l'aide des thermocouples à des distances allant de 0,5 à 11 mètres de l'element. Pour obtenir la conductivite de la roche le profil thermique mesure a ete compare avec le profil calcule parune methode d'elements finis pour plusieurs valeurs assumees de la conductivite. A partir de ces comparaisons la conductivite thermique k(W/mK) est representee comme fonction de la temperature T(K) par k = 5319(T-1,5507). ZUSAMMENFASSUNG: Ein in situ Versuch zur Ermittlung der Warmeleitfahigkeit eines Felses (granitischer Gneis) als Funktion der Temperatur wird beschrieben. Zu diesem Zweck wurde eine zylindrische Warmequelle im Gebirge eingebracht und 2 000 Stunden lang auf 440°C gehalten. Die Gebirgstemperaturen wurden mit nach der Finite Element Methode berechneten Modellen verglichen, wobei die Warmeleitfahigkeit und ihre Änderung mit der Temperatur variiert wurden. Die beste Anpassung an die gemessenen Temperaturen ergab sich, wenn fuer die Abhangigkeit der Warmeleitfahigkeit k(W/mK) von der Temperatur T(K) die Funktion k = 5,319 × 10T-1,5507 angenommen wurde. 1. INTRODUCTION In designing a Hot Dry Rock geothermal reservoir, an underground waste isolation plant, or developing mines and tunnels where the control of temperature is critical, it is important to know the thermal conductivity of the rock encountered. Methods of measuring conductivities using a small specimen have been developed and used widely. But there remains a question of how the thermal conductivity measured-in small specimens correlates with that of the in-situ rock mass. From this point of view, the field measurement of the thermal conductivity is necessary. Murphy, H.D. 1) obtained estimates of thermal conductivities from borehole measurements in a geothermal reservoir. This is a useful method for determining the in-situ thermal conductivity. This paper describes a field test using a line heater in the rock to determine the in-situ rock thermal conductivity and its dependence on temperature. A cylindrical electric heater was placed at the depth of 3 m inside the borehole and kept at high temperature for about three months. The thermal conductivity was also measured with specimens sampled from the test site and, a comparison was made between the values obtained from the field test and in the laboratory. 2. LAYOUT OF THE FIELD TEST The field experiment was carried out at Tochibora pit of Kamioka Mine, Mitsui Mining & Smelting Co. The location of the field is shown in Fig.1. Kamioka Mine is the one of the largest metals mines in Japan and produces primarily lead, zinc and silver. The test site selected is a roadway with the cross section of approximately 3 m × 3 m and the rock is formed of granitic gneiss. A cylindrical heater, 60 cm in length and 6 cm in diameter, was placed at the depth of 3 m inside a 10 cm diameter borehole drilled into the sidewall of the roadway. The gap between the heater and borehole was filled with fire-proof materials. Thermocouples for temperature measurement of the rock arranged at distances of 0.5, 1.0, 2.0 3.9 and 5.1 m from the heater. Fig.2 shows a schematic of the test layout. These were placed at a depth of 2.9 to 3.0 m. In the measurement boreholes, No.4 and 5 located 0.5 and 1.0 mfrom the heater, thermocouples with the length of 1m were placed to clarify the heat flow toward the free surface of the sidewall. Three other measurement boreholes, No.1, 2 and 3 in Fig.2 were drilled at 1m from the heater to obtain the anisotropy of the thermal conductivity of the rock. The anisotropy could not be determined because the relative position of the heater and thermocouples could not be measured exactly.
- Asia > Japan (0.35)
- North America > United States (0.29)
- Energy > Oil & Gas > Upstream (0.75)
- Energy > Renewable > Geothermal > Geothermal Resource (0.35)
SYNOPSIS: The heat transfer in the rock mass around mine openings is studied with reference to the Campiano Mine (Grosseto, Italy), where the geothermal gradient was measured to be approximately 0.08°C per meter depth. The following problems are considered:Laboratory tests carried out in order to determine the thermo-physical properties of the rock. In situ tests performed to measure the temperature distribution in the rock mass around mine openings and to evaluate the most important thermo-physical parameters of the rock mass. Analytical and numerical modelling performed in order to interpret the in situ tests and to predict the temperature distribution in the rock mass around mine openings. RESUME: On etudie la diffusion de la chaleur dans la roche autour des vides miniers dans le cas de haut gradient de temperature (0.08°C/m) dans la mine de Campiano (Grosseto, Italie). L'etude a ete realisee par: 1) essais en laboratoire pour deduire les proprietes thermo-physiques de la roche; 2) essais in situ pour mesurer la distribution de la temperature dans la roche autour des vides miniers et d'evaluer les plus importants paramètres thermiques au niveau de la roche in situ; 3) mise au point des modèles analytiques et numeriques ayant pour but d'interpreter les essais in situ et de predire la distribution de la temperature dans la roche. ZUSAMMENFASSUNG: Der Warmeaustausch im Gebirge um bergmannische Hohlraume wird in Bezu auf die Campiano Grube (Grosseto, Italien) untersucht, wo der geothermische Gradient einer Temperaturzunahme von 0.08°C je Meter Tiefe - nach eigenen Messungen - zu enbsprechen scheint. Man hat deswegen die folgenden Untersuchungen durchgefuehrt: 1) Laborversuche, um die Warmeeigenschaften des Felsens zu bestimmen. 2) In situ Messungen, um die Warmeverteilung in der Umgebung von bergmannischen Hohlraumen festzustellen und die wichtigsten Warmeparameter des Gebirges abzuschatzen. 3) Analytische und numerische Modelle wurden hergestellt, um die in situ Messungen wissenschaftlich zu erklaren und um die Ternperaturverteilung um Grubenhohlraume vorhersagen zu können. INTRODUCTION A number of very important engineering problems relate to heat transfer in rock masses. Among the most interesting examples, the following may be recalled: 1. the stabilization of rock by artificial freezing, for the purpose of excavation of wells and tunnels; 2. the industrial use of geothermal reservoirs; 3. the choice of underground spaces for radioactive waste storage; 4. the exploitation of minerals in deep mines, with high temperature conditions. With reference to the problem of evaluating the thermomechanical behavior of rock masses (i.e.) stress analysis and heat transfer of rock masses), the present state of knowledge is limited. For example, rock thermo-physical properties (e.g. thermal diffusivity and/or thermal conductivity; specific heat) are less known than mechanical properties (e.g. stress-strain laws, failure criteria, etc.). The need for obtaining additional data on rock thermo-physical properties in the laboratory and in situ is therefore well recognized. At the same time, appropriate analytical and numerical methods and solutions are to be developed for the study of heat transfer in rock masses around underground openings. This paper describes a number of problems relating to the analysis of heat transfer around underground openings in a deep mine near to Grosseto (Italy). The purpose is to obtain the basic data needed for predicting the temperature distribution in the rock mass and in the air where a mine opening is being excavated. The following problems are considered:Laboratory tests carried out in order to determine the rock thermo-physical properties. In situ tests performed to measure the temperature distribution in the rock mass around mine openings and to evaluate the rock mass thermo-physical parameters. Analytical and numerical modelling performed in order to interpret the in situ tests and to predict the temperature distribution in the rock mass around mine openings. THE MINE UNDER STUDY The mineral deposit is formed of pyrite, mixed (Pb, Zn, Cu) sulphurs, and pyrite and magnetite, with a total of 25 Mt presently estimated reserve. An evaporitic series, made mostly of anhydrite with dolomites, is above the deposit, with phyllitic rocks being below. A very high geothermal gradient (approximately 0.08 °c per meter-depth) is present. It is to be noted that Campiano is located approximately 20 km away from the well known Larderello geothermal reservoirs. In addition to the high temperature of the virgin rock mass (75°C at 500 m depth below sea level, near to 800 m below ground surface), a strong influence on the temperature conditions underground is that due to the heavy mechanized systems used for excavation purposes. For the purpose of the present study, the heat transfer problem in situ was examined, mainly by considering the rock mass thermal behavior around a drift (spiral decline) of a 20 m cross section, created in order to reach the orebody, Fig. 2. However, in a few cases, also the openings located in the ore and neighbouring rocks were considered.
- Geology > Mineral (1.00)
- Geology > Rock Type > Sedimentary Rock (0.49)
- Materials > Metals & Mining (1.00)
- Energy > Renewable > Geothermal (1.00)
- Energy > Oil & Gas > Upstream (0.88)
- Reservoir Description and Dynamics > Reservoir Characterization (1.00)
- Reservoir Description and Dynamics > Non-Traditional Resources > Geothermal resources (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Data Science & Engineering Analytics > Information Management and Systems (1.00)