Home About us Contact
|
Home About us Contact | ||
|
|
||
Deep Boreholes (deep + borehole)
Selected AbstractsIs advective heat transport significant at the Dead Sea basin?GEOFLUIDS (ELECTRONIC), Issue 3 2007E. SHALEV Abstract An understanding of heat flux is a necessary component in reconstructing tectonic, seismic, and hydrologic models of the Dead Sea basin. Heat may be transferred by both conduction and advection by groundwater. Although the conductive heat flux in Israel has been extensively measured to be approximately 40 mW m,2, there is still a debate about the total heat flux. Recently, the discharge of hot springs along the western Dead Sea shore has been determined to be 107 m3 year,1. Simple calculations show that the heat discharged by groundwater at these hot springs is of the same order of magnitude as the measured conductive heat flux in deep boreholes. Therefore the total heat flux could be significantly higher than 40 mW m,2. However, results of numerical modeling show that the current hot-spring heat discharge is two orders of magnitude greater than that predicted for steady-state conditions and can be explained by the rapid recession of the Dead Sea. [source] Real-time quadrupole mass spectrometer analysis of gas in borehole fluid samples acquired using the U-tube sampling methodologyGEOFLUIDS (ELECTRONIC), Issue 3 2006B. M. FREIFELD Abstract Sampling of fluids in deep boreholes is challenging because of the necessity of minimizing external contamination and maintaining sample integrity during recovery. The U-tube sampling methodology was developed to collect large volume, multiphase samples at in situ pressures. As a permanent or semi-permanent installation, the U-tube can be used for rapidly acquiring multiple samples or it may be installed for long-term monitoring applications. The U-tube was first deployed in Liberty County, TX to monitor crosswell CO2 injection as part of the Frio CO2 sequestration experiment. Analysis of gases (dissolved or separate phase) was performed in the field using a quadrupole mass spectrometer, which served as the basis for determining the arrival of the CO2 plume. The presence of oxygen and argon in elevated concentrations, along with reduced methane concentration, indicates sample alteration caused by the introduction of surface fluids during borehole completion. Despite producing the well to eliminate non-native fluids, measurements demonstrate that contamination persists until the immiscible CO2 injection swept formation fluid into the observation wellbore. [source] Origin of deep saline groundwaters in the Vienne granitic rocks (France): constraints inferred from boron and strontium isotopesGEOFLUIDS (ELECTRONIC), Issue 2 2001J. Casanova Abstract As part of a preliminary geological characterization programme to assess the feasibility of an underground laboratory in granitic rock, a series of 17 deep boreholes (maximum depth, 900 m) was drilled by ANDRA in the Vienne district, France. A salinity gradient was demonstrated in the granitic waters with concentrations varying from approximately 1 g L,1 at 150 m depth at the top of the basement (beneath the sedimentary cover) to 10 g L,1 in the deeper part (from 400 to 600 m depth). Sr and B isotope ratios were measured in order to better understand the origin of the salinity and to evaluate the degree of water,rock interaction in the system. The results obtained were compared to those of mineral spring waters emerging from the granitic basement in the Massif Central. Evidence in support of a significant marine contribution include: (i) the Cl,Br investigations agree with a marine origin for the saline groundwaters without evolution from seawater; (ii) the 87Sr/86Sr ratio of the Vienne deep groundwaters (0.7078,0.7084) is in agreement with a palaeo-seawater isotopic signature; (iii) measured ,11B values for the deepest brine samples are enriched in 11B (up to 36.1,) relative to the granitic springs. The combined use of ,11B, Cl, B, Br, Sr contents and 87Sr/86Sr ratios makes it possible to define and quantify a mixing model between marine and crustal end-members in order to explain the origin of the deep saline groundwaters in the Vienne granitic rocks. [source] Present-day stress in the surroundings of 2009 L'Aquila seismic sequence (Italy)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2010Maria Teresa Mariucci SUMMARY The axial zone of the Apenninic belt in central Italy is a tectonically active region affected by post-orogenic Quaternary extension. The present-day stress field is characterized by a minimum horizontal stress (Shmin) , NE,SW oriented, derived mainly from earthquake focal mechanisms and secondarily from borehole breakouts and fault data. The paper describes the computation of the Shmin orientation along two deep boreholes located in the vicinity of the area hit by the 2009 April 6, Mw 6.3 L'Aquila earthquake. The analysed wells show breakout zones at a depth range between 1.4 and 4.6 km, giving precious information on a depth interval usually not investigated by any other data. The results show an Shmin N81 ± 22° and N74 ± 10° oriented for Varoni 1 and Campotosto 1 wells, respectively. The comparison among the breakouts, the 2009 seismic sequence, the past seismicity and the Quaternary faults indicates a small rotation of Shmin orientation from , NE, in the southern, to , ENE in the northern sector of the study area, where the wells are located. These differences are linked both to the natural variations of data and to the orientation of the main tectonic structures varying from NW,SE in the Abruzzi region to , N,S moving toward the Umbro-Marchean Apennines. The identification of constant Shmin orientations with depth derived from all the examined active stress data, confirms the breakouts as reliable stress indicators also for aseismic areas. [source] A field test of imaging properties of rotational invariants of the magnetotelluric impedance tensorGEOPHYSICAL PROSPECTING, Issue 3 2005László Szarka ABSTRACT A part of the Békés Basin (an extensional sub-basin of the Pannonian Basin, where the basement under thick Pannonian sediments is well known from deep boreholes and from seismic measurements, and where many magnetotelluric (MT) soundings have been carried out for frequencies ranging from 1 to 10,3 Hz) was selected as a test area to assess the imaging performances of various apparent-resistivity definitions computed with rotational invariants of either the real part of the complex impedance tensor, or its imaginary part, or both. A comparison (based on earlier 3D numerical studies) has been made between the magnetotelluric images obtained in this way and the depths to the high-resistivity basement, as known from boreholes and seismic investigations. The correlation coefficient between the series of basement depth values at 39 MT sites and the apparent-resistivity values was found to be stronger and high correlation appeared at a shorter period when it was computed with apparent resistivities based on the real tensor rather than with apparent resistivities based on the imaginary tensor. In the light of our studies, ,ReZ and the impedance phase seem to be more informative than any other combination of magnetotelluric interpretation parameters. [source] GEOCHEMICAL AND GEOPHYSICAL ANOMALIES AT THE ZDANICE OIL- AND GASFIELD, SE CZECH REPUBLICJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2008M. Matolin Oil at the Zdanice field in the SE Czech Republic is reservoired at a depth of 900 m in weathered Precambrian granitoids and Lower Miocene sandstones and conglomerates. Tertiary claystones, siltstones and sandstones form the top seal. Surface gamma-ray spectrometry carried out along two profiles across the field (6,880 m and 8,335 m in length, respectively) found perceptible decreases of K, U, and Th concentrations relative to background values. This can be explained in terms of enhanced leaching of these radionuclides by groundwater acids derived from hydrocarbons. Observed increases in radon and thoron in soil gas above the oil-producing zone at Zdanice may be caused by enhanced gas emanation from U- and Th-bearing minerals decomposed by groundwater acids. Laboratory analyses of 444 samples collected from 18 shallow boreholes (20 m deep) pointed to a trend of decreasing K, U and Th concentrations above the oil-producing zone at Zdanice. Decreases in rock porosity and organic carbon content were also noted together with an increase in mineralogical density, magnetic susceptibility and sulphur content. Petrophysical analyses of 330 samples from deep boreholes showed lower values of K and U in samples from oil-producing wells. These observations of minor petrophysical alterations in rocks overlying the Zdanice oilfield may be characteristic and may be applicable to hydrocarbon exploration operations elsewhere. [source] Prediction of formation temperatures in permafrost regions from temperature logs in deep wells,field casesPERMAFROST AND PERIGLACIAL PROCESSES, Issue 3 2003I. M. Kutasov Abstract Important data on the thermal regime of the Earth's interior come from temperature measurements in deep boreholes. Drilling greatly alters the temperature field of earth materials surrounding the wellbore. In permafrost regions, due to thawing of adjacent strata during drilling, representative data can be obtained only by repeated observations over a long period of time. In this paper we predict undisturbed formation temperatures (and geothermal gradients) from shut-in temperature logs in deep wells. The main features of the method are: (1) in the permafrost section of the well, the starting point in the well thermal recovery is moved from the end of well completion to the moment of time when the refreezing of enclosing strata was completed; it takes into account the refreezing of thawed material in a temperature interval; and (2) below the permafrost base, the starting point in the well thermal recovery is moved from the end of well completion to the moment of time when the first shut-in temperature log was taken. A generalized formula to process field data (for the well sections below and above the permafrost base) is presented. Temperature logs conducted in five wells verify the method. Copyright © 2003 John Wiley & Sons, Ltd. [source] Three deep Alpine-permafrost boreholes in Svalbard and ScandinaviaPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2001Ketil Isaksen Abstract The presence and thermal character of permafrost reflect past and present surface energy balances plus the heat flux from the Earth's interior. Analysis of permafrost ground temperatures constitutes a key research tool for detecting thermal anomalies caused by twentieth-century warming. Three deep boreholes in alpine permafrost were drilled in Svalbard and Scandinavia and form part of the latitudinal transect of mountain permafrost boreholes through the mountains of Europe established under the EU PACE (Permafrost and Climate in Europe) project. The northernmost borehole in the transect, at Janssonhaugen (depth 102 m), western Svalbard (78°10,46,,N, 16°28,01,,E, 270 m ASL) was drilled in May 1998. In Scandinavia, boreholes were drilled at Tarfalaryggen (depth 100 m), northern Sweden (67°55,09,,N, 18°38,29,,E, 1550 m ASL) in March 2000 and at Juvvasshøe (depth 129 m), southern Norway (61°40,32,,N, 08°22,04,,E, 1894 m ASL) in August 1999. Permafrost thickness at Janssonhaugen is estimated as approximately 220 m. The temperature profiles on Tarfalaryggen and Juvvasshøe show anomalously low geothermal gradients, indicating low heat flow through thick permafrost (,350 m and ,380 m respectively). Palaeoclimatic analysis based on inversion modelling of the ground temperature measurements at Janssonhaugen shows near surface warming of 1.5 ± 0.5 °C during the twentieth century. Both the Tarfalaryggen and Juvvasshøe boreholes also reveal thermal anomalies, which reflect a surface warming over the past decades, with a magnitude of approximately 0.5,1.0 °C. Copyright © 2001 John Wiley & Sons, Ltd. RÉSUMÉ L'existence d'un pergélisol ainsi que ses caractères thermiques reflètent la balance entre l'énergie de surface (passée et actuelle) et le flux de chaleur interne de la terre. L'étude des températures du pergélisol constitue ainsi une recherche fondamentale pour détecter les anomalies thermiques dues au réchauffement du vingtième siècle. Trois sondages profonds dans le pergélisol alpin ont été réalisés au Svalbard et en Scandinavie. Ils constituent une partie du transect en latitude de sondages du pergélisol de montagne réalisé dans le cadre du projet de l'Union Européenne Pace (Pergélisol et Climat en Europe). Le sondage le plus septentrional du transect a été foré en mai 1998 à Janssonhaugen (profondeur 102 m), à l'ouest de Svalbard (78°10,46,,N, 16°28,01,,E, à 270 m d'altitude). En Scandinavie, des sondages ont été réalisés en mars 2000 à Tarfallaryggen (profondeur 100 m) au nord de la Suède (67°55,09,,N, 18°38,29,,E, à 1550 m d'altitude) et en août 1999 à Juvvasshoe (profondeur 129 m), au sud de la Norvège (61°40,32,,N, 08°22,04,,E, à 1894 m d'altitude). L'épaisseur du pergélisol à Janssonhaugen est approximativement de 220 m. Les profils de température à Tarfalaryggen et à Juvvasshoe montrent des gradients géothermiques anormalement faibles, indiquant un faible écoulement de chaleur au travers d'un pergélisol épais (respectivement d'environ 350 m et 380 m). Des analyses paléoclimatiques basées sur un modèle d'inversion des mesures de la température du sol à Janssonhaugen indiquent un réchauffement près de la surface de 1.5 0.5 °C pendant le 20e siècle. A la fois à Tarfalarygen et à Juvvasshoe, les anomalies thermiques existantes révèlent un réchauffement de la surface d'une ampleur de approximative de 0.5 à 1.0 °C au cours des dernières décades [source] | ||||||||||