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[en] Casing deformation in wells is a common problem in many geothermal fields. Casing remediation is necessary to keep wells in production and occasionally, to even enter the well for an approved plug and abandonment procedure. The costly alternative to casing remediation is to incur the expense of drilling a new well to maintain production or drilling a well to intersect a badly damaged well below the deformation for abandonment purposes. The U.S. Department of Energy and the Geothermal Drilling Organization sponsor research and development work at Sandia National Laboratories in an effort to reduce these remediation expenditures. Sandia, in cooperation with Halliburton Energy Services, has developed a low cost, commercially available, bridge-plug-type packer for use in geothermal well environments. This report documents the development and testing of this tool for use in casing remediation work
[en] Most hydrogeological information is obtained from boreholes under the assumption that the medium is homogeneous. Ironically, permeable media are known to be extremely heterogeneous. The question, then, is to what extent does this heterogeneity affect the interpretation process and the meaning of the resulting parameters. The objective of this report is to summarize the work performed at UPC for ENRESA during the last six years on the topic of flow to a well. In essence, the work can be classified in steady-state and transient analyses. Regarding steady-state flow to a well, we derive the value of effective transmissivity (the one relating mean flux and mean head gradient) find out that it grows form the harmonic mean (for small radial distance) towards the geometric mean (for large radius). We derive an expression for equivalent transmissivity (that is the one that yields the right pumping rate given a heterogeneous T field). We compare our equation to other empirical approaches and find out that it works quite well. Finally, we derive a generalized Thiem equation that yields head around a pumping well under steady state conditions. Regarding transient flow to a well, we analyze in detail the meaning of parameters estimated using Jacob- Cooper method. We derive an expression for the transmissivity estimated using this method. Such transmissivity is independent of the location of the observation well, which is consistent with the frequent field observation that draw downs at different wells plot as straight lines with the same slope at late times. More importantly, we find that this estimate equals the effective transmissivity. On the other hand, the value of estimated storage coefficient appears to reflect the degree of connection between pumping and observation wells rather than actual storativity. Finally, we find the specific capacity (pump rate divided by drawdown) may correlate better with local T than the value derived from a pump test, which tends to be biased towards the effective T even for relatively short tests. (Author)
[en] This report describes the work that was done to prepare the Phase II proposal for an enhanced geothermal system based on the use of horizontal well to increase production of reservoir fluids from geothermal wells
[en] δDH2O values (-61 to -53 per mil) of fluid inclusions in quartz that were ejected from initial discharge of geothermal wells, have values that are 10-30 per mil lower than the water from which the quartz was precipitated. Hydrogen isotope values of water extracted from epithermal vein quartz from the Waihi and Hishikari gold-silver deposits are 20-60 per mil lower than present day meteoric water, but are consistent with mixing trends indicated by other data. Fine-grained quartz from the Hishikari epithermal veins contain anomalous high amounts of water (up to 1.5 wt.%) which is interpreted to be trapped in submicrometer size ('invisible') inclusions during the crystallisation of amorphous and/or polycrystalline silica to form quartz. δD values of water extracted by thermal decrepitation from fluid inclusions in quartz should be interpreted with caution as they do not necessarily represent the original composition of the geothermal water. (author). 18 refs., 5 figs
[en] Radon concentration was monitored during the flow tests of well IC-09 at the Chingshui geothermal field. The radon concentration was found to increase from 54 ± 29 to 983 ± 65 Bq/m3 as a step function of production time, or cumulative production. The observed radon behavior can be explained by a radial composite model with the carbonate scales deposited in the skin zone near the well. The radius of skin zone near well IC-09 can be estimated with radon data at about 20 m using a plug flow model. Monitoring natural radon during the well flow tests is a helpful tracer to diagnose the formation damage near the well.
[en] Full text: Chemical analysis of 38 wells discharge thermal fluids in central Jordan near (Khan Ezabeeb area), and chemical characteristics of the thermal fluids were studied. 6 samples from cold water and 6 samples of thermal water were sampled from all over the Jordan for comparison purposes, 22 and 7 samples were reviewed and studied for stable and radioactive isotope respectively. The data was interpreted by the use of WATCH program for speciation and construction of mineral equilibrium diagrams and other graphical presentation and classification. The maximum reservoir temperature for the wells predicted by calculation of various geothermometers exceeds 80 deg. C. There is an evidence of mixing with cold water, for plot of O18 versus Cl and a linear relationship between Cl versus Br and B. The calculated Quartz and Chalcedony, for the geothermometers values of the geothermal well waters indicate that reservoir temperature about 60 deg. C - 80 deg. C, and the Na-K-Ca geothermometers give mostly higher values for the wells, however, the calculation of mineral saturation indicates that the geothermal water shows fluid from some of the wells which is about to be close to the equilibrium at 115 deg. C, and some degree of under saturation with anhydrite, fluorite and chalcedony. The chemical composition of the waters in the studied area is governed by water rock interaction in area concerned and the (Cl-SO4-HCO3), (Na - K - Mg) triangular diagrams and stable isotopes were used to classify the geothermal and cold waters and to study some processes in the geothermal system, the geothermal waters are bicarbonate type with some samples of chloride and sulfite type, indicating reactions with sedimentary rocks (sandstone), the origin of the fluids are of meteoric water and the age extends 20,000 up to 38,000 years. (author)
[en] The structural evolution of faults in foreland basins is linked to a complex basin history ranging from extension to contraction and inversion tectonics. Faults in the Upper Jurassic of the German Molasse Basin, a Cenozoic Alpine foreland basin, play a significant role for geothermal exploration and are therefore imaged, interpreted and studied by 3D seismic reflection data. Beyond this applied aspect, the analysis of these seismic data help to better understand the temporal evolution of faults and respective stress fields. In 2009, a 27 km2 3D seismic reflection survey was conducted around the Unterhaching Gt 2 well, south of Munich. The main focus of this study is an in-depth analysis of a prominent v-shaped fault block structure located at the center of the 3D seismic survey. Two methods were used to study the periodic fault activity and its relative age of the detected faults: (1) horizon flattening and (2) analysis of incremental fault throws. Slip and dilation tendency analyses were conducted afterwards to determine the stresses resolved on the faults in the current stress field. Two possible kinematic models explain the structural evolution: One model assumes a left-lateral strike slip fault in a transpressional regime resulting in a positive flower structure. The other model incorporates crossing conjugate normal faults within a transtensional regime. The interpreted successive fault formation prefers the latter model. The episodic fault activity may enhance fault zone permeability hence reservoir productivity implying that the analysis of periodically active faults represents an important part in successfully targeting geothermal wells.
[en] The potential of geothermal energy utilization in Jordan was discussed. The report gave a summary of the location of geothermal anomalies in Jordan, and of ongoing projects that utilize geothermal energy for greenhouse heating, fish farming, refrigeration by absorption, and water desalination of deep aquifers. The problems facing the utilization of geothermal energy in Jordan were identified to be financial (i.e. insufficient allocation of local funding, and difficulty in getting foreign financing), and inadequate expertise in the field of geothermal energy applications. The report gave a historical account of geothermal energy utilization activities in Jordan, including cooperation activities with international organizations and foreign countries. A total of 19 reports already prepared in the areas of geochemical and hydrological studies were identified. The report concluded that the utilization of geothermal energy offers some interesting economic possibilities. (A.M.H.). 4 refs. 1 map
[en] Fine-grained quartz and adularia in the Hishikari (Japan) crustiform epithermal veins, contain up to ∼ 1 wt.%, excluding adsorbed and fluid inclusion water. Water extracted from the veins is predominantly from sub-micron size fluid inclusions in quartz which are the remnants of water from precursor hydrous silica polymorphs. Quartz-rich parts of veins have total water contents >0.5 wt.%, and constant δD values (-75 per thousand). These δD values are lower than present day meteoric water (-50 per thousand). Hydrogen isotope analyses of amorphous silica and water from geothermal power plants and natural springs suggest that a 20 to 0 per thousand fractionation occurs between the precursor silica polymorphs and water at epithermal temperatures (150 degrees C to 200 degrees C). Extraction of water from fine-grained epithermal quartz is not considered to be a suitable technique for determining the δDH2O values of palaeo-geothermal waters. (author). 16 refs., 7 figs
[en] Build up of scale deposits on the walls of geothermal wells can occur rapidly due to the high dissolved solids content of geothermal fluids. Scale formation is a significant problem for both the well and for surface heat transfer equipment. Geothermal brines contain a wide variety if dissolved salts including carbonates, silicates, sulfates, and metal sulfides. One technology recently proposed for scale removal is the use of an ultrasonic device. In the present effort we apply cavitation in a more direct manner by the use of acoustically enhanced cavitating water jets which can be made to be much more efficient and aggressive than ultrasonic devices. Cavitating and self-resonating jet technologies have been proven to enhance the erosive power of liquid jets in a number of cutting, cleaning, and drilling applications. In this study we investigated two related technologies - one that employs cavitation and one that breaks the jet up into a series of slugs that produce water hammer type pressures upon impact. These technologies enable operation in both submerged and nonsubmerged conditions