[PDF] Geothermal Injection Monitoring Project eBook

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Page : pages
File Size : 22,2 MB
Release : 1981
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Background information is provided on the geothermal brine injection problem and each of the project tasks is outlined in detail. These tasks are: evaluation of methods of monitoring the movement of injected fluid, preparation for an eventual field experiment, and a review of groundwater regulations and injection programs. (MHR).

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Page : pages
File Size : 22,79 MB
Release : 1982
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The feasibility of using remote geophysical techniques to monitor the movement of injected brine has been evaluated. It was established that no single approach is likely to be identified that can be used to accurately monitor the precise location of the injected fluid. Several approaches have been considered in parallel because they add new dimensions to the existing monitoring capabilities, and are likely to cover a range of applications at a variety of geothermal sites. These include: microseismicity - a seismic net is used to record small magnitude events associated with injection; streaming potential - self potential anomalies produced by a moving fluid identify fluid flow direction; cross borehole geotomography - two-dimensional image of flow pathways is constructed using electromagnetic waves; and well pressure response to solid earth tide - changes in pore pressures are used to discriminate fracture/pore porosity and estimate fracture orientations.

Author : Lawrence Berkeley Laboratory
Publisher :
Page : pages
File Size : 30,18 MB
Release : 1983
Category : Geothermal reservoirs
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Injection into an idealized geothermal reservoir is considered, assuming that the injected water differs in temperature and salinity from in-place fluids. Changes in formation resistivity resulting from temperature and salinity variations are evaluated, and numerical simulation methods are used to predict effects which would be observed by means of dc resistivity monitoring. The resistivity calculations were performed using a three-dimensional computer code to simulate results from two different resistivity arrays, a dipole-dipole array and a downhole-surface array. Calculations show that the dipole-dipole method is relatively insensitive to changes due to injection , but downhole-surface measurements are very sensitive. From the simulated downhole-surface measurements a bell-shaped curve for resistivity change is obtained, from which the position of the chemical front may be approximately determined. Resistivity changes from temperature variations are rather small and probably cannot be detected in field measurements. Resistivity measurements are more than twice as sensitive when injected water is more saline than the in-situ reservoir fluid. This suggests that it may be easier to monitor the location of injected water if geothermal brine is reinjected rather than fresher water.