Subsurface fracture mapping from geothermal wellbores. Final report
To advance the state-of-the-art in Hot Dry Rock technology, and evaluation is made of (1) the use of both electromagnetic and acoustic radar to map far-field fractures, (2) the use of more than twenty different conventional well logging tools to map borehole-fracture intercepts, (3) the use of magnetic dipole ranging to determine the relative positions of the injection well and the production well within the fractured zone, (4) the use of passive microseismic methods to determine the orientation and extent of hydraulic fractures, and (5) the application of signal processing techniques to fracture mapping including tomography, holography, synthetic aperture, image reconstruction, and the relative importance of phase and amplitude information. It is found that according to calculations, VHF backscatter radar has the potential for mapping fractures within a distance of 50 +- 20 meters from the wellbore. A new technique for improving fracture identification is presented. The range of acoustic radar is five to seven times greater than that of VHF radar when compared on the basis of equal resolution, i.e., equal wavelengths. Analyses of extant data indicate that when used synergistically the (1) caliper, (2) resistivity dipmeter, (3) televiewer, (4) television, (5) impression packer, and (6) acoustic transmission are useful for mapping borehole-fracture intercepts. A new model of hydraulic fracturing is presented which indicates that a hydraulic fracture is dynamically unstable; consequently, improvements in locating the crack tip may be possible. The importance of phase in signal processing is stressed and those techniques which employ phase data are emphasized for field use.
- Research Organization:
- H-Tech Labs., Inc., Santa Monica, CA (USA)
- DOE Contract Number:
- AC04-81AL16863
- OSTI ID:
- 6628585
- Report Number(s):
- DOE/AL/16863-T1; ON: DE84008842
- Resource Relation:
- Other Information: Portions are illegible in microfiche products. Original copy available until stock is exhausted
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC FRACTURES
MAPPING
HOT-DRY-ROCK SYSTEMS
BOREHOLES
FRACTURED RESERVOIRS
GEOTHERMAL WELLS
HYDRAULIC FRACTURING
INJECTION WELLS
WELL LOGGING
CAVITIES
COMMINUTION
ENERGY SYSTEMS
FRACTURING
GEOLOGIC STRUCTURES
GEOTHERMAL SYSTEMS
WELLS
Geothermal Legacy
150301* - Geothermal Exploration & Exploration Technology- Geophysical Techniques & Surveys