Direct observation of hydraulic fractures: behavior at a formation interface
Hydraulic fracture experiments have been conducted to examine fracture behavior at a formation interface. These experiments are being conducted near an existing tunnel complex and mineback through the region allows for the direct observation and characterization of the fracture system. Two hydraulic fractures were created above and below an ash fall tuff--welded tuff formation interface. These formations, respectively, have significant differences in their elastic moduli (0.5 x 10/sup 6/, 5.0 x 10/sup 6/ psi), Poisson's ratios (0.30, 0.21) and porosities (45, 13%). Conventional fracture calculations were used to design rectangular, vertical fractures of 50 ft height and 600 ft total length; 256 and 117 bbl were injected at 6 bbl/min into the ash fall and welded tuff zones, respectively. Mineback along the interface has revealed a total fracture length of 150 ft at this level. The fracture which initiated in the low modulus ash fall tuff broke upwards into the higher modulus welded tuff. Analysis of the fracture behavior is under way. 19 figures, 2 tables.
- Research Organization:
- Sandia Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- EY-76-C-04-0789
- OSTI ID:
- 6793295
- Report Number(s):
- SAND-78-1935
- Country of Publication:
- United States
- Language:
- English
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