Anomalous fracture-extension pressure in granitic rocks

Conference · Sun Jan 01 04:00:00 EST 1978

OSTI ID:5057304

Aamodt, R L; Potter, R M

Fracture-extension pressures appreciably higher than the least principal earth-stress were observed in hydraulic fractures formed in a pair of 3 km (9600 ft) deep boreholes drilled near the Valles Caldera in northern New Mexico. Pressurization of open wellbores in rock containing preexisting fractures may open these fractures, instead of creating new fractures at right angles to the least principal stress. The pressure necessary to flow into these fractures may be appreciably higher than the least principal stress. Upon sand-propping one such pre-existing fracture, a lower fracture extension pressure was observed. A second fracture in a parallel well-bore 92 m (300 ft) away, at the same depth of 2 km (6500 ft) exhibited the lower fracture extension pressure without propping, but with about 90/sup 0/ difference in fracture direction. Fractures created through perforations at a depth of 3 km (9600 ft) not only exhibited breakdown pressures upon initial pressurization, but sometimes even higher ''breakdown'' pressures upon repressurization. These phenomena may be of interest in the interpretation of earth stress measurements made by hydraulic fracturing.

• Research Organization: Los Alamos Scientific Lab., N.Mex. (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5057304
• Report Number(s): LA-UR-78-548; CONF-780509-3
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150901 -- Geothermal Engineering-- Drilling Technology & Well Hardware
150906* -- Geothermal Engineering-- Reservoir Stimulation & Extraction Technology
BOREHOLES
CAVITIES
COMMINUTION
DIAGRAMS
FRACTURING
GEOTHERMAL SYSTEMS
GRANITES
Geothermal Legacy
HOT-DRY-ROCK SYSTEMS
HYDRAULIC FRACTURING
IGNEOUS ROCKS
NEW MEXICO
NORTH AMERICA
PRESSURE DEPENDENCE
ROCKS
STRESSES
USA