Hydraulic-fracture growth in dipping anisotropic strata as viewed through the surface deformation field
In 1983 and 1984 Oak Rdige National Laboratory conducted a series of precision ground deformation measurements before, during, and after the generation of several large hydraulic fractures in a dipping member of the Cambrian Conasauga Shale. Each fracture was produced by the injection of approximately 500,000 L of slurry on a single day. Injection depth was 300 m. Leveling surveys were run several days before and several days after the injections. An array of eight high-precision borehole tiltmeters monitored ground deformations continuously for a period of several weeks. Analysis of the leveling and the tilt measurements revealed surface uplifts as great as 25 mm and tilts of tens of microradians during each injection. Furthermore, partial recovery (subsidence) of the ground took place during the days following an injection, accompanied by shifts in the position of maximum resultant uplift. Interpretation of the tilt measurements is consistent with stable widening and extension of hydraulic fractures with subhorizontal orientations. Comparison of the measured tilt patterns with fracture orientations established from logging of observation wells suggests that shearing parallel to the fracture planes accompanied fracture dilation. This interpretation is supported by measured tilts and ground uplifts that were as much as 100 percent greater than those expected from fracture dilation alone. Models of elastically anisotropic overburden rock do not explain the measured tilt patterns in the absence of shear stresses in the fracture planes. This work represents the first large-scale hydraulic-fracturing experiment in which the possible effects of material anisotropy and fracture-parallel shears have been measured and interpreted.
- Research Organization:
- Applied Geomechanics, Inc., Santa Cruz, CA (USA); Oak Ridge National Lab., TN (USA); Texas A and M Univ., College Station (USA). Center for Tectonophysics
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5501808
- Report Number(s):
- CONF-850671-19; ON: DE85014141
- Country of Publication:
- United States
- Language:
- English
Similar Records
Uplifts and tilts at earth's surface induced by pressure transients from hydraulic fractures
Related Subjects
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
COMMINUTION
DEFORMATION
FAILURES
FRACTURES
FRACTURING
GROUND UPLIFT
HYDRAULIC FRACTURES
HYDRAULIC FRACTURING
LOW-LEVEL RADIOACTIVE WASTES
MATERIALS
ORIENTATION
RADIOACTIVE MATERIALS
RADIOACTIVE WASTES
ROCKS
SEDIMENTARY ROCKS
SHALES
WASTES