Alignment of near-surface inclusions and appropriate crack geometries for geothermal hot-dry-rock experiments

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Geophysical Prospecting; (USA)

DOI:https://doi.org/10.1111/j.1365-2478.1990.tb01866.x· OSTI ID:6822155

Crampin, S ^[1]

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1. Edinburgh Anisotropy Project, British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, Scotland (GB)

Ubiquitous splitting of seismic shear-waves indicated that most rocks in the upper half of the crust are pervaded by stress-aligned fluid-filled inclusions, called EDA-cracks. These inclusions are expected to be aligned perpendicular to the minimum compressional stress by stress relationships similar to those aligning industrial hydraulic fractures. At depths where the overburden stress is sufficiently large (typically below a few hundred metres) this minimum stress is usually horizontal, so that the EDA-cracks and hydraulic fractures are typically aligned vertically, striking parallel or subparallel, to the direction of maximum compression. This is confirmed by the polarizations of the split shear-waves along raypaths at depth in the crust. At the free surface, however, the vertical stress is zero (or approximately zero) and cracks (and hydraulic fractures) at shallow depths in intact rock tend to be horizontal.

• OSTI ID: 6822155
• Journal Information: Geophysical Prospecting; (USA), Vol. 38:6; ISSN 0016-8025
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
GEOTHERMAL FIELDS
HYDRAULIC FRACTURING
HOT-DRY-ROCK SYSTEMS
CRACK PROPAGATION
GEOMETRY
GEOTHERMAL EXPLORATION
SEISMIC SURVEYS
SHEAR
STRESS ANALYSIS
COMMINUTION
ENERGY SYSTEMS
EXPLORATION
FRACTURING
GEOPHYSICAL SURVEYS
GEOTHERMAL SYSTEMS
MATHEMATICS
SURVEYS
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions
150301 - Geothermal Exploration & Exploration Technology- Geophysical Techniques & Surveys
150906 - Geothermal Engineering- Reservoir Stimulation & Extraction Technology