Micromechanics of pressure-induced grain crushing in porous rocks

Journal Article · Wed Jan 10 00:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB01p00341· OSTI ID:5010225

Zhang, Jiaxiang; Wong, Teng-Fong; Davis, D M ^[1]

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1. State Univ. of New York, Stony Brook (United States)

The hydrostatic compaction behavior of a suite of porous sandstones was investigated at confining pressures up to 600 MPa and constant pore pressures ranging up to 50 MPa. These five sandstones (Boise, Kayenta, St.Peter, Berea, and Weber) were selected because of their wide range of porosity (5-35%) and grain size (60-460 {mu}m). The authors, tested the law of effective stress for the porosity change as a function of pressure. Except for Weber sandstone (which has the lowest porosity and smallest grain size), the hydrostat of each sandstone shows an inflection point corresponding to a critical effective pressure beyond which an accelerated, irrecoverable compaction occurs. The microstructural observations show that brittle grain crushing initiates at this critical pressure. The authors also observed distributed cleavage cracking in calcite and intensive kinking in mica. The critical pressures for grain crushing in sandstones range from 75 to 380 MPa. In general, a sandstone with higher porosity and larger grain size has a critical pressure which is lower than that of a sandstone with lower porosity and smaller grain size. The authors formulate a Hertzian fracture model to analyze the micromechanics of grain crushing. Assuming that the solid grains have preexisting microcracks with dimensions which scale with grain size, they derive an expression for the critical pressure which depends on the porosity, grain size, and fracture toughness of the solid matrix. The theoretical prediction is in reasonable agreement with experimental data as well as other data from soil and rock mechanics studies for which the critical pressures range over 3 orders of magnitude.

• OSTI ID: 5010225
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:B1; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
SANDSTONES
PRESSURIZATION
CALCITE
CLEAVAGE
COMPACTING
CORRELATIONS
CRACKS
CRITICAL PRESSURE
DEPTH
FRACTURE PROPERTIES
GRAIN SIZE
HIGH PRESSURE
HYDROSTATICS
MATHEMATICAL MODELS
MICA
MICROSTRUCTURE
MORPHOLOGICAL CHANGES
PORE PRESSURE
POROSITY
POROUS MATERIALS
ROCK MECHANICS
STRESS ANALYSIS
CARBONATE MINERALS
CRYSTAL STRUCTURE
DIMENSIONS
MATERIALS
MECHANICAL PROPERTIES
MECHANICS
MINERALS
PHYSICAL PROPERTIES
ROCKS
SEDIMENTARY ROCKS
SILICATE MINERALS
SIZE
THERMODYNAMIC PROPERTIES
580000* - Geosciences