A two-dimensional finite difference model of pore pressure evolution within and below a moving thrust sheet
Conference
·
· Geological Society of America, Abstracts with Programs; (United States)
OSTI ID:5639485
- Texas A and M Univ., College Station, TX (United States). Dept. of Geology
The authors have investigated the mechanisms responsible for the evolution of excess pore pressures within and beneath a ramping thrust sheet and the sensitivity of pore pressure to a variety of physical parameters. Coupled pore pressure and temperature equations were solved numerically in two dimensions using a generalized hydrostratigraphy of North American thrust belts; both deposition and thrust loading were modeled. The dominant mechanisms controlling pore pressure evolution were fluid flow and compression of pore space by vertical loading; thermal expansion of the fluids was found to be insignificant in generating excess pore pressures. The results of the modeling predict that it is possible to generate high pore pressure to lithostatic pressure ratios R within thrust belts by depositional loading prior to thrusting. High values of R are generated and maintained during thrust loading for reasonable assumptions about the conditions thought to have existed in thrust belts. Values of R were not constant throughout the model. The highest R values tended to concentrate near the surface of the model and within and below the toe of the thrust sheet. The magnitude and distribution of excess pore pressures and R values were found to be especially sensitive to variations in permeability. Excess pore pressure generation by compression exceeded pore pressure dissipation by fluid flow for permeabilities greater than approximately 10[sup [minus]16] m[sup 2] produced hydrostatic pore pressure gradients. The models demonstrate that permeability anisotropy and inhomogeneity due to lithologic variations may exert a strong control on the magnitude and spatial distribution of excess pore pressures within thrust belts.
- OSTI ID:
- 5639485
- Report Number(s):
- CONF-921058--
- Conference Information:
- Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
- Country of Publication:
- United States
- Language:
- English
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