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An experimental study of the physical and chemical property changes occurring during the smectite to illite reaction

Conference · · AAPG Bulletin
OSTI ID:6592783
; ; ;  [1]
  1. Scripps Institution of Oceanography, La Jolla, CA (United States)
Smectite dehydration and the formation of illite releases significant amounts of fluid deep within sedimentary basins. The release of water from smectite and the resulting physical property changes have been linked to the generation of significant overpressures and may also assist in the primary migration of hydrocarbons. Little quantitative data exists, however, as to how chemical and physical property changes may be coupled under in situ stress conditions. Presented here are the initial results from a one dimensional consolidometer system in which a K-smectite was reacted under differential stress conditions at temperatures up to 250[degrees]C. Sample volume, permeability and effluent fluid compositions are monitored through out the experiments. Partial collapse of the K-smectites occurred in all runs, with rapid dehydration apparently taking place at T close to 100[degrees]C. Initial samples were bilayer hydrates in the 0.5M KCI pore fluids used in the experiments. Dilution of the output fluid suggests the loss of two layers of water. Samples heated to <115[degrees]C and were still subsequently expandable, while the samples run at 250[degrees]C showed some irreversible collapse (illitization) after glycolation. Accelerated volumetric creep and permeability reductions occurred during heating increments, with over an order of magnitude reduction in permeability occurring during some runs.
OSTI ID:
6592783
Report Number(s):
CONF-960527--
Conference Information:
Journal Name: AAPG Bulletin Journal Volume: 5
Country of Publication:
United States
Language:
English