Chemical equilibria and fluid flow during compaction diagenesis of organic-rich geopressured sediments.

Persistent Link:
http://hdl.handle.net/10150/184351
Title:
Chemical equilibria and fluid flow during compaction diagenesis of organic-rich geopressured sediments.
Author:
Capuano, Regina Marie.
Issue Date:
1988
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The effects of geopressuring and kerogen decomposition on mineral-fluid equilibria were calculated in order to predict the diagenetic-alteration mineralogy produced in equilibrium with kerogen-rich, geopressured sediments. These calculations indicate that several processes specific to kerogen-rich geopressured sediments contribute to the development of a characteristic alteration mineralogy. These processes are: (1) the upward flow of fluids in geopressured sediments, in contrast to the generally downward flow of fluids in normally-pressured sediments; (2) the coincidence of the depths of geopressuring (2-3 km; Fertl et al., 1976), with the geothermal temperatures necessary for CO₂ release (100°-135°C; Hunt, 1979), and CH₄ release (>90°C; Hunt, 1979); and (3) the opposing rates of sediment burial and CO₂ and CH₄ transfer into the upward-flowing fluids, which result in the geopressured pore fluids becoming enriched, and in some cases saturated, with respect to CO₂ and CH₄. Three patterns of mineral deposition during diagenesis of kerogen-rich geopressured sediments are predicted. Quartz deposition should occur at the top of the geopressured zone and decrease rapidly with increased depth as a result of the decreased flux of upward fluid flow with increased depth. Carbonate deposition should occur above the zone of CO₂ release from kerogen degradation as a result of the upward flux of CO₂ saturated fluids and subsequent decreases in fluid temperature, pressure and CO₂ solubility. Kaolinite-carbonate could deposit within and above the zone of CO₂ release from kerogen as a result of silicate dissolution by CO₂-rich acid pore fluids, followed by the potential for albite-carbonate deposition upon CO₂ depletion. In contrast, laumontite and anhydrite should not deposit during diagenesis of kerogen-rich geopressured sediments, but could deposit during diagenesis of normally-pressured or kerogen-poor geopressured sediments. An additional difference between these diagenetic environments is that quartz deposition would not be expected in normally-pressured sediments in which fluids are expected to be flowing downward. These mineralogic relationships compare favorably with observed relationships in the kerogen-rich geopressured sandstones of the Frio formation from the Texas Gulf Coast.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Sediment compaction.; Fluid dynamics.; Kerogen.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Norton, Denis

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleChemical equilibria and fluid flow during compaction diagenesis of organic-rich geopressured sediments.en_US
dc.creatorCapuano, Regina Marie.en_US
dc.contributor.authorCapuano, Regina Marie.en_US
dc.date.issued1988en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe effects of geopressuring and kerogen decomposition on mineral-fluid equilibria were calculated in order to predict the diagenetic-alteration mineralogy produced in equilibrium with kerogen-rich, geopressured sediments. These calculations indicate that several processes specific to kerogen-rich geopressured sediments contribute to the development of a characteristic alteration mineralogy. These processes are: (1) the upward flow of fluids in geopressured sediments, in contrast to the generally downward flow of fluids in normally-pressured sediments; (2) the coincidence of the depths of geopressuring (2-3 km; Fertl et al., 1976), with the geothermal temperatures necessary for CO₂ release (100°-135°C; Hunt, 1979), and CH₄ release (>90°C; Hunt, 1979); and (3) the opposing rates of sediment burial and CO₂ and CH₄ transfer into the upward-flowing fluids, which result in the geopressured pore fluids becoming enriched, and in some cases saturated, with respect to CO₂ and CH₄. Three patterns of mineral deposition during diagenesis of kerogen-rich geopressured sediments are predicted. Quartz deposition should occur at the top of the geopressured zone and decrease rapidly with increased depth as a result of the decreased flux of upward fluid flow with increased depth. Carbonate deposition should occur above the zone of CO₂ release from kerogen degradation as a result of the upward flux of CO₂ saturated fluids and subsequent decreases in fluid temperature, pressure and CO₂ solubility. Kaolinite-carbonate could deposit within and above the zone of CO₂ release from kerogen as a result of silicate dissolution by CO₂-rich acid pore fluids, followed by the potential for albite-carbonate deposition upon CO₂ depletion. In contrast, laumontite and anhydrite should not deposit during diagenesis of kerogen-rich geopressured sediments, but could deposit during diagenesis of normally-pressured or kerogen-poor geopressured sediments. An additional difference between these diagenetic environments is that quartz deposition would not be expected in normally-pressured sediments in which fluids are expected to be flowing downward. These mineralogic relationships compare favorably with observed relationships in the kerogen-rich geopressured sandstones of the Frio formation from the Texas Gulf Coast.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectSediment compaction.en_US
dc.subjectFluid dynamics.en_US
dc.subjectKerogen.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorNorton, Denisen_US
dc.contributor.committeememberLong, Austinen_US
dc.contributor.committeememberTitley, Spenceren_US
dc.contributor.committeememberInce, Simonen_US
dc.identifier.proquest8814220en_US
dc.identifier.oclc701107214en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.