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Pressure solution and microfracturing in primary oil migration, upper cretaceous Austin Chalk, Texas Gulf Coast
dc.creator | Chanchani, Jitesh | |
dc.date.accessioned | 2012-06-07T22:35:50Z | |
dc.date.available | 2012-06-07T22:35:50Z | |
dc.date.created | 1994 | |
dc.date.issued | 1994 | |
dc.identifier.uri | https://hdl.handle.net/1969.1/ETD-TAMU-1994-THESIS-C4544 | |
dc.description | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. | en |
dc.description | Includes bibliographical references. | en |
dc.description.abstract | The Upper Cretaceous Austin Chalk is a well known source rock and fractured reservoir. Production is mainly from fractures, and the mechanism by which oil migrates from the matrix into the fractures is not well understood. Microfracturing due to oil generation offers a possible explanation for the mechanism of the primary migration of oil in the Austin Chalk. Detailed petrographic analysis was undertaken to study the primary migration of oil in the Austin Chalk. The important components of the primary migration system are the solution seams, swarms of horizontal microfractures associated with the solution seams and the tectonic fractures from which the oil is recovered. Pressure solution is manifest in the Austin Chalk as millimeter-scale solution seams and smaller microseams. The solution seams are composites formed by the superposition of the microseams in an anastomosing network. Evidence for pressure solution is the presence of truncated fossils along seams and the high concentration of insolubles within them. A significant amount of organic matter and bitumen was observed to be concentrated within the seams. Associated with the solution seams are swarms of horizontal microftactures, many of them filled with calcite. Numerous vertical, tectonic fractures are found intersecting the solution seams. Pressure solution serves to concentrate organic matter within the solution seams and oil is generated here. It is postulated that the accompanying increase in fluid volume raises the pore pressures and fractures the rock. These newly created microfractures are avenues for migration of fluids from the seams. It is likely that oil migrates from the seams into the tectonic fractures via the microftactures. Oil may also be migrating directly from the seams into the fractures along an organic network. The matrix recharges the fractures by the mechanism postulated in this study. Thus, production can be sustained at low rates even after the initial period of decline. Further studies should attempt to correlate the carbonate in the matrix with that in the microfractures, and the oil in the seams with that in the fractures. | en |
dc.format.medium | electronic | en |
dc.format.mimetype | application/pdf | |
dc.language.iso | en_US | |
dc.publisher | Texas A&M University | |
dc.rights | This thesis was part of a retrospective digitization project authorized by the Texas A&M University Libraries in 2008. Copyright remains vested with the author(s). It is the user's responsibility to secure permission from the copyright holder(s) for re-use of the work beyond the provision of Fair Use. | en |
dc.subject | geology. | en |
dc.subject | Major geology. | en |
dc.title | Pressure solution and microfracturing in primary oil migration, upper cretaceous Austin Chalk, Texas Gulf Coast | en |
dc.type | Thesis | en |
thesis.degree.discipline | geology | en |
thesis.degree.name | M.S. | en |
thesis.degree.level | Masters | en |
dc.type.genre | thesis | en |
dc.type.material | text | en |
dc.format.digitalOrigin | reformatted digital | en |
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