Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635972
Title: Characterisation of salt diapir flanks constrained by field data
Author: Vargas Meleza, Liliana
ISNI:       0000 0004 5358 250X
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2014
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Abstract:
Marginal zones of salt diapirs and canopies are complex geological environments, with rapid spatial variations in lithology, strain, and fluid-assisted alteration. These complex zones can contain economically attractive hydrocarbon accumulations. However, they are difficult to image seismically due to the irregular geometry of salt bodies and the large property contrast between salt and the surrounding sediments. I present an integrated and multiscale approach to build realistic models of salt margins that represent the geological heterogeneity and seismic anisotropy in such complex zones. Structural field data and petrophysical measurements are used to constrain such models. A suite of evaporite samples of various compositions are used to predict the seismic anisotropy from their crystal preferred orientations (CPOs) and elastic properties. Ultrasonic seismic velocities are measured to calculate the relative contribution of the shape preferred orientations to the seismic anisotropy of such samples. Calculation of the seismic anisotropy produced by thinly interlayered evaporites provides a link between small-scale compositional heterogeneity with large-scale seismic anisotropy. Integration of outcrop structural models, petrophysical measurements and the characterisation of seismic anisotropy of salt is possible through seismic modelling. My results suggest that the seismic anisotropy of these samples is strongly controlled by their CPOs, which ranges from 3 to 7% for halite, from 8 to 10% for anhydrite, and from 13 to 22% for gypsum. Predictions indicate that the contribution of a small amount (< 10 %) of anhydrite can moderately alter the seismic anisotropy of polycrystalline evaporite. A small amount of anhydrite interlayered with halite yields anisotropy parameters with magnitudes of = −0.014, = −0.044, and = −0.193, which agree with those parameters calculated for polycrystalline salt. Such calculations of seismic anisotropy at grain scale enable the study of the propagation of seismic waves through salt margins. Seismic images generated from outcrop models of salt diapir flanks show moderate image degradation if anisotropy of salt is neglected during seismic migration. This methodology provides a foundation for the characterisation of seismic anisotropy of salt with which models of salt margins can be improved.
Supervisor: Not available Sponsor: National Council for Science and Technology of Mexico (Conacyt) ; Ministry of Energy of Mexico
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.635972  DOI: Not available
Keywords: Salt domes ; Seismic prospecting
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