Characterizing intrinsic and stratigraphic Q in VSP data with information measures

Lv, Siming

Characterizing intrinsic and stratigraphic Q in VSP data with information measures

dc.contributor.advisor	Innanen, Kris
dc.contributor.author	Lv, Siming
dc.contributor.committeemember	Lines, Laurence
dc.contributor.committeemember	Trad, Daniel
dc.date	2018-06
dc.date.accessioned	2018-01-19T00:51:43Z
dc.date.available	2018-01-19T00:51:43Z
dc.date.issued	2018-01-08
dc.description.abstract	Short-period multiples in finely layered geological media modify a seismic pulse as it propagates. This effect, called stratigraphic filtering, or extrinsic attenuation, is characterized by strong attenuation and dispersion of seismic amplitudes. It is similar to, and in fact very difficult to distinguish from, the effect produced by processes of seismic amplitude loss due to friction (or intrinsic attenuation). This is an important and difficult fact for interpreters of seismic data, because it means that similar data signatures are produced by very different geological and petrophysical features of the Earth. In this thesis I seek data analysis methods with the ability to amplify small differences produced by the processes of intrinsic attenuation and stratigraphic filtering, with the aim of discriminating between the two. In a zero-offset vertical seismic profiling (VSP) data set, at any instant in time we have access to a snapshot of the seismic wavefield along the principal direction of wave propagation. In practice, such a snapshot has the form of discrete amplitude values being assigned to each of a set of discrete depth values. Regarding this snapshot as a ``message'', made up of a sequence of ``letters'', or amplitude values, drawn from an ``alphabet'' of allowable amplitudes, permits the data to be analyzed using information-theoretic methods. For instance, Shannon entropy, which measures the degree of disorder within a message, can be assigned to each snapshot, and the time evolution of this number can be determined directly from a VSP data set. It is hypothesized that processes of intrinsic and extrinsic attenuation cause significant and measurable differences in the evolution of the entropy, which means this information measure could be utilized to help distinguish between the two. I analyze this with synthetic VSPs based on real well-log data, pointing out the important role of amplitude bin size in this information measure and the variability of results that should be expected as bin size changes. I point out with these examples that intrinsic and extrinsic attenuation processes tend to have opposite influences on entropy versus time curves. A field data set example is suggestive that the relative strength of stratigraphic filtering and intrinsic attenuation can be estimated in this way.	en_US
dc.identifier.citation	Lv, S. (2018). Characterizing intrinsic and stratigraphic Q in VSP data with information measures (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.	en_US
dc.identifier.doi	http://dx.doi.org/10.11575/PRISM/5359
dc.identifier.uri	http://hdl.handle.net/1880/106278
dc.language.iso	en	en_US
dc.publisher.faculty	Science	en_US
dc.publisher.institution	University of Calgary	en
dc.rights	University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.	en_US
dc.subject	Stratigraphic filtering	en_US
dc.subject	Shannon entropy	en_US
dc.subject	Seismic attenuation	en_US
dc.subject.classification	Education--Sciences	en_US
dc.subject.classification	Geophysics	en_US
dc.subject.classification	Statistics	en_US
dc.title	Characterizing intrinsic and stratigraphic Q in VSP data with information measures	en_US
dc.type	master thesis	en_US
thesis.degree.discipline	Geoscience	en_US
thesis.degree.grantor	University of Calgary	en_US
thesis.degree.name	Master of Science (MSc)	en_US
ucalgary.item.requestcopy	true
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