Show simple item record

dc.contributor.advisorBenson, Robert D.
dc.contributor.authorBailey, Austin
dc.date.accessioned2017-06-16T16:50:55Z
dc.date.accessioned2022-02-03T13:01:31Z
dc.date.available2017-06-16T16:50:55Z
dc.date.available2022-02-03T13:01:31Z
dc.date.issued2017
dc.identifierT 8291
dc.identifier.urihttps://hdl.handle.net/11124/171016
dc.descriptionIncludes bibliographical references.
dc.description2017 Spring.
dc.description.abstractAmplitude Variation with Angle and Azimuth (AVAZ) is a method that examines the azimuthal change in seismic amplitude to calculate the anisotropy of a horizontally transverse isotropic (HTI) formation. Anisotropy is generally indicative of heterogeneity in the rock fabric, be it fractures, crack-like pores, or local stress changes. The aim of this study as a whole is to examine the relationship between AVAZ anisotropy magnitude from seismic data and pore pressure gradient from wells. Pore pressure is an important reservoir metric that is often used to understand the production variations within a hydrocarbon reservoir. Predicting pore pressure from seismic data can be extremely useful in not only estimating production, but also in predicting the completion and development strategies that may be most effective. However, seismic-based pore pressure prediction methods have not evolved much in the past decade, with the industry standard to rely on the Bowers (1995) or Eaton (1987) method of converting seismic velocities to pore pressure volumes. These methods may fall short as a predictive tool in many cases, due to their lack of spatial resolution and dependency on a stable velocity model, which may not always be available. Therefore, this study was begun in order to examine if an alternative method of detecting pore pressure variations could be found using AVAZ. The AVAZ methodology was applied to a merged 3D seismic dataset in the Anadarko Basin, Oklahoma provided by Cimarex Energy, in order to examine the Woodford Shale. The Woodford has been a key player in hydrocarbon production from the Anadarko Basin for decades, mainly serving as a source rock until the mid-2000's during the ``unconventional revolution''. Throughout its extent, the Woodford Formation shows significant heterogeneity due to both the structure and faults of the basin, as well as changes in the rock fabric. This study aims to use the AVAZ methodology to examine heterogeneity in the Woodford and to relate its anisotropy to pore pressure. Before examining the AVAZ effect in the seismic data, forward modeling from well logs was completed to conceptualize a relationship between pore pressure and anisotropy. Theoretically, at higher pore pressures the reservoir fluid may be effectively propping the fractures open, thus having a greater effect on any pressure wave traveling through the fluid. At lower pore pressure, the overburden pressure dominates the fluid-filled fractures and closes them down. Therefore, at higher pore pressure the AVAZ anisotropy would be greater than at lower pore pressure. The forward modeling from dipole sonic well logs confirms this conceptual model by showing a positive relationship between pore pressure and AVAZ anisotropy. Before the results of the AVAZ workflow were obtained, a variety of pre-processing steps and quality controls were done on the merged 3D seismic dataset. Although the pore pressure - anisotropy relationship appears robust in modeling, the AVAZ results from the seismic data do not appear to correlate with pore pressure. It is likely that acquisition-related artifacts in the seismic data, as well as small magnitude of change in pore pressure, contribute to this lack of correlation. However, further interpretation of the AVAZ volumes shows local stress variations near faults as well as a potential secondary stress trend striking to the north-east. Such information has implications for completion and overall development of the Woodford as an unconventional resource play.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2017 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjectfractures
dc.subjectshale reservoirs
dc.subjectunconventional
dc.subjectreservoir characterization
dc.subjectanisotropy
dc.subjectstress
dc.titleExamination of anisotropy using Amplitude Variation with Angle and Azimuth (AVAZ) in the Woodford Shale, Anadarko Basin, Oklahoma
dc.typeText
dc.contributor.committeememberRoche, Steven L.
dc.contributor.committeememberTrainor-Guitton, Whitney
dc.contributor.committeememberWood, Lesli J.
thesis.degree.nameMaster of Science (M.S.)
thesis.degree.levelMasters
thesis.degree.disciplineGeophysics
thesis.degree.grantorColorado School of Mines


Files in this item

Thumbnail
Name:
Bailey_mines_0052N_11272.pdf
Size:
13.24Mb
Format:
PDF

This item appears in the following Collection(s)

Show simple item record