Young's Elastic Modulus: Comparing the dynamic and static approaches using standard and defect-model correlation methods

Obinna Muozube

Research output: ThesisMaster's Thesis

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Abstract

This thesis presents the correlation results of static and dynamic Young’s moduli based on standard and simplified defect-model approaches for some rock intervals at two different locations. Elastic properties of rocks can be determined in two ways; either by in-situ seismic velocity measurements accomplished by logging in a borehole, or by compressive tests carried out on sample cores drawn from such borehole. The first method defines the dynamic Young’s modulus determination, and the later defines the static method. However, these two measurement methods do not give the same results or values. Studies have shown that the difference in values stems from their differential strain amplitude. While the strain amplitude of static Young’s moduli is in the order of 10-3 to 10-2, that of the dynamic Young’s moduli is much smaller and in the order of 10-7 to 10-6. Therefore, conventional practices has been applied over time in finding correlations between the two, so that whenever one with easier and cheaper means of measurement is estimated, the other could be derived based on the established correlations. Recently, the focus shifted to removing or correcting for factors that brings about disparity in measured values of the two properties. So that a singular measurement using either of the methods could approximate or equal the other. One of such correction is the application of the simplified defect model. This model tends to compensate or rather improve the in-situ static (Young’s modulus) estimates with respect to the contributions of defects such as fractures, microcracks and intergranular boundaries. These defects tend to close up in laboratory measurements giving higher laboratory values that yield lower in-situ static estimates. Hence, this thesis not only compares measured values of the two elastic properties and their standard correlations, but also discusses the application of the aforementioned model on available log data.
Translated title of the contributionYoung's Elastic Modulus: Vergleich der dynamischen und statischen Ansätze unter Verwendung von Standard- und Defektmodell- Korrelationsverfahren
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Scholger, Robert, Supervisor (internal)
Award date12 Apr 2019
Publication statusPublished - 2019

Bibliographical note

embargoed until null

Keywords

  • Young's modulus
  • static Young's modulus
  • dynamic Young's modulus
  • standard static and dynamic correlations
  • simplified defect model correlations
  • uniaxial compressive tests
  • velocity measurements
  • full wave sonic logs
  • isolated ultrasonic measurement
  • optical borehole image logs
  • regression plots
  • log traces
  • tangent-modulus method
  • stress-strain curve
  • loading and unloading sessions

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