[CCoE Notice] Dissertation Defense: An investigation of static and dynamic data using multistage triaxial tests

[Grayson, Audrey A]

An investigation of static and dynamic data using multistage triaxial tests



Abdullah Bilal

Master’s Thesis



Defense Date: Thursday, April 28th 2016 Time: 3:00 pm Location: ERP Building 9, room 104

Committee Members: Dr. Michael Myers, Dr. Lori Hathon, Dr. John Dudley



                       The focus of this work is to develop an improved understanding of the relationship between static and dynamic data for a suite of four rock samples. “Static data” is defined as the large strain (> 10^-3) measurements on unloading and reloading tri-axial stress paths.  “Dynamic data” is the small strain (<10^-6) data acquired using standard acoustic velocity measurement techniques. The results are analyzed in term of Young’s Modulus and Poisson’s ratio. Quadratic fits have been applied to the static data on the unload and reload cycles. This allows us to separate the mechanisms present into a linear elastic term, M1, which we believe to be dominated by the contact modulus. M1 is shown to be constant throughout both the unload and reload cycles. M2 is the amplitude of the nonlinear elastic term. The magnitude of M2 is believed to be   due to the opening and closing of compliant pores. These interpretations result from the correlation we find between the linear term and the measured velocity and the nonlinear term with the measured irrecoverable strains. To our knowledge this is the first time the physical mechanisms behind the non-linear elastic response have been isolated.



                       Static to dynamic correlations are locally dependent on mineralogy and texture. For unconventional tight formations they depend on the total organic content (TOC) and thermal maturity. They also depend on porosity and clay content. Load bearing clays will increase irrecoverable strain and non-load bearing clays will impact velocity. Small amount of cements can significantly impact both static and dynamic data.  Static and dynamic data are typically obtained in the laboratory by measuring velocity while performing tri-axial tests. We also measure dynamic data using acoustic log measurements. These properties can be mapped and used in the reservoir simulation and 4D seismic models. They can also help us in predicting wellbore failure. Static and dynamic properties can help us perform better sand control in unconsolidated sands. The motivation behind this work is to predict rock strength properties like Young’s modulus and Poison’s ratio from acoustic log data.
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