[CCoE Notice] PhD Defense announcement and advertisement

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[Dissertation Defense Announcement at the Cullen College of Engineering]

The Petroleum Engineering Department Presents



Modeling the Compressional Velocity of Unconventional Reservoirs Using High Resolution Scanning Acoustic Microscope Measurements



Alessandra Simone

November 22, 2022; 10:00 AM - 12:00 PM (CST)
Location: Technology Bridge Building 9, Classroom 124

Committee Chair:
Dr. Michael T. Myers

Committee Members:
Dr. Lori Hathon | Dr. Christine Ehlig-Economides | Dr. Rob Stewart | Dr. Ron Bonnie

Abstract

Acoustic properties are a critical component of unconventional reservoir characterization. Studies that have examined organic rich shale properties at multiple scales have successfully correlated kerogen content and thermal maturity with compressional velocities and anisotropy variations. As maturity increases, kerogen is thermally altered to bitumen and the location of organic material shifts from predominantly load bearing, bedding plane parallel oriented laminae to interparticle pores, resulting in distinct changes in the acoustic velocity and observed anisotropy. In the absence of sonic logs, synthetic compressional velocities can be derived from individual constituent (i.e. acoustic microfacies) using a staged differential effective medium model (SDEM). Through the application of SDEM, successful proof of concept is achieved for Scanning Acoustic Microscopy high-resolution acoustic velocity measurements in unconventional rocks, where the wavelength dimensions are larger than individual grains and pores, eliminating the need for ray tracing.

Scanning Acoustic Microscopy (SAM) is an advanced form of non-destructive testing that employs high-frequency (20-50 MHz) ultrasound to generate acoustic images. The two-way travel time of planar longitudinal waves is measured in uniformly cut 2 mm thick samples. Individual waveforms are recorded at each grid location (50 *m pixel size). Variations in acoustic pulse arrival time at the sample/stage interface relates to variations in acoustic impedance. The pulse arrival time is used to generate a compressional velocity (Vp) map to characterize each distinct acoustic microfacies.

The presence and distribution of organic material is identified using Scanning Electron Microscopy -SEM- and Energy Dispersive Spectroscopy -EDS-. Core plugs are first micro-CT scanned and plug acoustic velocities are measured as received. Thin sections and SAM discs are prepared and processed. Resulting SAM velocity maps are used to select SEM sites for acoustic microfacies characterization. Samples are ion milled. Back Scatter Electron (BSE) imaging is used for characterization of organic content and mineralogy. Energy dispersive x-ray (EDS) mapping is used for differentiation of mineral phases. Segmented volumes of porosity, TOC, and mineral phases are used for qualitative differentiation of microfacies. High resolution Vp is input into the SDEM and resulting synthetic compressional velocities are in agreement with standard plug Vp measurements.

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