How Different Are Ultrasonic Lab and Wireline Measurements in the Estimation of Dynamic Elastic Moduli?

Abstract

Acoustic measurements are vital for geomechanical applications to design safe mud weight window, estimating rock strength parameters, sand control, hydraulic fracturing, etc. There is usually a discrepancy between the ultrasonic lab and sonic log measurements due to the frequency difference and other measurement conditions. This work investigates the discrepancy between the ultrasonic lab measurements and sonic logs of both shear wave velocity (Vs) and compressional wave velocity (Vp) to understand the pivotal effect of these measurements on the accuracy of estimating dynamic moduli. Core samples for three zones (Nahr Umr shale, Zubair shale, and Zubair sandstone) in Rumaila field, Iraq, and well logs for the same sections were employed in this investigation. Single stage triaxial tests equipment used to measure Vp and Vs. Then, dynamic elastic rock properties were estimated using the data of ultrasonic lab and wireline measurements. The results illustrated that the readings of the velocities of sonic log waves are remarkably less than the measurements of the velocities of ultrasonic lab waves. This discrepancy can be explained due to the frequency in the laboratory to measure both dynamic wave velocities is too high when comparing it to the frequency of both dynamic wave velocities of the sonic log, besides other factors such as temperature and pressure conditions in the ambient lab and the downhole environments. For the laboratory (ultrasonic), the frequency is approximately one million hertz. However, for the sonic log, the frequency is approximately 20,000 hertz. Consequently, the estimations of the dynamic elastic moduli were tangibly different for both approaches. The least influenced elastic moduli by the discrepancy between sonic log and ultrasonic lab measurements was the bulk modulus (K).

Department(s)

Geosciences and Geological and Petroleum Engineering

Comments

3M, Grant None

International Standard Book Number (ISBN)

978-171383912-5

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 American Rock Mechanics Association, All rights reserved.

Publication Date

01 Jan 2021

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