Homework No. 3 – Estimating Rock Strength from Geophysical Logs
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In this homework assignment, you will be estimating the unconfined compressive strength (UCS) as a function of depth using the porosity calculated from the Barnett data assuming full saturation of 1.0 g/cm3 water in pores and the density of a matrix of 2.7 g/cm3 in the first homework assignment as well as a sonic log from the same well. The sonic log contains compressional and shear velocities expressed as travel times in a unit of µs/ft versus depth for a section of the Barnett Shale well.
Utilize a program such as Matlab, Excel, R, or Python to follow the steps below. A CSV file of the sonic log and an Excel file of information of the depth range of each formation can be downloaded by clicking the right tab on the top of this page.
Use the following units in your plot: ‘ft’ for depth, and ‘psi’ for unconfined compressive strength.
I. Estimate UCS for the given depths using known empirical relations
G= 3KE
9K−E
2. Plot UCS estimated from the sonic log versus depth and plot UCS estimated from the density log versus depth. It is conventional to put depth on an inverted y-axis (increasing depth downward) and UCS on the x-axis.
doi:10.1017/CBO9780511586477
II. Answer the questions on the page below
