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Statistical methods of fracture characterization using acoustic borehole televiewer log interpretation

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journal contribution
posted on 10.02.2021, 22:11 by C Massiot, John Townend, A Nicol, DD McNamara
©2017. American Geophysical Union. All Rights Reserved. Acoustic borehole televiewer (BHTV) logs provide measurements of fracture attributes (orientations, thickness, and spacing) at depth. Orientation, censoring, and truncation sampling biases similar to those described for one-dimensional outcrop scanlines, and other logging or drilling artifacts specific to BHTV logs, can affect the interpretation of fracture attributes from BHTV logs. K-means, fuzzy K-means, and agglomerative clustering methods provide transparent means of separating fracture groups on the basis of their orientation. Fracture spacing is calculated for each of these fracture sets. Maximum likelihood estimation using truncated distributions permits the fitting of several probability distributions to the fracture attribute data sets within truncation limits, which can then be extrapolated over the entire range where they naturally occur. Akaike Information Criterion (AIC) and Schwartz Bayesian Criterion (SBC) statistical information criteria rank the distributions by how well they fit the data. We demonstrate these attribute analysis methods with a data set derived from three BHTV logs acquired from the high-temperature Rotokawa geothermal field, New Zealand. Varying BHTV log quality reduces the number of input data points, but careful selection of the quality levels where fractures are deemed fully sampled increases the reliability of the analysis. Spacing data analysis comprising up to 300 data points and spanning three orders of magnitude can be approximated similarly well (similar AIC rankings) with several distributions. Several clustering configurations and probability distributions can often characterize the data at similar levels of statistical criteria. Thus, several scenarios should be considered when using BHTV log data to constrain numerical fracture models.

History

Preferred citation

Massiot, C., Townend, J., Nicol, A. & McNamara, D. D. (2017). Statistical methods of fracture characterization using acoustic borehole televiewer log interpretation. Journal of Geophysical Research: Solid Earth, 122(8), 6836-6852. https://doi.org/10.1002/2017JB014115

Journal title

Journal of Geophysical Research: Solid Earth

Volume

122

Issue

8

Publication date

01/08/2017

Pagination

6836-6852

Publisher

American Geophysical Union (AGU)

Publication status

Published

Online publication date

26/08/2017

ISSN

2169-9313

eISSN

2169-9356

Language

en

Exports