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Chapter 2





             Unsupervised clustering


             methods for noninvasive
             characterization of


             fracture-induced
             geomechanical alterations




             Siddharth Misra*, Aditya Chakravarty*, Pritesh Bhoumick †,a  and
             Chandra S. Rai ‡
             *
              Harold Vance Department of Petroleum Engineering, Texas A&M University, College Station,
                         †
                                                                  ‡
             TX, United States, PricewaterhouseCoopers (PwC), Houston, TX, United States, The University
             of Oklahoma, Norman, OK, United States
               Chapter outline
                1 Introduction           39   6 Results and discussions  53
                2 Objective of this study  41   6.1 Effect of feature engineering 53
                3 Laboratory setup and          6.2 Effect of clustering method  55
                  measurements           41     6.3 Effect of dimensionality
                4 Clustering methods for the       reduction            57
                  proposed noninvasive          6.4 Effect of using features
                  visualization of geomechanical   derived from both prefracture
                  alterations            44        and postfracture waveforms  58
                  4.1 K-means clustering  44  7 Physical basis of the fracture-
                  4.2 Hierarchical clustering  45  induced geomechanical
                  4.3 DBSCAN             47     alteration index        59
                5 Features/attributes for the  8 Conclusions            61
                  proposed noninvasive        Acknowledgments           62
                  visualization of geomechanical  Declarations          62
                  alteration             48   References                62
                  5.1 Feature engineering  49
                  5.2 Dimensionality reduction  52





             a
              Present address: Pricewaterhouse Coopers, Houston, TX, United States.
             Machine Learning for Subsurface Characterization. https://doi.org/10.1016/B978-0-12-817736-5.00006-5
             © 2020 Elsevier Inc. All rights reserved.                    39
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