Monitoring Fracture Saturation With Internal Seismic Sources and Twin Neural Networks

Journal Article · 26 January 2022 · Journal of Geophysical Research. Solid Earth

DOI: https://doi.org/10.1029/2021jb023005 · OSTI ID:1864814

Nolte, D. D.  ^[1]; Pyrak‐Nolte, L. J.  ^[2]

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1. Purdue Univ., West Lafayette, IN (United States); Purdue University
2. Purdue Univ., West Lafayette, IN (United States)

Seismic coda-wave analysis is a well-developed method for detecting subtle physical changes in complex media by measuring arrival times in the late-arriving energy from multiply scattered or reflected waves. However, a challenge arises when multiply scattered waves are not sufficiently separated in time from the direct arrivals to provide a clear coda wave train. Additional complications for monitoring changes in fracture systems arise when the signals originate from unsynchronized internal sources, such as natural or induced seismicity, from acoustic emission, or from transportable intra-fracture sources (chattering dust), that generate uncontrolled signals that vary in arrival time, amplitude and frequency content. Here, we use a twin neural network (TNN also known as a Siamese neural network) for dimensionality reduction to analyze signals from chattering dust to classify the fluid saturation state of a synthetic fracture system. The TNN with shared weights generates a low-dimensional representation of the data input by minimizing contrastive loss, serving as the input to a multiclass classifier that accurately classifies whether multiple fractures in a fracture system are fully saturated or partially saturated, or whether a change in saturation has occurred in different fractures in the system. Furthermore, these results show that information buried in unresolved codas from uncontrolled sources can be extracted using machine learning to monitor the evolution of fracture systems caused by physical and chemical processes even when the scattered and direct wave fields overlap.

• Research Organization: Purdue Univ., West Lafayette, IN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division
• Grant/Contract Number: SC0001048
• OSTI ID: 1864814
• Journal Information: Journal of Geophysical Research. Solid Earth, Journal Name: Journal of Geophysical Research. Solid Earth Journal Issue: 2 Vol. 127; ISSN 2169-9313
• Publisher: American Geophysical UnionCopyright Statement
• Country of Publication: United States
• Language: English