Preprint Article Version 3 Preserved in Portico This version is not peer-reviewed

Investigation of the Time-Lapse Changes with the DAS Borehole Data at the Brady Geothermal Field Using Deconvolution Interferometry

Version 1 : Received: 30 April 2021 / Approved: 3 May 2021 / Online: 3 May 2021 (16:42:03 CEST)
Version 2 : Received: 26 June 2021 / Approved: 29 June 2021 / Online: 29 June 2021 (11:49:00 CEST)
Version 3 : Received: 5 November 2021 / Approved: 8 November 2021 / Online: 8 November 2021 (13:15:26 CET)

How to cite: Chang, H.; Nakata, N. Investigation of the Time-Lapse Changes with the DAS Borehole Data at the Brady Geothermal Field Using Deconvolution Interferometry. Preprints 2021, 2021050014 (doi: 10.20944/preprints202105.0014.v3). Chang, H.; Nakata, N. Investigation of the Time-Lapse Changes with the DAS Borehole Data at the Brady Geothermal Field Using Deconvolution Interferometry. Preprints 2021, 2021050014 (doi: 10.20944/preprints202105.0014.v3).

Abstract

The distributed acoustic sensing (DAS) has great potential for monitoring natural-resource reservoirs and borehole conditions. However, the large volume of data and complicated wavefield add challenges to processing and interpretation. In this study, we demonstrate that seismic interferometry based on deconvolution is a convenient tool for analyzing this complicated wavefield. We extract coherent wave from the observation of a borehole DAS system at the Brady geothermal field in Nevada. Then, we analyze the coherent reverberating waves, which are used for monitoring temporal changes of the system. These reverberations are tirelessly observed in the vertical borehole DAS data due to cable or casing ringing. The deconvolution method allows us to examine the wavefield at different boundary conditions. We interpret the deconvolved wavefields using a simple 1D string model. The velocity of this wave varies with depth, observation time, temperature, and pressure. We find the velocity is sensitive to disturbances in the borehole related to increasing operation intensity. The velocity decreases with rising temperature, which potentially suggests that the DAS cable or the casing are subjected to high temperature. This reverberation can be decomposed into distinct vibration modes in the spectrum. We find that the wave is dispersive, and the the fundamental mode propagate with a large velocity. The method can be useful for monitoring borehole conditions or reservoir property changes. For the later, we need better coupling than through only friction in the vertical borehole to obtain coherent energy from the formation.

Keywords

Distributed Acoustic Sensing; Borehole; Time-Lapse

Subject

EARTH SCIENCES, Geophysics

Comments (1)

Comment 1
Received: 8 November 2021
Commenter: Hilary Chang
Commenter's Conflict of Interests: Author
Comment: In this revised version, we have added explanations on the connection between this study and relevant research in the introduction (Section 1). We omit the details of the results that have been investigated in previous studies (Section 2). We reorder the structure of the results (Section 3) and emphasize the novelty of our technique and results. These changes make the manuscript more concise so the readers can focus on the main points.
+ Respond to this comment

We encourage comments and feedback from a broad range of readers. See criteria for comments and our diversity statement.

Leave a public comment
Send a private comment to the author(s)
Views 0
Downloads 0
Comments 1
Metrics 0


×
Alerts
Notify me about updates to this article or when a peer-reviewed version is published.
We use cookies on our website to ensure you get the best experience.
Read more about our cookies here.