High‐Resolution Ambient Noise Imaging of Geothermal Reservoir Using 3C Dense Seismic Nodal Array and Ultra‐Short Observation

Abstract

Geothermal energy is one of the most promising renewable energy sources, particularly within the context of China's energy structure optimization, environmental protection measures, energy conservation, and rising pressure on emission reduction. By the end of 2020, renewable energy facilities, including solar, wind, geothermal and other types of energy, in China will supply 27% of total power generation, according to the government's 2016-2020 plan for renewable energy. However, geothermal resources accounted for only 0.6

Artifacts in high-frequency surface wave dispersion imaging

“…Unfortunately, we find it is challenging to fully remove these spikes on dispersion spectra, since they are likely associated with some persistent noise sources around the site. Similar phenomenon has been reported in the literatures (e.g., Zeng and Ni, 2010;Gaudot et al, 2016;Cheng et al, 2021b).…”

“…Ambient noise interferometry estimates Green's functions between cross-correlation of two receivers from the ambient seismic field (Shapiro and Campillo, 2004;Snieder, 2004;Wapenaar, 2004;Bensen et al, 2007;Snieder et al, 2009;Nakata et al, 2015;Paitz et al, 2019;Tsai and Sager, 2022). This approach has been applied to characterize multiple scales of earth structure: from global or continental scale deep-structure imaging in seismology (e.g., Yang et al, 2007;Lin et al, 2008;Yao and van der Hilst, 2009;Lin et al, 2009;Strobbia and Cassiani, 2011;Tibuleac and von Seggern, 2012;Becker and Knapmeyer-Endrun, 2018;Chen et al, 2021;Xu et al, 2022) to local scale exploration (e.g., Bakulin and Calvert, 2006;Wapenaar et al, 2008;Draganov et al, 2009;Nakata et al, 2011;Ali et al, 2013;Behm et al, 2014;Nakata et al, 2016;Behm et al, 2016;Castellanos et al, 2020;Cheng et al, 2021b). During the last decade, ambient noise interferometry has also found a variety of applications in the near-surface characterization domain (e.g., Foti et al, 2011;O'Connell and Turner, 2011;Xu et al, 2013;Cheng et al, 2015;Shirzad et al, 2015;Foti et al, 2018;Dou et al, 2017;Cheng et al, 2018a;Cárdenas-Soto et al, 2021;…”

Using Dark Fiber and Distributed Acoustic Sensing to Characterize a Geothermal System in the Imperial Valley, Southern California

“…This combination of spatial stacking and temporal decimation reduced the dataset size by about a factor of 25. Next, a classical ambient noise data preprocessing workflow (e.g., Bensen et al, 2007;Cheng et al, 2015Cheng et al, , 2021a was applied to the continuous DAS dataset (2 days) by processing 1 minute non-overlapping data segments with the native recording unit (strain rate). Preprocessing steps included mean and trend removal, as well as a symmetric Hanning taper applied to each end of the time series, followed by temporal and spectral normalization.…”

“…To extract empirical Green's function (EGF) from the preprocessed ambient noise dataset, we utilized the cross-coherence algorithm by performing cross-correlation followed with spectral whitening (Schuster et al, 2004;Prieto et al, 2009;Nakata et al, 2011). According to Cheng et al (2021a), the cross-coherence algorithm has advantages over the cross-correlation algorithm for mitigating pseudo-arrivals associated with spectral spikes and improving the signal to noise ratio (SNR) of the resulting EGF. After cross-coherence, we employ phase-weighted stacking (PWS) on 2 days of EGFs to further improve the coherent signals (Schimmel & Paulssen, 1997;Schimmel et al, 2011;Ventosa et al, 2017).…”

“…Following the pioneering work of Campillo and Paul (2003), ambient noise interferometry can be used to estimate an empirical Green's function (EGF) between two receivers by cross-correlating the ambient seismic wave field (Shapiro & Campillo, 2004;Snieder, 2004;Wapenaar, 2004;Bensen et al, 2007;Snieder et al, 2009;Nakata et al, 2015;Cheng et al, 2016Cheng et al, , 2018Behm et al, 2019;Fichtner et al, 2020). In recent years, ambient noise interferometry techniques have found a variety of applications for geothermal reservoir imaging by using dense nodal arrays (e.g., Lehujeur et al, 2018;Spica et al, 2018;Martins et al, 2019Martins et al, , 2020Planès et al, 2020;Zhou et al, 2021;Cheng et al, 2021a). Recorded EGFs are often rich in surface wave energy, hence the most commonly retrieved physical property from ambient noise studies are shear wave velocities estimated using surface wave tomography methods.…”