High-Resolution Multi-Scale Reservoir Imaging and Monitoring

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Reservoir imaging and monitoring away from borehole are crucial for energy resource characterization and energy production optimization. I develop high-resolution, multi-scale imaging methods using active and passive data to characterize and monitor subsurface reservoir formations. At the meter scale, I develop a dipole sonic-waveform single-well imaging method based on dispersion analysis using Non-Linear Signal Comparison (NLSC) and Gaussian-beam migration to image fractures tens of meters away from borehole. At the kilometer scale, I use both three-component (3C) vertical-seismic profiling (VSP) and Distributed-Acoustic-Sensing VSP (DAS-VSP) data to image subsurface structures for geothermal reservoir characterization. For passive data, I develop a source-free logging method using borehole DAS ambient noise data to locate and monitor fractures. In Chapter II, I develop a new sonic-waveform imaging method and apply it to datasets from natural gas production wells. I then apply this method to sonic data collected at the Utah FORGE EGS (enhanced geothermal systems) site in Chapter III and data collected from the second EGS Collab testbed in Chapter IV. In Chapter V, I analyze 2D walkaway 3C-VSP geophone data and apply elastic-waveform inversion and reverse-time migration to obtain high-resolution images subsurface structures at the Raft River geothermal field. In Chapter VI, I apply a differential-phase spectral slope method to automatically pick first-arrival times on two zero-offset DAS-VSP gathers acquired at the Utah FORGE project site. I then analyze the DAS-VSP data and obtain velocity models and migration images of subsurface structures. Finally, I develop a source-free logging method using borehole DAS ambient noise data in Chapter VII. I compare borehole DAS ambient noise profiles with logging data and find that noise peaks correlate with fractured formations. I apply this method to monitor fractures during hydraulic stimulations at the first EGS Collab testbed in Chapter VIII and observe fractures opening, maintaining, and closing during stimulation. These multi-scale imaging and monitoring methods provide a suite of useful tools for detailed characterization of energy resources and optimization of energy production.

Borehole Geophysics, Imaging
Portions of this document appear in: David Li, Xiao Tian, Hao Hu, Xiao-Ming Tang, Xinding Fang, and Yingcai Zheng, (2020), "Gaussian beam imaging of fractures near the wellbore using sonic logging tools after removing dispersive borehole waves," GEOPHYSICS 85: D133-D143. https://doi.org/10.1190/geo2019-0104.1; and in: Li, D., Huang, L., Chi, B., Gao, K., Jones, C., Moore, J., & Zheng, Y. (2021). Elastic-waveform inversion and imaging of 2010 walkaway VSP data from the Raft River geothermal field. Geothermics, 94, 102095; and in: Li, D., Huang, L., Zheng, Y., Li, Y., Wannamaker, P., & Moore, J. (2022). Feasibility of source-free DAS logging for next-generation borehole imaging. Scientific Reports, 12(1), 11910.