Surface-wave tomography of Yucca Flat Nevada
Abstract not provided.
Publications
Geophysical Monitoring and Imaging
Abstract not provided.
Insights into seasonal active layer dynamics by monitoring relative velocity changes using ambient seismic noise
Abstract not provided.
Experiment design study in 3D DC resistivity: Adjoint sensitivities in a horizontal steel-cased borehole
Abstract not provided.
The DC Response Of Electrically Conducting Fractures Excited By A Grounded Current Source
Abstract not provided.
PALSIE: Permafrost Active-Layer Seismic Experiment
Abstract not provided.
Integrated Geomechanics and Geophysics in Induced Seismicity: Trigger Physics
Abstract not provided.
Geophysics Capabilities Brief
Abstract not provided.
Self-tuning Seismic Sensors: Real-time Trigger Level Adjustments
Abstract not provided.
Monitoring Active Layer Freeze/Thaw Using Seismic Noise
Abstract not provided.
Imaging Fracture Networks Using Joint Seismic and Electrical Change Detection Techniques
Abstract not provided.
The direct-current response of electrically conducting fractures excited by a grounded current source
Geophysics
Hydraulic fracture stimulation of low permeability reservoir rocks is an established and cross-cutting technology for enhancing hydrocarbon production in sedimentary formations and increasing heat exchange in crystalline geothermal systems. Whereas the primary measure of success is the ability to keep the newly generated fractures sufficiently open, long-term reservoir management requires a knowledge of the spatial extent, morphology, and distribution of the fractures-knowledge primarily informed by microseismic and ground deformation monitoring. To minimize the uncertainty associated with interpreting such data, we investigate through numerical simulation the usefulness of direct-current (DC) resistivity data for characterizing subsurface fractures with elevated electrical conductivity by considering a geophysical experiment consisting of a grounded current source deployed in a steel cased borehole. In doing so, the casing efficiently energizes the fractures with steady current. Finite element simulations of this experiment for a horizontal well intersecting a small set of vertical fractures indicate that the fractures manifest electrically in (at least) two ways: (1) a local perturbation in electric potential proximal to the fracture set, with limited farfield expression and (2) an overall reduction in the electric potential along the borehole casing due to enhanced current flow through the fractures into the surrounding formation. The change in casing potential results in a measurable effect that can be observed far from fractures themselves. Under these conditions, our results suggest that farfield, timelapse measurements of DC potentials can be interpreted by simple, linear inversion for a Coulomb charge distribution along the borehole path, including a local charge perturbation due to the fractures. This approach offers an inexpensive method for detecting and monitoring the time-evolution of electrically conducting fractures while ultimately providing an estimate of their effective conductivity - the latter providing an important measure independent of seismic methods on fracture shape, size, and hydraulic connectivity.
SPE5 Far-field Waveform Predictions Using Full Waveform Inversion
Abstract not provided.
Adaptive Self-Tuning Networks
Abstract not provided.
Challenges for Adaptive Self-Tuning of Seismic Sensors: Detailed Case Study at Erebus Volcano Antarctica
Abstract not provided.
Full waveform source inversions for SPE data: results challenges and lessons learned
Abstract not provided.
Imaging Fracture Networks Using Joint Seismic and Electrical Change Detection Techniques ? An Example Of Subsurface Imaging
Abstract not provided.
Permafrost Active Layer Seismic Interferometry Experiment (PALSIE) and satellite observations
Abstract not provided.
Geophysics Capabilities Brief
Abstract not provided.
Permafrost Active Layer Seismic Interferometry Experiment (PALSIE)
We present findings from a novel field experiment conducted at Poker Flat Research Range in Fairbanks, Alaska that was designed to monitor changes in active layer thickness in real time. Results are derived primarily from seismic data streaming from seven Nanometric Trillium Posthole seismometers directly buried in the upper section of the permafrost. The data were evaluated using two analysis methods: Horizontal to Vertical Spectral Ratio (HVSR) and ambient noise seismic interferometry. Results from the HVSR conclusively illustrated the method's effectiveness at determining the active layer's thickness with a single station. Investigations with the multi-station method (ambient noise seismic interferometry) are continuing at the University of Florida and have not yet conclusively determined active layer thickness changes. Further work continues with the Bureau of Land Management (BLM) to determine if the ground based measurements can constrain satellite imagery, which provide measurements on a much larger spatial scale.
Experiment design study in 3d dc resistivity: Adjoint sensitivities in a horizontal steel-cased borehole
SEG Technical Program Expanded Abstracts
We investigate a novel application of Fŕechet derivatives for time-lapse mapping of deep, electrically-enhanced fracture systems with a borehole to surface DC resistivity array. The simulations are evaluated for a cased horizontal wellbore embedded in a homogeneous halfspace, where measurements are evaluated near, mid-range, and far from the well head. We show that, in all cases, measurements are sensitive to perturbations centered on the borehole axis and that the sensitivity volume decreases as a function of increased measurement offset from the well head. The sensitivity analysis also illustrates that careful consideration must be taken when developing an electrical survey design for these scenarios. Specifically, we show that positive perturbations in earth conductivity near the wellbore can manifest as both positive and negative measurement perturbations, depending on where the measurement is taken. Furthermore, we show that the transition between the regions along the wellbore of positive and negative contribution results in a "pinch point", representing a region along the wellbore where a given surface measurement is blind to any changes or enhancement of electrical conductivity.
High energy stimulations imaged with geophysical change detection techniques
Transactions - Geothermal Resources Council
During the initial phase of this Department of Energy (DOE) Geothermal Technologies Office (GTO) SubTER project, we conducted a series of high-energy stimulations in shallow wells, the effects of which were evaluated with high resolution seismic imaging campaigns designed to characterize induced fractures. The high-energy stimulations use a novel explosive source that limits damage to the borehole, which was paramount for change detection seismic imaging and re-fracturing experiments. This work provided evidence that the high-energy stimulations were generating self-propping fractures and that these fracture locations could be imaged at inch scales using high-frequency seismic tomography. While the seismic testing certainly provided valuable feedback on fracture generation for the suite of explosives, it left many fracture properties (i.e. permeability) unresolved. We present here the methodology for the second phase of the project, where we are developing and demonstrating emerging seismic and electrical geophysical imaging technologies that have been designed to characterize 1) the 3D extent and distribution of fractures stimulated from the explosive source, 2) 3D fluid transport within the stimulated fracture network through use of a contrasting tracer, and 3) fracture attributes through advanced data analysis. Focus is being placed upon advancing these technologies toward near real-time acquisition and processing in order to help provide the feedback mechanism necessary to understand and control fracture stimulation and fluid flow.
Imaging fracture networks using joint seismic and electrical change detection techniques
50th US Rock Mechanics / Geomechanics Symposium 2016
During the initial phase of this SubTER project, we conducted a series of high resolution seismic imaging campaigns designed to characterize induced fractures. Fractures were emplaced using a novel explosive source that limits damage to the borehole. This work provided evidence that fracture locations could be imaged at inch scales using high-frequency seismic tomography but left many fracture properties (i.e. permeability) unresolved. We present here the methodology for the second phase of the project, where we will develop and demonstrate emerging seismic and electrical geophysical imaging technologies that characterize 1) the 3D extent and distribution of fractures stimulated from the explosive source, 2) 3D fluid transport within the stimulated fracture network through use of a contrasting tracer, and 3) fracture attributes through advanced data analysis. Focus will be placed upon advancing these technologies toward near real-time acquisition and processing in order to help provide the feedback mechanism necessary to understand and control fracture stimulation and fluid flow.
Adaptive Self-Tuning Networks
Abstract not provided.
Full waveform inversion methods for source and media characterization before and after SPE5
Abstract not provided.
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