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In June 2009, the New York Times published an article about the public fear of geothermal development causing earthquakes. The article highlighted a project funded by the U.S. Department of Energy's (DOE) Geothermal Technologies Program bringing power production at The Geysers back up to capacity using Enhanced Geothermal Systems (EGS) technology. The Geysers geothermal field is located two hours north of San Francisco, California, and therefore, the article drew comparisons to a similar geothermal EGS project in Basel, Switzerland believed to cause a magnitude 3.4 earthquake. In order to address public concern and gain acceptance from the general public and policymakers for geothermal energy development, specifically EGS, the U.S. Department of Energy commissioned a group of experts in induced seismicity, geothermal power development and risk assessment to write a revised Induced Seismicity Protocol. The authors met with the domestic and international scientific community, policymakers, and other stakeholders to gain their perspectives and incorporate them into the Protocol. They also incorporated the lessons learned from Basel, Switzerland and other EGS projects around the world to better understand the issues associated with induced seismicity in EGS projects. The Protocol concludes that with proper study and technology development induced seismicity will not only be mitigated, but will become a useful tool for reservoir management. This Protocol is a living guidance document for geothermal developers, public officials, regulators and the general public that provides a set of general guidelines detailing useful steps to evaluate and manage the effects of induced seismicity related to EGS projects. This Protocol puts high importance on safety while allowing geothermal technology to move forward in a cost effective manner. The goal of this Protocol is to help facilitate the successful deployment of EGS projects, thus increasing the availability of clean, renewable and domestic energy in the United States. Project developers should work closely with the National Environmental Policy Act (NEPA) compliance officials of the involved Federal agency(ies) to align information needs and public involvement activities with the NEPA review process. The authors emphasize this Protocol is neither a substitute nor a panacea for regulatory requirements that may be imposed by federal, state or local regulators. I would like to acknowledge everyone who gave their time and expertise at the induced seismicity workshops (see Appendix D) that led to this updated Protocol. Their input was critical to develop an informed and useful document. In addition, I would like to thank the authors of this document, whose ideas and support came together to write a clear and concise Protocol. This document was put out for public comment and reviewed by NEPA, the U.S. Department of Energy and General Counsel. Special thanks to Christy King-Gilmore and Brian Costner for their guidance.

Abstract. Near-surface investigations often require characterization of vadose zone hydraulic parameters. Conventional sampling or borehole techniques for estimating these parameters are costly, time consuming, and invasive, all of which limit collection of hydrogeological data at a spacing needed for detailed site characterization. Incorporation of two-or three-dimensional densely sampled geophysical data with conventional hydrological data increases the amount of data available for the characterization and thus has the potential to significantly improve the hydraulic parameter estimates over those obtained from borehole data alone. The hydraulic estimation procedure can be greatly improved by incorporating dielectric information potentially available from ground penetrating radar (GPR), a noninvasive, high-resolution geophysical method. The procedures for collecting and processing GPR data in the format needed for the proposed estimation technique are relatively new and still a topic of research; our method requires as a starting point the ability to estimate dielectric constants from GPR data. Numerical experiments were performed to investigate the general utility of the GPR-assisted estimation technique under a range of conditions. Three bimodal systems were investigated, each system being composed of a sand facies together with another facies with a larger clay volume fraction; each facies was defined using characteristic values of clay content, porosity, and permeability. Using dielectric information and petrophysical relations, degree of saturation and intrinsic permeability values at each location within the three systems were identified. For bimodal systems, a dielectric constant measurement corresponds to two possible values of saturation and intrinsic permeability at each location; single values of saturation and intrinsic permeability were estimated from these values using the principle of maximum likelihood. Results from case studies demonstrate that a combination of GPR data with conventional borehole data significantly improves the estimates of saturation and has the potential to improve the estimates of permeability over those obtained from well bore data alone. The proposed method should be especially advantageous for vadose zone characterization in areas favorable for GPR data acquisition, where detailed hydraulic parameter information is required but the drilling of numerous boreholes is prohibited. IntroductionNear-surface environmental, agricultural, and engineering investigations often require detailed characterization of vados½ zone hydraulic parameters. Estimates of hydraulic conductivity are needed to model and predict pollutant transport through the subsurface and to subsequently design an efficient and reliable rcmcdiation plan. Soil water content monitoring is important, for example, to maintain an optimal balance between crop yield and groundwater pumping [Toppet al., 1980 Geophysical data together with borehole information have been used in the petroleum industry for decades to aid ...

Abstract. The large spatial variability of hydraulic properties in natural geologic systems over a wide range of scales, and the difficulty of collecting representative and sufficient hydraulic property measurements using conventional sampling techniques, render estimation of spatial correlation parameters difficult. Further compounding the estimation problem is the observation that the integral scale estimate is a function of the measurement support scale. To mitigate these problems, we investigate the use of tomographic geophysical data in combination with hydrogeological data in the spatial correlation estimation procedure. Two synthetic case studies were investigated where the scale of the geophysical measurements were varied relative to the scale of the hydrogeological properties. The spatial correlation structure parameter estimation procedure was performed in the spectral domain, where analysis of data having different support scales and spatial sampling windows was facilitated. Comparison of the spatial correlation structure parameters estimated from measured data with those of the synthetic aquifers revealed which type of data (tomographic, hydrogeological, or a combination of both) was most effective for recovering spatial correlation statistics under different sampling/heterogeneity conditions. These synthetic case studies suggest that collection of a few tomographic profiles and interpretation of these profiles together with limited well bore data can yield correlation structure information that is otherwise obtainable only from extensive hydrological sampling. IntroductionNatural geologic systems exhibit large spatial variability of hydrogeologic properties such as hydraulic conductivity over a wide range of scales. Environmental, engineering, and agricultural studies often require information about the spatial correlation structure of these properties. For example, groundwater flow modeling is often performed through an aquifer whose hydrological properties have been created using stochastic simulation techniques; these techniques require as input information about the spatial correlation structure. Hydraulic conductivity measurements are obtained in the laboratory using permeameters or minipermeameters on core samples or in the field using downhole flowmeters, slug tests, and pumping tests. It can be difficult to estimate the spatial correlation structure of these properties using these conventional field sampling techniques because (1) well bore data are commonly scarce, especially in the horizontal direction, and (2) hydrological techniques require drilling, and the installed wells change the nature of the flow processes in the vicinity of the probes, which may yield hydraulic conductivity values which are not representative of unsampled and undisturbed areas. In addition to these problems, experimental and numerical studies have suggested that the hydraulic conductivity integral scales that are [Beckie, 1996]. To mitigate the problems associated with collecting well bore hydraulic conductivity...

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A 3-D surface seismic survey was condu geothermal reservoir (Nevada), to deter applied in geothermal environments: Furthermore, it was intended to map the structural features which may control geothermal production in the reservoir. The seismic survey covered an area of 3.03 square miles and was designed with 12 north-south receiver lines and 25 east-west source lines. The receiver group interval was 100 feet and the receiver line spacing was 800 feet. The source interval was 100 feet while the source line spacing was 400 feet. The sources were comprised of 4 vibrator trucks arranged in a box array. Seismic processing involved, among other steps, the picking of over 700,000 of the possible one million traces to determine first arrival travel times, normal moveout correction, 3-D stack, deconvolution, time migration, and depth conversion. The final data set rep Additionally, the travel times wer to support the findings of the surface seismic imaging. The results suggest the presence of at least one dominant fault responsible for the migration of fluids in the reservoir. F'urthermore, it is suggested that this feature might be part of a fault system that includes a graben structure. structure of the Rye Patch mic techniques could be successfully nts a 3-D cube of the subsurface .structure in the reservoir. ed to perform tomogwhic inversions for velocity estimates This preprint was prepared with AGU's IlylEx macros v4.

Earthquakes and other seismic sources produce waves with frequency content spanning many orders of magnitude. Recording a broader frequency band of interest has historically required deploying multiple instruments designed to work the best within limited, overlapping frequency ranges. Here, we detail a 300 m deep borehole deployment of a sensor package, including three new optical accelerometers that can potentially replace many dedicated instruments with a single, low-noise sensor. These instruments are designed with a flat frequency response from 0.005 to 1500 Hz, spanning the flat response segments of broadband sensors and geophones, as well as a low-noise floor and high sensitivity. The sensors have been functioning normally for over four years, fully grouted at depths of >100 m. Year-long power spectral density (PSD) profiles show that the optical accelerometers have a lower noise floor than a colocated geophone for all frequencies, with 20 dB noise reduction at 250 Hz. PSD comparisons to a broadband sensor installed at the surface show a 5–30 dB noise reduction for the optical accelerometer above 1 Hz, although this is likely due, in part, to the broadband sensor being subjected to much higher surface noise. At periods >5 s, the broadband sensor shows up to 20 dB lower noise than the optical accelerometer, which in turn has up to 50 dB lower noise floor than the colocated geophone. Finally, modeling the Brune displacement spectrum for theoretical seismicity within 1 km of the borehole shows that the optical accelerometers could potentially deliver a detection threshold improvement of one magnitude unit relative to the colocated geophone.

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