The Northwest Geysers EGS Demonstration Project, California

García, Julio; Hartline, Craig; Walters, Mark; Wright, Melinda; Rutqvist, Jonny; Dobson, Patrick; Jeanne, Pierre

doi:10.1016/j.geothermics.2015.08.003

Cited by 99 publications

(60 citation statements)

References 13 publications

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“…A steam entry was encountered in the deepened Prati-32 well at 3352 m with a measured temperature of 400 °C. Drilling difficulties caused by elevated temperatures (the well was drilled with air) led to low rates of penetration (ROP, 3 m/h) and extreme bit wear (the last roller cone bit only lasted 30 m); thus the well was completed at a depth of 3396 m. This well was used as the injection well for the EGS production-injection well pair for this project (Garcia et al 2016).…”

Section: Drilling Of Supercritical Systems In the Usmentioning

confidence: 99%

Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities

Reinsch

Dobson

Asanuma³

et al. 2017

Geotherm Energy

158

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Section: Drilling Of Supercritical Systems In the Usmentioning

confidence: 99%

Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities

Reinsch

Dobson

Asanuma³

et al. 2017

Geotherm Energy

158

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“…1. NE-SW geologic cross-section through the northwest Geysers including the two wells P-32 and PS-31 that were reopened and recompleted as an injection/production pair within the HTR (Garcia et al, 2012). geothermal systems (EGS) could be created and successfully managed at existing high-temperature geothermal systems, then large untapped resources could be made available for energy production.…”

Section: Introductionmentioning

confidence: 99%

The Northwest Geysers EGS Demonstration Project, California – Part 2: Modeling and interpretation

et al. 2016

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a b s t r a c tIn this paper, we summarize the results of coupled thermal, hydraulic, and mechanical (THM) modeling in support of the Northwest Geysers EGS Demonstration Project, which aims at enhancing production from a known High Temperature Reservoir (HTR) (280-400 • C) located under the conventional (240 • C) geothermal steam reservoir. The THM modeling was conducted to investigate geomechanical effects of cold-water injection during the stimulation of the EGS, first to predict the extent of the stimulation zone for a given injection schedule, and then to conduct interpretive analyses of the actual stimulation. By using a calibrated THM model based on historic injection and microseismic data at a nearby well, we could reasonably predict the extent of the stimulation zone around the injection well, at least for the first few months of injection. However, observed microseismic evolution and pressure responses over the one-year stimulation-injection revealed more heterogeneous behavior as a result of more complex geology, including a network of shear zones. Therefore, for an interpretive analysis of the one-year stimulation campaign, we included two sets of vertical shear zones within the model; a set of more permeable NWstriking shear zones and a set of less permeable NE-striking shear zones. Our modeling indicates that the microseismic events in this system are related to shear reactivation of pre-existing fractures, triggered by the combined effects of injection-induced cooling around the injection well and rapid (but small) changes in steam pressure as far as a kilometer from the injection well. Overall, the integrated monitoring and modeling of microseismicity, ground surface deformations, reservoir pressure, fluid chemical composition, and seismic tomography depict an EGS system hydraulically bounded by some of the NE-striking low permeability shear zones, with the more permeable NW-striking shear zone providing liquid flow paths for stimulation deep (several kilometers) down into the HTR. The modeling indicates that a significant mechanical degradation (damage) inferred from seismic tomography, and potential changes in fracture porosity inferred from cross-well pressure responses, are related to shear rupture in the stimulation zone driven by both pressure and cooling effects.

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“…Calò et al (2011) used microseismicity generated during the stimulation of the 5 km deep EGS reservoir at Soultz-sous-forêt to perform timelapse P-wave tomography to infer pore pressure migration during injection. Various authors also explored the vast induced seismicity dataset of > 500 000 events recorded since the 1960s at the Geysers geothermal site, where recently also an EGS demonstration stimulation has been performed (Garcia et al, 2012;Jeanne et al, 2014). The observed seismicity was partly related to injections (Jeanne et al, 2015) and thermoelastic stress changes (Rutqvist and Oldenburg, 2008).…”

Section: Induced Seismicitymentioning

confidence: 99%

The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

et al. 2018

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Abstract. In this contribution, we present a review of scientific research results that address seismo-hydromechanically coupled processes relevant for the development of a sustainable heat exchanger in low-permeability crystalline rock and introduce the design of the In situ Stimulation and Circulation (ISC) experiment at the Grimsel Test Site dedicated to studying such processes under controlled conditions. The review shows that research on reservoir stimulation for deep geothermal energy exploitation has been largely based on laboratory observations, large-scale projects and numerical models. Observations of full-scale reservoir stimulations have yielded important results. However, the limited access to the reservoir and limitations in the control on the experimental conditions during deep reservoir stimulations is insufficient to resolve the details of the hydromechanical processes that would enhance process understanding in a way that aids future stimulation design. Small-scale laboratory experiments provide fundamental insights into various processes relevant for enhanced geothermal energy, but suffer from (1) difficulties and uncertainties in upscaling the results to the field scale and (2) relatively homogeneous material and stress conditions that lead to an oversimplistic fracture flow and/or hydraulic fracture propagation behavior that is not representative of a heterogeneous reservoir. Thus, there is a need for intermediate-scale hydraulic stimulation experiments with high experimental control that bridge the various scales and for which access to the target rock mass with a comprehensive monitoring system is possible. The ISC experiment is designed to address open research questions in a naturally fractured and faulted crystalline rock mass at the Grimsel Test Site (Switzerland). Two hydraulic injection phases were executed to enhance the permeability of the rock mass. During the injection phases the rock mass deformation across fractures and within intact rock, the pore pressure distribution and propagation, and the microseismic response were monitored at a high spatial and temporal resolution.

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The Northwest Geysers EGS Demonstration Project, California

Cited by 99 publications

References 13 publications

Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities

Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities

The Northwest Geysers EGS Demonstration Project, California – Part 2: Modeling and interpretation

The seismo-hydromechanical behavior during deep geothermal reservoir stimulations: open questions tackled in a decameter-scale in situ stimulation experiment

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