Geothermal reservoir characterization using distributed temperature sensing at Brady Geothermal Field, Nevada

Abstract

Distributed temperature sensing (DTS) systems provide near real-time data collection that captures borehole spatiotemporal temperature dynamics. Temperature data were collected in an observation well at an active geothermal site for a period of eight days under geothermal production conditions. Collected temperature data showcase the ability of DTS systems to detect changes to the location of the steam-water interface, visualize borehole temperature recovery-following injection of a cold-water "slug"-and identify anomalously warm and/or cool zones. The high sampling rate and spatial resolution of DTS data also shows borehole temperature dynamics that are not captured by traditional pressure-temperature survey tools. Inversion of thermal recovery data using a finitedifference heat-transfer model produces a thermal-diffusivity profile that is consistent with laboratory-measured values and correlates with identified lithologic changes within the borehole. Used alone or in conjunction with complementary data sets, DTS systems are useful tools for developing a better understanding of both reservoir rock thermal properties as well as within and near borehole fluid movement. The work presented herein has been funded in part by the Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy, under Award Number DE-EE0006760.

Geodetic Measurements and Numerical Models of Deformation at Coso Geothermal Field, California, USA, 2004–2016

“…where τ is a characteristic time scale found through nonlinear optimization. This trend would be consistent with drawdown as has been observed at Brady (e.g., [43,44]).…”

Geothermal reservoir characterization using distributed temperature sensing at Brady Geothermal Field, Nevada

“…This research was supported by grants DE-EE0005510 and DE-EE0006760 from the U.S. Department of Energy Geothermal Technologies Office. The data used are listed in the references in the "The Leading Edge" article by Patterson et al, 2017, and can be found on the Geothermal Data Repository at https://gdr.openei.org/submissions/853.…”

Time‐Series Analysis of Volume Change at Brady Hot Springs, Nevada, USA, Using Geodetic Data From 2003–2018

“…Thus, we reject the null hypothesis at 95% confidence and conclude that the volume change rate of the deforming region is inversely related to the (net) injection rate at the site. Furthermore, the cessation of both production and injection pumping during Stage 2 led to fluid pressure changes as large as 150 kPa (roughly equivalent to 15 m of water) (Patterson et al, 2017).…”

“…The parameterized model is comprised of a single grid layer of 1,656 cubic voxels each with a volume of (100 m) 3 centered at a (previously optimized) depth of 100 m, consistent with the depth of the phreatic surface at Brady (Patterson et al, 2017). Here, we use the term “phreatic surface” instead of “water table” because the observations at Brady suggest that a continuous, horizontal water table is not present (Patterson, 2018; Patterson et al, 2017). The geometrical complexity of this model helps clarify the spatial distribution of deformation.…”

“…We then apply the “multicube” parameterization introduced by Reinisch et al (2018) which describes the observed rates of subsidence in terms of the volume change rate of the reservoir. The parameterized model is comprised of a single grid layer of 1,656 cubic voxels each with a volume of (100 m) 3 centered at a (previously optimized) depth of 100 m, consistent with the depth of the phreatic surface at Brady (Patterson et al, 2017). Here, we use the term “phreatic surface” instead of “water table” because the observations at Brady suggest that a continuous, horizontal water table is not present (Patterson, 2018; Patterson et al, 2017).…”