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Title: Characterization of injection wells in a fractured reservoir using PTS logs, Steamboat Hills Geothermal Field, Nevada, USA

Abstract

The Steamboat Hills Geothermal Field in northwestern Nevada, about 15 km south of Reno, is a shallow (150m to 825m) moderate temperature (155 C to 168 C) liquid-dominated geothermal reservoir situated in highly-fractured granodiorite. Three injection wells were drilled and completed in granodiorite to dispose of spent geothermal fluids from the Steamboat II and III power plants (a 30 MW air-cooled binary-type facility). Injection wells were targeted to depths below 300m to inject spent fluids below producing fractures. First, quasi-static downhole pressure-temperature-spinner (PTS) logs were obtained. Then, the three wells were injection-tested using fluids between 80 C and 106 C at rates from 70 kg/s to 200 kg/s. PTS logs were run both up and down the wells during these injection tests. These PTS surveys have delineated the subsurface fracture zones which will accept fluid. The relative injectivity of the wells was also established. Shut-in interzonal flow within the wells was identified and characterized.

Authors:
;
Publication Date:
Research Org.:
Geological Engineering consultant, Richmond, CA; Geo Hills Associated, Los Altos Hill, CA
Sponsoring Org.:
USDOE
OSTI Identifier:
889352
Report Number(s):
SGP-TR-150-8
TRN: US200619%%787
Resource Type:
Conference
Resource Relation:
Conference: Proceedings, Twentieth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 24-26, 1995
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; 02 PETROLEUM; FRACTURED RESERVOIRS; FRACTURES; GEOTHERMAL FIELDS; GEOTHERMAL FLUIDS; GRANODIORITES; INJECTION WELLS; NEVADA; POWER PLANTS; RESERVOIR ENGINEERING; USA; Geothermal Legacy

Citation Formats

Goranson, Colin, and Combs, Jim. Characterization of injection wells in a fractured reservoir using PTS logs, Steamboat Hills Geothermal Field, Nevada, USA. United States: N. p., 1995. Web.
Goranson, Colin, & Combs, Jim. Characterization of injection wells in a fractured reservoir using PTS logs, Steamboat Hills Geothermal Field, Nevada, USA. United States.
Goranson, Colin, and Combs, Jim. Thu . "Characterization of injection wells in a fractured reservoir using PTS logs, Steamboat Hills Geothermal Field, Nevada, USA". United States. doi:. https://www.osti.gov/servlets/purl/889352.
@article{osti_889352,
title = {Characterization of injection wells in a fractured reservoir using PTS logs, Steamboat Hills Geothermal Field, Nevada, USA},
author = {Goranson, Colin and Combs, Jim},
abstractNote = {The Steamboat Hills Geothermal Field in northwestern Nevada, about 15 km south of Reno, is a shallow (150m to 825m) moderate temperature (155 C to 168 C) liquid-dominated geothermal reservoir situated in highly-fractured granodiorite. Three injection wells were drilled and completed in granodiorite to dispose of spent geothermal fluids from the Steamboat II and III power plants (a 30 MW air-cooled binary-type facility). Injection wells were targeted to depths below 300m to inject spent fluids below producing fractures. First, quasi-static downhole pressure-temperature-spinner (PTS) logs were obtained. Then, the three wells were injection-tested using fluids between 80 C and 106 C at rates from 70 kg/s to 200 kg/s. PTS logs were run both up and down the wells during these injection tests. These PTS surveys have delineated the subsurface fracture zones which will accept fluid. The relative injectivity of the wells was also established. Shut-in interzonal flow within the wells was identified and characterized.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 26 00:00:00 EST 1995},
month = {Thu Jan 26 00:00:00 EST 1995}
}

Conference:
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  • Three slim holes were drilled at the Steamboat Hills Geothermal Field in northwestern Nevada about 15 km south of Reno. The slim holes were drilled to investigate the geologic conditions, thermal regime and productive characteristics of the geothermal system. They were completed through a geologic sequence consisting of alluvium cemented by geothermal fluids, volcaniclastic materials, and granodiorite. Numerous fractures, mostly sealed, were encountered throughout the drilled depth; however, several open fractures in the granodiorite, dipping between 65 and 90{degree}, had apertures up to 13 mm in width. The depths of the slim holes vary from 262 to 277 m withmore » open-hole diameters of 76 mm. Pressure and temperature logs gave bottom-hole temperatures ranging from 163 to 166{degree} C. During injection testing, downhole pressures were measured using capillary tubing with a surface quartz transducer while temperatures were measured with a Kuster temperature tool located below the capillary tubing pressure chamber. No pressure increase was measured at reservoir depths in any of the three slim holes while injecting 11 kg/s of 29{degree}C water indicating a very high permeability in the geothermal reservoir. These injection test results suggested that productive geothermal fluids could be found at depths sufficient for well pumping equipment and at temperatures needed for electrical power production using binary-type conversion technology.« less
  • Geothermal fluids from the Steamboat Hills are silica-rich, Na-Cl waters. Maximum temperatures in the geothermal system are at least 230{degrees} to 235{degrees}C based on sulfate-water isotope and enthalpy-chloride relations and possibly as high as 243{degrees}C based on Na-K and gas geothermometry. The hottest geothermal well in the system (23-5) may have excess enthalpy. Chloride concentrations in the deep thermal fluid are {>=}706 ppm. Geothermal fluids are currently produced from both a high-temperature and a moderate-temperature well field. The high-temperature fluids are related to one another and to the moderate-temperature fluids principally by boiling. As the high-temperature fluids boil and coolmore » to moderate temperatures, silica precipitates from solution, calcium and magnesium concentrations increase, and K/Na values partially adjust to the lower temperatures. Full chemical equilibrium may occur only in the high-temperature waters. In the new part of the moderate-temperature field (wells PW2-1 to PW3-4), K/Na values were initially very similar, but utilization has caused some wells to change composition. However, the general trend over time is to lower silica and K/Na values in all moderate-temperature wells. This trend probably indicates that heat is being {open_quotes}mined{close_quotes} from the aquifer-rock. Mixing of cold, low-chloride ground water with thermal water is important only near the toe of the system in the sediments which fill the valley. Steam-heated ground waters occur in the sediments along the north side of the Steamboat Hills.« less
  • This study, in the Steamboat Hills area of the Carson segment of the northern Walker Lane Belt, was initiated to provide a regional thermal history framework and to investigate the age of the active local hydrothermal system. Seven outcrop samples, representing ?Cretaceous granodiorite and ?Triassic Peavine sequence metamorphosed volcanic flow and volcaniclastic rocks plus six samples of Peavine rocks in vertical sequence from an 0.8 km deep geothermal corehole have been analyzed using AFTA (apatite fission track analysis) and zircon fission track analysis.
  • Distributed temperature sensing (DTS) systems provide near real-time data collection that captures borehole spatiotemporal temperature dynamics. For this study, temperature data was 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 coldwater “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 bymore » traditional pressure-temperature survey tools. Inversion of thermal recovery data using a finite-difference heat-transfer model produces a thermal-diffusivity profile that is consistent with laboratorymeasured 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.« less