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Title: A study of electrical generating capacities of self-discharging slim holes

Abstract

Theoretical calculations have been performed to estimate the electrical generating capacities of small-diameter geothermal wells for off-grid rural electrification using wellhead generators. In these applications, generating capacities of interest are typically in the range 100-1000 kWe. The approach amounted to (1) calculating the “wellhead discharge characteristics” (water/steam discharge rates as functions of wellhead pressure) for a variety of hypothetical well and reservoir descriptions, (2) employing a mathematical representation for the net generating capacity of a wellhead powerplant as a function of its operating inlet pressure and steam inlet rate, and (3) varying the wellhead (= turbine inlet) pressure to identify the “optimum” pressure value at which the net electrical power is maximized. Calculations were carried out for well diameters from 75 mm to 300 mm, for well depths from 300 to 1200 meters, for reservoir temperatures from 100°C to 240°C, for piezometric surface depths (related to shut-in reservoir pressure) from zero to 250 meters, and for downhole productivity indices from 2 kg/s/bar to infinity. A few cases were also included in which the CO2 content of the reservoir fluid was non-zero (up to 1% by mass in the brine). Both backpressure and condensing single-flash steam turbine powerplants were considered. Themore » study was restricted to vertical wells of uniform inside diameter and to all-liquid in-situ reservoir fluids. Over fifteen thousand combinations of the above parameters were examined. The results indicate that slim holes as small as 100 mm inside diameter penetrating reservoirs with temperatures as low as 150°C can produce useful amounts of electrical power using condensing wellhead turbines (> 100 kWe). For higher reservoir temperatures, the electrical capacity of such a well can exceed one megawatt.« less

Authors:
Publication Date:
Research Org.:
S-Cubed, La Jolla, CA
Sponsoring Org.:
USDOE
OSTI Identifier:
889711
Report Number(s):
SGP-TR-151-9
Resource Type:
Conference
Resource Relation:
Conference: Proceedings, Twenty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 22-24, 1996 000889651 000889652 000889653 000889654 Proceedings, Twenty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 22-24, 1996 000889651 000889652 000889653 000889654 Proceedings, Twenty-First Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA, January 22-24, 1996
Country of Publication:
United States
Language:
English
Subject:
Geothermal Legacy

Citation Formats

Pritchett, J W. A study of electrical generating capacities of self-discharging slim holes. United States: N. p., 1996. Web.
Pritchett, J W. A study of electrical generating capacities of self-discharging slim holes. United States.
Pritchett, J W. 1996. "A study of electrical generating capacities of self-discharging slim holes". United States. https://www.osti.gov/servlets/purl/889711.
@article{osti_889711,
title = {A study of electrical generating capacities of self-discharging slim holes},
author = {Pritchett, J W},
abstractNote = {Theoretical calculations have been performed to estimate the electrical generating capacities of small-diameter geothermal wells for off-grid rural electrification using wellhead generators. In these applications, generating capacities of interest are typically in the range 100-1000 kWe. The approach amounted to (1) calculating the “wellhead discharge characteristics” (water/steam discharge rates as functions of wellhead pressure) for a variety of hypothetical well and reservoir descriptions, (2) employing a mathematical representation for the net generating capacity of a wellhead powerplant as a function of its operating inlet pressure and steam inlet rate, and (3) varying the wellhead (= turbine inlet) pressure to identify the “optimum” pressure value at which the net electrical power is maximized. Calculations were carried out for well diameters from 75 mm to 300 mm, for well depths from 300 to 1200 meters, for reservoir temperatures from 100°C to 240°C, for piezometric surface depths (related to shut-in reservoir pressure) from zero to 250 meters, and for downhole productivity indices from 2 kg/s/bar to infinity. A few cases were also included in which the CO2 content of the reservoir fluid was non-zero (up to 1% by mass in the brine). Both backpressure and condensing single-flash steam turbine powerplants were considered. The study was restricted to vertical wells of uniform inside diameter and to all-liquid in-situ reservoir fluids. Over fifteen thousand combinations of the above parameters were examined. The results indicate that slim holes as small as 100 mm inside diameter penetrating reservoirs with temperatures as low as 150°C can produce useful amounts of electrical power using condensing wellhead turbines (> 100 kWe). For higher reservoir temperatures, the electrical capacity of such a well can exceed one megawatt.},
doi = {},
url = {https://www.osti.gov/biblio/889711}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1996},
month = {1}
}

Conference:
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