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Title: Geothermal fracture stimulation technology. Volume II. High-temperature proppant testing

Abstract

Data were obtained from a newly built proppant tester, operated at actual geothermal temperatures. The short term test results show that most proppants are temperature sensitive, particularly at the higher closure stresses. Many materials have been tested using a standard short-term test, i.e., fracture-free sand, bauxite, and a resin-coated sand retained good permeability at the high fluid temperatures in brine over a range of closure stresses. The tests were designed to simulate normal closure stress ranges for geothermal wells which are estimated to be from 2000 to 6000 psi. Although the ultra high closure stresses in oil and gas wells need not be considered with present geothermal resources, there is a definite need for chemically inert proppants that will retain high permeability for long time periods in the high temperature formations.

Publication Date:
Research Org.:
Republic Geothermal, Inc., Santa Fe Springs, CA (USA)
OSTI Identifier:
6852571
Report Number(s):
DOE/AL/10563-T8(Vol.2)
DOE Contract Number:
AC32-79AL10563
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GEOTHERMAL WELLS; PROPPING AGENTS; PERFORMANCE TESTING; ALUMINIUM OXIDES; BAUXITE; CORUNDUM; DENSITY; HYDRAULIC FRACTURING; MECHANICAL PROPERTIES; PERMEABILITY; PHYSICAL PROPERTIES; SAND; STRESSES; WELL STIMULATION; ALUMINIUM COMPOUNDS; ALUMINIUM ORES; CHALCOGENIDES; COMMINUTION; FRACTURING; MINERALS; ORES; OXIDES; OXYGEN COMPOUNDS; STIMULATION; TESTING; WELLS Geothermal Legacy 150906* -- Geothermal Engineering-- Reservoir Stimulation & Extraction Technology

Citation Formats

Not Available. Geothermal fracture stimulation technology. Volume II. High-temperature proppant testing. United States: N. p., 1980. Web. doi:10.2172/6852571.
Not Available. Geothermal fracture stimulation technology. Volume II. High-temperature proppant testing. United States. doi:10.2172/6852571.
Not Available. 1980. "Geothermal fracture stimulation technology. Volume II. High-temperature proppant testing". United States. doi:10.2172/6852571. https://www.osti.gov/servlets/purl/6852571.
@article{osti_6852571,
title = {Geothermal fracture stimulation technology. Volume II. High-temperature proppant testing},
author = {Not Available},
abstractNote = {Data were obtained from a newly built proppant tester, operated at actual geothermal temperatures. The short term test results show that most proppants are temperature sensitive, particularly at the higher closure stresses. Many materials have been tested using a standard short-term test, i.e., fracture-free sand, bauxite, and a resin-coated sand retained good permeability at the high fluid temperatures in brine over a range of closure stresses. The tests were designed to simulate normal closure stress ranges for geothermal wells which are estimated to be from 2000 to 6000 psi. Although the ultra high closure stresses in oil and gas wells need not be considered with present geothermal resources, there is a definite need for chemically inert proppants that will retain high permeability for long time periods in the high temperature formations.},
doi = {10.2172/6852571},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1980,
month = 7
}

Technical Report:

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  • Crushing and degradation mechanisms of proppants are examined to characterize proppants and assess their usability in geothermal wells. Short-term tests can tell the physical strength of a proppant, but long-term tests are required to ascertain any interrelated chemical effects. Degradation of proppants is measured as a loss in permeability and can be correlated to temperature, time, and closure stress. Sand is a common proppant which is strongly affected by higher temperature and closure stress. Even at low stress levels, sand degrades in brine or hot water with long-term exposure. Most geothermal waters and their pH levels can also be detrimentalmore » to sand. There are some proppants with desirable properties at geothermal conditions. These are resistant to the crushing loads or closure stress in geothermal wells and will not react or dissolve in high temperature brines. While there are limits to these proppants, an unqualified list of possible geothermal proppants is given: aluminum oxide, garnet, resin-coated proppants, and sintered bauxite.« less
  • A detailed study of all available and experimental frac fluid systems is presented. They have been examined and tested for physical properties that are important in the stimulation of hot water geothermal wells. These fluids consist of water-based systems containing high molecular weight polymers in the uncrosslinked and crosslinked state. The results of fluid testing for many systems are summarized specifically at geothermal conditions or until breakdown occurs. Some of the standard tests are ambient viscosity, static aging, high temperature viscosity, fluid-loss testing, and falling ball viscosity at elevated temperatures and pressures. Results of these tests show that unalterable breakdownmore » of the polymer solutions begins above 300/sup 0/F. This continues at higher temperatures with time even if stabilizers or other high temperature additives are included.« less
  • A review of previously published literature on proppant permeability is presented. This data will be used in the subsequent phases of the geothermal stimulation project. Much information comes from the oil and gas industry which has tested various proppants during the past thirty years over a range of different closure stresses at the lower temperatures found in oil reservoirs. The historical development of proppants is summarized and reviewed and a variety of data on proppants found in today's literature is presented. Also included are several standard test procedures and equipment setups used in measuring proppant properties and in proppant testing.
  • Conventional drill bit steels exhibit increased wear and decreased toughness when run at elevated temperatures in geothermal wells. Bits are therefore run at lower speeds and lighter loads, resulting in lower penetration rates for geothermal drilling than for conventional rock drilling. Carpenter EX-00053, Timken CBS 600, Timken CBS 1000M and Vasco X-2M steels with improved hot hardness (improved wear resistance), were tested in conjunction with the steels used for cones (AISI 4829, 3915 and EX55) in conventional roller cones and lugs (AISI 8620, 9315 and EX55) in conventional roller cone rock bits. Short-rod fracture toughness measurements were made on eachmore » of these steels between room temperature and 400{degree}C. Fatigue crack resistance was determined at 300{degree}C for high-temperature steels and at room temperature for conventional steels. Scanning electron microscopy analyses of the fractured short-rod specimens were correlated with observed crack behavior from the test records. Materials testing results are discussed and steel selections made for improved geothermal bits. Carpenter EX-00053 and Timken CBS 1000M steels meet all design requirements for use in stabilizers, lugs and cones at temperatures to 400{degree}C. It is recommended that EX-00053 and CBS 1000M be manufactured for geothermal drilling at the Geysers site. [DJE 2005]« less
  • Conventional drill bit steels exhibit increased wear and decreased toughness when run at elevated temperatures in geothermal wells. Bits are therefore run at lower speeds and lighter loads, resulting in lower penetration rates for geothermal wells than for conventional rock drilling. Carpenter EX-00053, Timken CBS 600, Timken CBS 1000M and Vasco X-2M, steels with improved hot hardness (improved wear resistance), were tested in conjunction with the steels used for cones (AISI 4820 and 9315) and lugs (AISI 8620 and 9315) in conventional roller cone rock bits. Shortrod fracture toughness measurements were made on each of these steels between room temperaturemore » and 400/sup 0/C. Fatigue crack resistance was determined at 300/sup 0/C for high-temperature steels and at room temperature for conventional steels. Scanning electron microscopy analyses of the fractured short-rod specimens were correlated with observed crack behavior from the test records. Test results are discussed, recommendations made for further testing and preliminary steel selections made for improved geothermal bits.« less