--> ABSTRACT: Temporary Diverters for EGS Reservoir Optimization, by Bour, Daniel; Cladouhos, Trenton ; Petty, Susan; Nordin, Yini ; #90142 (2012)

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Temporary Diverters for EGS Reservoir Optimization

Bour, Daniel 1; Cladouhos, Trenton *1; Petty, Susan 1; Nordin, Yini 1
(1) AltaRock Energy, Seattle, WA.

Engineered or Enhanced Geothermal Systems (EGS) have the potential to expand the availability of clean renewable, baseload energy beyond conventional geothermal areas. An EGS reservoir is created by injecting large volumes of cold water into hot, low-permeability rock to induce seismic slip and enhance the permeability of pre-existing fractures. Early EGS demonstrations have been limited to a single stimulation per well because a method to isolate the first fracture has been lacking.

Multiple zone stimulation in the open-hole sections of EGS wells would significantly reduce the cost of EGS power production by increasing the productivity of each well. Economic models indicate a reduction in the cost of EGS power of up to 50 percent if three fracture zones can be successfully stimulated per well, versus the current limit a single stimulated fracture zone per well. A successful field test of this concept was recently performed by AltaRock Energy Inc.
(AltaRock) in a producing geothermal field. The goal of the operation was to test AltaRock’s proprietary thermo-degradable zonal isolation materials (TZIM) to temporarily seal off fractures in a geothermal well, allowing for stimulation of secondary and tertiary fracture zones, thus optimizing the injection/production profile of the entire well.

TZIM blocks flow to zones that are already stimulated or where stimulation is not desired. After a stimulation treatment these proprietary diverter materials decay due to thermal degradation, producing environmentally benign decomposition products. Successful field results are presented along with a detailed explanation of the benefits of temporary diverters and how they could positively impact EGS projects and geothermal power production in general. These methods will be further validated at the upcoming Newberry Volcano EGS Demonstration, funded in part by DOE Grant DE-EE0002777. The diverter development work has been funded in part by DOE Grant DE-EE0002795.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California