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Title: Development of a Neutron Diffraction Based Experiemental Capability for Investigating Hydraulic Fracturing for EGS-like Conditions
Creator/Author: Polsky, Yarom [ORNL] ; Anovitz, Lawrence {Larry} M [ORNL] ; An, Ke [ORNL] ; Carmichael, Justin R [ORNL] ; Bingham, Philip R [ORNL] ; Dessieux Jr, Luc Lucius [ORNL]
Publication Date:2013 Jan 01
OSTI Identifier:OSTI 1061556
Report Number(s):None
DOE Contract Number:DE-AC05-00OR22725
Document Type:Conference
Specific Type:
Resource Relation:Conference: Stanford Geothermal Workshop, Palo Alto, CA, USA, 20130211, 20130213
Other Number(s):
Research Org:Oak Ridge National Laboratory (ORNL); Spallation Neutron Source
Sponsoring Org:EE USDOE - Office of Energy Efficiency and Renewable Energy (EE)
Keywords:egs; geothermal; hydraulic fracture; rock mechanics; stress; strain
Description/Abstract:Hydraulic fracturing to enhance formation permeability is an established practice in the Oil & Gas (O&G) industry and is expected to be an enabler for EGS. However, it is rarely employed in conventional geothermal systems and there are significant questions regarding the translation of practice from O&G to both conventional geothermal and EGS applications. Lithological differences(sedimentary versus crystalline rocks, significantly greater formation temperatures and different desired fracture characteristics are among a number of factors that are likely to result in a gap of understanding of how to manage hydraulic fracturing practice for geothermal. Whereas the O&G community has had both the capital and the opportunity to develop its understanding of hydraulic fracturing operations empirically in the field as well through extensive R&D efforts, field testing opportunities for EGS are likely to be minimal due to the high expense of hydraulic fracturing field trials. A significant portion of the knowledge needed to guide the management of geothermal/EGS hydraulic fracturing operations will therefore likely have to come from experimental efforts and simulation. This paper describes ongoing efforts at Oak Ridge National Laboratory (ORNL) to develop an experimental capability to map the internal stresses/strains in core samples subjected to triaxial stress states and temperatures representative of EGS-like conditions using neutron diffraction based strain mapping techniques. This capability is being developed at ORNL\'s Spallation Neutron Source, the world\'s most powerful pulsed neutron source and is still in a proof of concept phase. A specialized pressure cell has been developed that permits independent radial and axial fluid pressurization of core samples, with axial flow through capability and a temperature rating up to 300 degrees C. This cell will ultimately be used to hydraulically pressurize EGS-representative core samples to conditions of imminent fracture and map the associated internal strain states of the sample. This will hopefully enable a more precise mapping of the rock material failure envelope, facilitate a more refined understanding of the mechanism of hydraulically induced rock fracture, particularly in crystalline rocks, and serve as a platform for validating and improving fracture simulation codes. The elements of the research program and preliminary strain mapping results of a Sierra White granite sample subjected only to compressive loading will be discussed in this paper.
Country of Publication:US
Size/Format:Medium: X
System Entry Date:2014 Jun 24
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