TY - JOUR
T1 - Environmentally friendly, rheoreversible, hydraulic-fracturing fluids for enhanced geothermal systems
AU - Shao, Hongbo
AU - Kabilan, Senthil
AU - Stephens, Sean
AU - Suresh, Niraj
AU - Beck, Anthon N.
AU - Varga, Tamas
AU - Martin, Paul F.
AU - Kuprat, Andrew
AU - Jung, Hun Bok
AU - Um, Wooyong
AU - Bonneville, Alain
AU - Heldebrant, David J.
AU - Carroll, Kenneth C.
AU - Moore, Joseph
AU - Fernandez, Carlos A.
N1 - Funding Information:
Funding for this research was provided by the Geothermal Technology Office of the U.S. Department of Energy . XMT analysis was performed in EMSL (Environmental Molecular Sciences Laboratory; EMSL proposal # 47743), a DOE national scientific user facility at Pacific Northwest National Laboratory (PNNL). Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC06-76RLO 1830.
Publisher Copyright:
© 2015 Elsevier Ltd.
PY - 2015/11/1
Y1 - 2015/11/1
N2 - Cost-effective creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the feasibility of enhanced geothermal systems (EGS). Current reservoir stimulation entails adverse environmental impacts and substantial economic costs due to the utilization of large volumes of water "doped" with chemicals including rheology modifiers, scale and corrosion inhibitors, biocides, friction reducers among others where, typically, little or no information of composition and toxicity is disclosed. An environmentally benign, CO2-activated, rheoreversible fracturing fluid has recently been developed that significantly enhances rock permeability at effective stress considerably lower than current technology based on laboratory-scale tests. In the present work we evaluate the potential of this novel fracturing fluid for application at geothermal sites under different chemical and geomechanical conditions, by performing laboratory-scale fracturing experiments with different rock sources under different confining pressures, temperatures, and pH environments. The results demonstrate that CO2-reactive aqueous solutions of environmentally amenable polyallylamine (PAA) represent a highly versatile fracturing fluid technology. This fracturing fluid consistently and reproducibly creates/propagates fracture networks through highly impermeable crystalline rock from Coso EGS and Newberry EGS sites at significantly lower effective stress as compared to conventional fracturing fluids. In addition, permeability was significantly enhanced (several orders of magnitude). This was evident in all laboratory-scale experiments, including variable rock source/type, operation pressure and temperature (over the entire range for EGS applications), as well as over a wide range of formation-water pH values. This effective, versatile, and environmentally-friendly fracturing fluid technology represents a significant advancement compared to industrially available fracturing fluids for cost-effective and competitive geothermal energy production.
AB - Cost-effective creation of high-permeability reservoirs inside deep crystalline bedrock is the primary challenge for the feasibility of enhanced geothermal systems (EGS). Current reservoir stimulation entails adverse environmental impacts and substantial economic costs due to the utilization of large volumes of water "doped" with chemicals including rheology modifiers, scale and corrosion inhibitors, biocides, friction reducers among others where, typically, little or no information of composition and toxicity is disclosed. An environmentally benign, CO2-activated, rheoreversible fracturing fluid has recently been developed that significantly enhances rock permeability at effective stress considerably lower than current technology based on laboratory-scale tests. In the present work we evaluate the potential of this novel fracturing fluid for application at geothermal sites under different chemical and geomechanical conditions, by performing laboratory-scale fracturing experiments with different rock sources under different confining pressures, temperatures, and pH environments. The results demonstrate that CO2-reactive aqueous solutions of environmentally amenable polyallylamine (PAA) represent a highly versatile fracturing fluid technology. This fracturing fluid consistently and reproducibly creates/propagates fracture networks through highly impermeable crystalline rock from Coso EGS and Newberry EGS sites at significantly lower effective stress as compared to conventional fracturing fluids. In addition, permeability was significantly enhanced (several orders of magnitude). This was evident in all laboratory-scale experiments, including variable rock source/type, operation pressure and temperature (over the entire range for EGS applications), as well as over a wide range of formation-water pH values. This effective, versatile, and environmentally-friendly fracturing fluid technology represents a significant advancement compared to industrially available fracturing fluids for cost-effective and competitive geothermal energy production.
KW - Enhanced geothermal systems
KW - Environmentally-friendly
KW - Expansion
KW - Fracturing fluid
KW - Rheoreversible
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U2 - 10.1016/j.geothermics.2015.07.010
DO - 10.1016/j.geothermics.2015.07.010
M3 - Article
AN - SCOPUS:84941561634
SN - 0375-6505
VL - 58
SP - 22
EP - 31
JO - Geothermics
JF - Geothermics
ER -