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Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems

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This is a final technical report for the project: Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems (EGS). The goal is to demonstrate the feasibility of foam fracturing in EGS applications. The project, led by Oak Ridge National Laboratory (ORNL), was conducted in collaboration with Temple University. The report describes the research activities with Task 1 at ORNL: foam fracturing testing system development and experimental study on foam fracturing, and Task 2 at Temple University: foam testing and foam characterization.

Main findings are:
1. A foam fracturing test system has been developed at ORNL, which can be used to perform foam fracturing under pressure up to 6,000 psi. The system monitors foam density during fracturing online and is capable of testing materials in both monotonic and cyclic (up to 50 Hz) injections.
2. Foam fracturing tests were carried out on Charcoal black granite specimens with a blind borehole to the middle length. Two diameters of blind borehole were tested; G2 series: 9.53 mm and G3 series: 4.76 mm. N2-in-water foam was used with AOS as a surfactant.
3. There was a hole-size effect on fracture initiation pressure. The effect is smaller in the case of foam, which was influenced by the high penetrability of gas in foam. Breakdown pressure showed a behavior just as that of fracture pressure; namely an increased value for small hole samples, while the effect in water fracture was more impressive than in foam fracture.
4. Water mass was reduced in foam fracturing within similar range of breakdown pressures. In G2 series, it was decreased from 10.44 g for water fracturing to 5.17 g, representing more than 50% water reduction. Therefore, there is the potential to reduce water use in EGS stimulation through foam fracturing.
5. Use of cyclic injection has the potential to reduce the breakdown pressure and seismicity in EGS application. Experiments using 4-s cycle period found that specimens can be fractured with a low number of cycles. The fatigue pressure was approximately 64 - 77% of monotonic breakdown pressure for water fracturing and 58 - 94% of the breakdown pressure for foam fracturing.
6. A foam stability testing system has been developed that can test foam at 220 Deg C to 2,000 psi. Tested components of candidate foams included two gases: N2 and CO2; 4 surfactants: AOS, SDS, NP-40 and CTAC; 5 stabilizing agents: guar, bentonite clay, borate salt, silica NPs, and GO.
7. N2 and AOS provided the most stable performance over the tested ranges. Furthermore, the AOS foam with stabilizing agents of guar and borate salt (crosslinker) offered the highest half-life of 20 minutes at 200 Deg C and 1,000 psi.
8. Arrhenius equation and modified power law have been demonstrated to fit well the half-time vs. temperature and pressure data, respectively. These relations can be useful to provide the suggestion for future foam stability study.

This submission contains the supporting data developed during the project:
1) A final technical report
2) Granite fracturing data in monotonic and cyclic injections with water and N2 foam

Foam performance data in various temperatures and pressures, including half-time, is submitted separately.

Citation Formats

Oak Ridge National Laboratory. (2022). Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems [data set]. Retrieved from https://dx.doi.org/10.15121/1869256.
Export Citation to RIS
Wang, Hong, Wang, Jy-An, Polsky, Yarom, Ren, Fei, and Thakore, Viren. Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems. United States: N.p., 17 May, 2022. Web. doi: 10.15121/1869256.
Wang, Hong, Wang, Jy-An, Polsky, Yarom, Ren, Fei, & Thakore, Viren. Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems. United States. https://dx.doi.org/10.15121/1869256
Wang, Hong, Wang, Jy-An, Polsky, Yarom, Ren, Fei, and Thakore, Viren. 2022. "Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems". United States. https://dx.doi.org/10.15121/1869256. https://gdr.openei.org/submissions/1378.
@div{oedi_5709, title = {Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems}, author = {Wang, Hong, Wang, Jy-An, Polsky, Yarom, Ren, Fei, and Thakore, Viren.}, abstractNote = {This is a final technical report for the project: Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems (EGS). The goal is to demonstrate the feasibility of foam fracturing in EGS applications. The project, led by Oak Ridge National Laboratory (ORNL), was conducted in collaboration with Temple University. The report describes the research activities with Task 1 at ORNL: foam fracturing testing system development and experimental study on foam fracturing, and Task 2 at Temple University: foam testing and foam characterization.

Main findings are:
1. A foam fracturing test system has been developed at ORNL, which can be used to perform foam fracturing under pressure up to 6,000 psi. The system monitors foam density during fracturing online and is capable of testing materials in both monotonic and cyclic (up to 50 Hz) injections.
2. Foam fracturing tests were carried out on Charcoal black granite specimens with a blind borehole to the middle length. Two diameters of blind borehole were tested; G2 series: 9.53 mm and G3 series: 4.76 mm. N2-in-water foam was used with AOS as a surfactant.
3. There was a hole-size effect on fracture initiation pressure. The effect is smaller in the case of foam, which was influenced by the high penetrability of gas in foam. Breakdown pressure showed a behavior just as that of fracture pressure; namely an increased value for small hole samples, while the effect in water fracture was more impressive than in foam fracture.
4. Water mass was reduced in foam fracturing within similar range of breakdown pressures. In G2 series, it was decreased from 10.44 g for water fracturing to 5.17 g, representing more than 50% water reduction. Therefore, there is the potential to reduce water use in EGS stimulation through foam fracturing.
5. Use of cyclic injection has the potential to reduce the breakdown pressure and seismicity in EGS application. Experiments using 4-s cycle period found that specimens can be fractured with a low number of cycles. The fatigue pressure was approximately 64 - 77% of monotonic breakdown pressure for water fracturing and 58 - 94% of the breakdown pressure for foam fracturing.
6. A foam stability testing system has been developed that can test foam at 220 Deg C to 2,000 psi. Tested components of candidate foams included two gases: N2 and CO2; 4 surfactants: AOS, SDS, NP-40 and CTAC; 5 stabilizing agents: guar, bentonite clay, borate salt, silica NPs, and GO.
7. N2 and AOS provided the most stable performance over the tested ranges. Furthermore, the AOS foam with stabilizing agents of guar and borate salt (crosslinker) offered the highest half-life of 20 minutes at 200 Deg C and 1,000 psi.
8. Arrhenius equation and modified power law have been demonstrated to fit well the half-time vs. temperature and pressure data, respectively. These relations can be useful to provide the suggestion for future foam stability study.

This submission contains the supporting data developed during the project:
1) A final technical report
2) Granite fracturing data in monotonic and cyclic injections with water and N2 foam

Foam performance data in various temperatures and pressures, including half-time, is submitted separately.
}, doi = {10.15121/1869256}, url = {https://gdr.openei.org/submissions/1378}, journal = {}, number = , volume = , place = {United States}, year = {2022}, month = {05}}
https://dx.doi.org/10.15121/1869256

Details

Data from May 17, 2022

Last updated May 23, 2022

Submitted May 19, 2022

Organization

Oak Ridge National Laboratory

Contact

Hong Wang

865.574.5601

Authors

Hong Wang

Oak Ridge National Laboratory

Jy-An Wang

Oak Ridge National Laboratory

Yarom Polsky

Oak Ridge National Laboratory

Fei Ren

Temple University

Viren Thakore

Temple University

Research Areas

DOE Project Details

Project Name Foam Fracturing Study for Stimulation Development of Enhanced Geothermal System (EGS)

Project Lead Zachary Frone

Project Number FY19 AOP 1.3.2.7.

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