Foam Fracturing Study for Stimulation Development of Enhanced Geothermal Systems

Description

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.

Resources

Name Format Description Link
57 The zipped folder contains information with post-test specimen images for granite fracturing with foam and water as described in the technical report: Wang, H., Wang, J.-A. J., Polsky, Y., Ren, F., Thakore, V., Foam Fracturing Data with Cyclic Injection for Waterless Stimulation Development of Enhanced Geothermal Systems, ORNL/TM-2022/ 1846, April 2022, Oak Ridge National Laboratory, Oak Ridge, TN. The following are included: 1) Document (.docx) for the designation of file name 2) Image file folder (ims) with images of post- test specimens (.bmp) https://gdr.openei.org/files/1378/post%20test%20specimen%20images%20for%20fracturing%20tests.zip
33 This is a final technical report of the project. The report describes the research activities with foam fracturing testing system and foam fracturing testing at ORNL, and with foam testing and characterization at Temple University. https://gdr.openei.org/files/1378/FTR%20EGS%20Foam%20Frac%20_vf.pdf
57 The zipped folder contains data with granite fracturing for both foam and water, and is composed of following: 1) Excel file(.xlsx) with two data tabs for test conditions of monotonic injection and cyclic injection 2) Timed data folder for injection tests (tds, .csv) 3) Document (.docx) with units of all channels https://gdr.openei.org/files/1378/time%20data%20for%20foam_water%20fracturing%20tests.zip

Tags

  • data
  • sample-data
  • foam-fracturing
  • blind-borehole
  • test
  • egs
  • enhanced-geothermal-systems
  • fatigue
  • fracturing
  • waterless-stimulation
  • time-data
  • stress
  • foam
  • simulation
  • geothermal
  • energy
  • foam-stability

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