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DE-FG36-04GO14289, M001 October 1, 2004 – December 31, 2007 (3 years)

Stress- and Chemistry-Mediated Permeability Enhancement/Degradation in Stimulated Critically-Stressed Fractures. DE-FG36-04GO14289, M001 October 1, 2004 – December 31, 2007 (3 years) Derek Elsworth, Penn State University, PI Avrami Grader (EGEE, PSU) Chris Marone (Geosciences, PSU)

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DE-FG36-04GO14289, M001 October 1, 2004 – December 31, 2007 (3 years)

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  1. Stress- and Chemistry-Mediated Permeability Enhancement/Degradation in Stimulated Critically-Stressed Fractures DE-FG36-04GO14289, M001 October 1, 2004 – December 31, 2007 (3 years) Derek Elsworth, Penn State University, PI Avrami Grader (EGEE, PSU) Chris Marone (Geosciences, PSU) Phillip Halleck (EGEE, PSU), & Peter Rose, EGI, University of Utah

  2. Purpose • Towards the engineering of “EGS”: • Long-lived • Low-impedance • High heat flow • Consistent understanding of the evolution of flow connections resulting from stimulation • Physical (effective stresses) • Chemical (dissolution/precipitation) • Critical influences of: • Mechanical Influences [THM] • Chemical Influences [THC] • Importance where fractures are “critically stressed” • Resolve anomalous observations THMC

  3. Objectives “… a consistent view of the thermal, hydraulic, mechanical, and chemical processes that influence permeability enhancement….and to be able to apply these principles to EGS reservoir development.” Hydro-Mechanical Hydro-Chemical Constitutive Models Modeling/Upscaling

  4. Plan and Approach Hydro-Mechanical Hydro-Chemical Constitutive Models Modeling/Upscaling

  5. Hydro-Chemical Reactor - Experimental Arrangement

  6. Qmass X-ray CT Qfluid=Constant Apparatus

  7. Typical Response [Polak et al., GRL, 2003]

  8. Experiment Matrix

  9. Hydro-Mechanical Reactor

  10. Slide-Hold-Slide Friction Experiments • Hold periods of 30 – 104 [sec] @20 degree-C, peak coefficient is independent of hold periods @65 degree-C, peak value increases with increase of hold period

  11. Experiment Matrix – Similar to Hydro-Chemical Reactor

  12. Results • Hydro-Chemical Reactor • Hydro-Mechanical Reactor • Modeling

  13. Fractured Limestone – Features of Response (predate this project) 0 hr 1462 hr 0 hr 1462 hr

  14. 1. Hydro-Chemical Reactor

  15. Coso core 64-16 at 646 ft

  16. Typical slice

  17. Thresholded three-dimensional image of the fracture

  18. Three-dimensional image of the large openings of the fracture

  19. Three-dimensional combined image of the large aperture openings and the linking smaller apertures within the core.

  20. 2. Hydro-Mechanical Reactor

  21. 3. Transport and Mechanical Modeling • Goal: • Construct a numerical model to simulate permeability enhancement caused by hydraulic and chemical stimulation – ultimately apply to stimulation at Coso • FLAC3D→ [High Peclet Number Flows] → ToughReact • → Fist step; Focus on a behavior of a single fracture • ─ Mass transport within a fracture • ─ Solve an advection-dispersion equation, complete with a reactive term • ─ FEM, FDM • ─ Accommodate a problem with high Peclet number (advection dominant)

  22. Advection-dispersion equation with high Peclet number A Lagrangian-Eulerian Method Continuous injection

  23. Replicate experimental result (Nova II) 1. Set initial aperture distribution 2. Apply I.C. and B.C. → Obtain velocity distr. in a fracture by solving Reynolds’ equation 3. Dissolution at contact area and free-face (reaction) → Obtain concentration distribution + Modify aperture distribution due to dissolution Iteration 4. Lagrangian-Eulerian method (Advection-diffusion) → Obtain concentration distribution within and out of domain

  24. Replicate experimental result (Nova II) • Numerical model is capable of replicating experiment though prescribed multiplier for dissolution rate constant is relatively large. • Another mechanism instead of pressure solution may be active (mechanical creep?).

  25. Replicate experimental result (Nova II) <Aperture and contact area distribution (after experiment)> CT image Model prediction The model cannot perfectly represent experiment, but predict changes in aperture and contact area distribution with time

  26. Impact/Merit • Project recently initiated • Providing meager data/information that are not well understood, and linking with improved understanding • Stress- and chemistry-mediated influences are potent • High temperatures where few data exist • Current understanding lacking • Linkages and Dissemination • Closely tied to EGI parallel study incl. personnel transfer • Potential isotopic linkages for heat-flow areas (E. Sonnenthal) • Products • Elsworth, D., and Yasuhara, H. (2005) Short timescale chemo-mechanical effects and their influence on the transport properties of fractured rock. Submitted for publication. Earth and Planetary Research Letters. 40 pp. • GRC Meeting September

  27. Completion

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