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2018 Vol.28, Issue 5 Preview Page
October 2018. pp. 400-425
Abstract

This study presents the research results and current status of the DECOVALEX-2019 project Task B. Task B named ‘Fault slip modelling’ is aiming at developing a numerical method to simulate the coupled hydro-mechanical behavior of fault, including slip or reactivation, induced by water injection. The first research step of Task B is a benchmark simulation which is designed for the modelling teams to familiarize themselves with the problem and to set up their own codes to reproduce the hydro-mechanical coupling between the fault hydraulic transmissivity and the mechanically-induced displacement. We reproduced the coupled hydro-mechanical process of fault slip using TOUGH-FLAC simulator. The fluid flow along a fault was modelled with solid elements and governed by Darcy's law with the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by creating interface elements between two separating rock blocks in FLAC3D. A methodology to formulate the hydro-mechanical coupling relations of two different hydraulic aperture models and link the solid element of TOUGH2 and the interface element of FLAC3D was suggested. In addition, we developed a coupling module to update the changes in geometric features (mesh) and hydrological properties of fault caused by water injection at every calculation step for TOUGH-FLAC simulator. Then, the transient responses of the fault, including elastic deformation, reactivation, progressive evolutions of pathway, pressure distribution and water injection rate, to stepwise pressurization were examined during the simulations. The results of the simulations suggest that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing collaboration and interaction with other research teams of DECOLVAEX-2019 Task B and validated using the field data from fault activation experiments in a further study.

본 논문에서는 국제공동연구인 DECOVALEX-2019 프로젝트 Task B의 연구결과와 현황을 소개하였다. Task B의 주제는 ‘Fault slip modelling’으로 유체의 주입으로 인해 발생하는 단층의 재활성(미끄러짐, 전단파괴)과 수리역학적 거동을 예측할 수 있는 해석기법을 개발하는 데에 그 목적이 있다. 1단계 연구는 참가팀들이 연구주제에 대해 숙지하고, 벤치마크 모델을 대상으로 단층의 투수특성과 역학적 거동의 상호작용을 모사할 수 있는 해석코드를 개발할 수 있도록 하는 준비 단계의 연구이다. 본 연구에서는 TOUGH-FLAC 연동해석 기법을 사용하여 물 주입으로 인한 단층의 수리역학적 연계거동을 모사하였다. TOUGH2 해석에서는 단층을 Darcy의 법칙과 삼승법칙을 따르는 연속체 요소로 모델링하였으며, FLAC3D 해석에서는 미끄러짐과 개폐가 허용되는 불연속 인터페이스 요소를 통해 모사하였다. 두 가지 수리간극모델에 대하여 수리역학적 커플링 관계식을 수치화하였으며, 연속체 요소(수리모델)와 인터페이스 요소(역학모델)의 거동을 연계할 수 있는 해석기법을 제시하였다. 또한, 단층의 역학적 변형(간극의 변화)으로 인한 수리물성 변화와 기하학적 변화(해석 메쉬의 변형)를 수리해석에 반영할 수 있는 해석기법을 개발하였다. 다양한 압력의 물을 단계적으로 주입하고 이로 인해 유도되는 단층의 탄성거동 및 전단파괴(미끄러짐)에 대해 살펴보았으며, 수리간극의 변화 양상과 원인, 압력 분포와 주입율의 관계 등을 면밀히 검토하였다. 해석 결과, 본 연구에서 개발한 해석기법이 물 주입으로 인한 단층의 미끄러짐 거동을 합리적인 수준에서 재현할 수 있는 것으로 판단할 수 있었다. 본 연구의 해석모델은 Task B에 참여하는 국외 연구팀들과의 의견 교류와 워크숍을 통해 지속적으로 개선하는 한편, 향후 연구의 현장시험에 적용하여 타당성을 검증할 예정이다.

References
  1. Bohloli, B., Choi, J.C., Skurtveit, E., Grande, L., Park, J., Vannest, M., 2015, Criteria of fault geomechanical stability during a pressure buildup, IEAGHG report 2015/04. Cheltenham, UK.
  2. Cappa, F., Rutqvist, J., 2011, Modeling of coupled deformation and permeability evolution during fault reactivation induced by deep underground injection of CO2, International Journal of Greenhouse Gas Control, Vol. 5, pp. 336-346.10.1016/j.ijggc.2010.08.005
  3. Cuisiat, F., Jostad, H.P., Andresen, L., Skurtveit, E., Skomedal, E., Hettema, M., Lyslo, K., 2010, Geomechanical integrity of sealing faults during depressurization of the Statfjord field, Journal of Structural Geology, Vol. 32, pp. 1754-1767.10.1016/j.jsg.2010.01.006
  4. Gudmundsson, A., 2004, Effects of Young's modulus on fault displacement. Comptes Rendus Geoscience, Vol. 336, pp. 85-92.10.1016/j.crte.2003.09.018
  5. Guglielmi, Y., 2016, In-situ clay faults slip hydro-mechanical characterization (FS experiment), Mont Terri underground rock laboratory. Lawrence Berkeley National Laboratory, Report LBNL-XXXX March.
  6. Guglielmi, Y., Cappa, F., Lancon, H., Janowczyk, J., Rutqvist, J., Tsang, C.-F., Wang, J. S. Y., 2014, ISRM suggested method for Step-Rate Injection Method for Fracture In-Situ Properties (SIMFIP): Using a 3-components borehole deformation sensor. Rock Mechanics and Rock Engineering, Vol. 47, pp. 303-311.10.1007/s00603-013-0517-1
  7. Guglielmi, Y., Elsworth, D., Cappa, F., Henry, P., Gout, C., Dick, P., Durand, J., 2015, In situ observations on the coupling between hydraulic diffusivity and displacements during fault reactivation in shales, Journal of Geophysical Research: Solid Earth, Vol. 120, pp. 7729-7748.10.1002/2015JB012158
  8. Kim, H.M., Rutqvist, J., Ryu, D.W., Choi, B.H., Sunwoo, C., Song, W.K., 2012, Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A modeling study of air tightness and energy balance, Applied Energy, Vol. 92, pp. 653-667.10.1016/j.apenergy.2011.07.013
  9. Leijon, B., 1993, Mechanical properities of fracture zones, SKB Technical Report TR 93-19.
  10. Morris, J.P., Hao, Y., Foxall, W., McNab, W., 2011, A study of injection-induced mechanical deformation at the In Salah CO2 storage project, International Journal of Greenhouse Gas Control, Vol. 5, pp. 270-280.10.1016/j.ijggc.2010.10.004
  11. Orlic, B., Heege, J., Wassing B., 2011, Assessing the integrity of fault- and top seals at CO2 storage sites, Energy Procedia, Vol. 4, pp. 4798-4805.10.1016/j.egypro.2011.02.445
  12. Park, J.W., Rutqvist, J., Ryu, D.W., Park, E.S., Synn, J.H., 2016, Coupled thermal-hydrological-mechanical behavior of rock mass surrounding a high-temperature thermal energy storage cavern at shallow depth, International Journal of Rock Mechanics & Mining Sciences, Vol. 83, pp. 149-161.10.1016/j.ijrmms.2016.01.007
  13. Rinaldi, A.P., Rutqvist, J., Cappa, F., 2014, Geomechanical effects on CO2 leakage through fault zones during large-scale underground injection, International Journal of Greenhouse Gas Control, Vol. 20, pp. 117-131.10.1016/j.ijggc.2013.11.001
  14. Rutqvist, J., 2012, Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations, Computers & Geosciences, Vol. 37, pp. 739-750.10.1016/j.cageo.2010.08.006
  15. Rutqvist, J., Dobson, P.F., Garcia, J., Hartline, C., Jeanne, P., Oldenburg, C.M., Vasco, D.W., Walters, M., 2015, The northwest Geysers EGS demonstration project, California: Pre-stimulation modeling and interpretation of the stimulation. Mathematical Geosciences, Vol. 47, pp. 3-29.10.1007/s11004-013-9493-y
  16. Rutqvist, J., Rinaldi, A.P., Cappa, F., Moridis, G.J., 2013, Modeling of fault reactivation and induced seismicity during hydraulic fracturing of shale-gas reservoirs, Journal of Petroleum Science and Engineering, Vol. 107, pp. 31-44.10.1016/j.petrol.2013.04.023
  17. Rutqvist, J., Tsang, C.F., 2012, Multiphysics processes in partially saturated fractured rock: Experiments and models from Yucca Mountain. Reviews of Geophysics, Vol. 50, RG3006.10.1029/2012RG000391
  18. Rutqvist, J., Wu, Y-S. Tsang, C.F., Bodvarsson, G., 2002, A modeling approach for analysis of coupled multiphase fluid flow, heat transfer, and deformation in fractured porous rock, International Journal of Rock Mechanics and Mining Sciences, Vol. 39, pp. 429-442.10.1016/S1365-1609(02)00022-9
  19. Tsang, C.F., Birkholzer, J., Rutqvist, J., 2008, A comparative review of hydrologic issues involved in geologic storage of CO2 and injection disposal of liquid waste, Journal of Environmental Geology, Vol. 54, pp. 1723-1737.10.1007/s00254-007-0949-6
  20. Vidal-Gilbert, S., Nauroy, J.-F., Brosse, E., 2009, 3D geomechanical modelling for CO2 geologic storage in the Dogger carbonates of the Paris Basin. International Journal of Greenhouse Gas Control, Vol. 3, pp. 288-299.10.1016/j.ijggc.2008.10.004
  21. Vidal-Gilbert, S., Tenthorey, E., Dewhurst, D., Ennis-King, J., Van Ruth, P., Hillis, R., 2010, Geomechanical analysis of the Naylor Field, Otway Basin, Australia: implications for CO2 injection and storage, International Journal of Greenhouse Gas Control, Vol. 4, pp. 827-839.10.1016/j.ijggc.2010.06.001
  22. Wiprut, D.J., Zoback, M.D., 2002, Fault reactivation, leakage potential, and hydrocarbon column heights in the northern North Sea, In: Hydrocarbon seal quantification, NPF Special Publication, Vol. 11, pp. 203-219.10.1016/S0928-8937(02)80016-9
  23. Witherspoon, P.A., Wang, J.S.Y., Iwai, K., Gale, J.E., 1980, Validity of cubic law for fluid flow in a deformable rock fracture, Water Resources Research, Vol. 16, pp. 1016-1024.10.1029/WR016i006p01016
Information
  • Publisher :Korean Society for Rock Mechanics and Rock Engineering
  • Publisher(Ko) :한국암반공학회
  • Journal Title :Tunnel and Underground Space
  • Journal Title(Ko) :터널과 지하공간
  • Volume : 28
  • No :5
  • Pages :400-425
  • Received Date :2018. 08. 30
  • Accepted Date : 2018. 09. 17