Influence of permeability anisotropy on heat transfer and permeability evolution in geothermal reservoir

Janim Joshua Ijeje, Quan Gan, Jianchao Cai

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Abstract


Extracting heat energy from geothermal reservoirs essentially relies on circulating cold fluid within fractured hot rocks. The intrinsic anisotropic permeability in the reservoir directly affects the path of flow and the associated thermal drawdown from cooling procedure. Consequently, each individual component including thermal, hydraulic, and mechanical field needs to be considered, to evaluate the influence of permeability anisotropy on the thermal production and evolution of rock properties. In this work, the fully implicit coupled simulator TFReact was successfully implemented to generate results prototypical of an enhanced geothermal system. Anisotropic permeability values were generated from the variation of fracture spacing at three orthogonal principal directions, with identical initial fracture aperture. Five case scenarios of permeability anisotropy were simulated to evaluate the influence of anisotropic thermal drawdown in triggering permeability evolution. Analysis of the propagation of the thermal front from injector to producer indicated that low anisotropic permeability values will lead to late cold water breakthrough at producer, slower migration rate and wider sweep area than high anisotropic permeability values. Isotropic permeability scenario showed a lower thermal gradient profile, comparing against the scenarios of anisotropic permeability. The anisotropic value of 0.01 produced the highest power output, while isotropic permeability generated the least power output. Induced thermal stress resulted an unloading response by reducing compressive normal stress in sub-horizontal direction, and thereby increase fracture aperture in sub-horizontal direction. Invariably, the induced thermal expansion stress increased the compressive stress and reduced fracture aperture and permeability. After the same timing of injection-production cycle, the highest anisotropic permeability scenario resulted a factor of 2.5 increment in evolving fracture permeability, while lowest anisotropic permeability scenario lead to a factor of 0.35 decrease in changing fracture permeability. The generated thermal output suggested the most favorable strategy in maximizing thermal sweep across the reservoir, by prompting thermal transfer normal to direction of injector-producer.

Cited as: Ijeje, J.J., Gan, Q., Cai, J. Influence of permeability anisotropy on heat transfer and permeability evolution in geothermal reservoir. Advances in Geo-Energy Research, 2019, 3(1): 43-51, doi: 10.26804/ager.2019.01.03


Keywords


Permeability anisotropy, fracture aperture, thermal drawdown, geothermal reservoir

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References


Bagalkot, N., Kumar, G.S. Thermal front propagation in variable aperture fracture-matrix system: A numerical study. Sadhana 2015, 40(2): 605-622.

Bodvarsson, G. On the temperature of water flowing through fractures. J. Geophys. Res. 1969, 74(8): 1987-1992.

B ¨odvarsson, G.S., Tsang, C.F. Injection and thermal break-through in fractured geothermal reservoirs. J. Geophys. Res. Sol. Ea. 1982, 87(B2): 1031-1048.

Elsworth, D. Theory of thermal recovery from a spherically stimulated hot dry rock reservoir. J. Geophys. Res. Sol. Ea. 1989, 94(B2): 1927-1934.

Gan, Q., Elsworth, D. Analysis of fluid injection-induced fault reactivation and seismic slip in geothermal reservoirs: Seismic slip induced by thermal stress. J. Geophys. Res.-Sol. Ea. 2014a, 119(4): 3340-3353.

Gan, Q., Elsworth, D. Thermal drawdown and late-stage seismic-slip fault reactivation in enhanced geothermal reservoirs: Thermal front propagation and fault slip. J. Geophys. Res. Sol. Ea. 2014b, 119(12): 8936-8949.

Gan, Q., Elsworth, D. A continuum model for coupled stress and fluid flow in discrete fracture networks. Geomech. Geophys. Geo-Energy Geo-Resour. 2016a, 2(1): 43-61.

Gan, Q., Elsworth, D. Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling. Geothermics 2016b, 62: 131-142.

Gringarten, A.C., Witherspoon, P.A., Ohnishi, Y. Theory of heat extraction from fractured hot dry rock. J. Geophys. Res. 1975, 80(8): 1120-1124.

Itasca. FLAC3D: Fast lagrangian analysis of continua in 3 dimensions-version 4.0. Minneapolis, Minnesota: Itasca Consulting Group, 2009.

Jahediesfanjani, H., Civan, F. Improving performance of the naturally fractured carbonate reservoirs by means of various stimulation and completion techniques. Paper SPE 103986 Presented at the International Oil Conference and Exhibition, Cancun, Mexico, 31 August-2 September, 2006.

Kolditz, O., Clauser, C. Numerical simulation of flow and heat transfer in fractured crystalline rocks: Application to the Hot Dry Rock site in Rosemanowes (UK). Geothermics 1998, 27(1): 1-23.

Min, K.B., Rutqvist, J., Elsworth, D. Chemically and mechanically mediated influences on the transport and mechanical characteristics of rock fractures. Int. J. Rock Mech. Min. 2008, 46(1): 80-89.

Pruess, K. Heat transfer in fractured geothermal reservoirs with boiling. Water Resour. Res. 1983, 19(1): 201-208.

Pruess, K. The TOUGH codes-A family of simulation tools for multiphase flow and transport processes in permeable media. Vadose Zone J. 2004, 3(3): 738-746.

Rutqvist, J., Stephansson, O. The role of hydromechanical coupling in fractured rock engineering. Hydrogeol. J. 2003, 11(1): 7-40.

Sandwell, D.T. Thermal stress and the spacings of transform faults. J. Geophys. Res. 1986, 91(B6): 6405.

Snow, D.T. Anisotropie permeability of fractured media. Water Resour. Res. 1969, 5(6): 1273-1289.

Taron, J., Elsworth, D. Thermal-hydrologic-mechanical-chemical processes in the evolution of engineered geothermal reservoirs. Int. J. Rock Mech. Min. 2009, 46(5): 855-864.

Taron, J., Elsworth, D. Coupled mechanical and chemical processes in engineered geothermal reservoirs with dynamic permeability. Int. J. Rock Mech. Min. 2010, 47(8): 1339-1348.

Taron, J., Elsworth, D., Min, K.B. Numerical simulation of thermal-hydrologic-mechanical-chemical processes in deformable, fractured porous media. Int. J. Rock Mech. Min. 2009, 46(5): 842-854.

Watanabe, K., Takahashi, H. Fractal geometry characterization of geothermal reservoir fracture networks. J. Geophys. Res. Sol. Ea. 1995, 100(B1): 521-528.

Witherspoon, P.A., Wang, J.S.Y., Iwai, K., et al. Validity of Cubic Law for fluid flow in a deformable rock fracture. Water Resour. Res. 1980, 16(6): 1016-1024.


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