Magnetotelluric monitoring of permeability enhancement at enhanced geothermal system project

Abstract Magnetotelluric (MT) data were collected across the Habanero Enhanced Geothermal System (EGS) project in the Cooper Basin, South Australia. A baseline regional MT survey consisting of two profiles were collected to delineate subsurface resistivity structure. An MT monitoring survey was conducted during stimulation of the Habanero-4 well. Inversions of the MT data in 2-D reveal three main resistivity layers to a depth of 5 km. The surface layer is ≤6 Ωm, 1.5 km thick, and composed of poorly consolidated sediments of Lake Eyre and Eromanga Basins. The second layer is ≤25 Ωm, 2 km thick, and correlated to consolidated Cooper Basin sediments. A high resistivity zone below depths of 3.5 km is interpreted as the hot intrusive granodiorite of the Big Lake Suite related to the Habanero EGS reservoir. The second MT survey was conducted during stimulation of Habanero-4, where 36.5 million liters (ML) of water with a resistivity of 13 Ωm was injected over 14 days. Analysis of pre- and post-injection residual phase tensors show possible conductive fractures oriented in a N-S direction for periods greater than 10 s. Apparent resistivity maps also revealed that injected fluids possibly propagated towards N-S direction. This result is in agreement with micro-seismic events observed at the Habanero EGS during fluid injection. The MT responses close to injection show on average 5% decrease in apparent resistivity for periods greater than 10 s. The main reasons for observing subtle changes in resistivity at Habanero EGS is the screening effect of the conductive thick sedimentary cover. Analysis of time-lapse models indicate an increase in total conductance of about 25 S in the N-S direction, which likely indicate anisotropic permeability generated by hydraulic stimulation. Overall, the MT monitoring at Habanero EGS highlights the need for favorable geological settings and/or controlled source and downhole EM methods to measure significant changes in resistivity in EGS reservoirs.

[1]  Nicolas Cuenot,et al.  Analysis of the Microseismicity Induced by Fluid Injections at the EGS Site of Soultz-sous-Forêts (Alsace, France): Implications for the Characterization of the Geothermal Reservoir Properties , 2008 .

[2]  P. Rose,et al.  Tracer testing at the Habanero EGS site, central Australia , 2016 .

[3]  Kerry Key,et al.  1D inversion of multicomponent, multifrequency marine CSEM data: Methodology and synthetic studies for resolving thin resistive layers , 2009 .

[4]  M. Paterson,et al.  Porosity and permeability evolution during hot isostatic pressing of calcite aggregates , 1994 .

[5]  Lars Krieger,et al.  MTpy: A Python toolbox for magnetotellurics , 2014, Comput. Geosci..

[6]  M. Sandiford,et al.  Origin of the in situ stress field in south‐eastern Australia , 2004 .

[7]  S. Baisch,et al.  Continued Geothermal Reservoir Stimulation Experiments in the Cooper Basin (Australia) , 2015 .

[8]  Alan D. Chave,et al.  Bounded influence magnetotelluric response function estimation , 2004 .

[9]  R. Hillis,et al.  Constraining stress magnitudes using petroleum exploration data in the Cooper-Eromanga Basins, Australia , 2006 .

[10]  S. Thiel,et al.  Magnetotelluric monitoring of a fluid injection: Example from an enhanced geothermal system , 2012 .

[11]  H. Keppler,et al.  Monitoring and interpretation of seismic observations in hot dry rock geothermal energy systems , 1987 .

[12]  S. Thiel,et al.  Magnetotelluric imaging of upper crustal partial melt at Tendaho graben in Afar, Ethiopia , 2014 .

[13]  C. Harvey,et al.  UNDERSTANDING THE RESISTIVITIES OBSERVED IN GEOTHERMAL SYSTEMS , 2000 .

[14]  K. Árnason,et al.  Resistivity structure of the upper crust in Iceland , 1985 .

[15]  John R. Booker,et al.  The Magnetotelluric Phase Tensor: A Critical Review , 2013, Surveys in Geophysics.

[16]  A. K. Agarwal,et al.  Characterization of the magnetotelluric tensor in terms of its invariants , 2000 .

[17]  M. H. Waxman,et al.  Electrical Conductivities in Oil-Bearing Shaly Sands , 1968 .

[18]  R. Hillis,et al.  Present-day stresses, seismicity and Neogene-to-Recent tectonics of Australia's ‘passive’ margins: intraplate deformation controlled by plate boundary forces , 2008 .

[19]  S. Thiel,et al.  Three dimensional conductivity model of the Tendaho High Enthalpy Geothermal Field, NE Ethiopia , 2015 .

[20]  R. Hillis,et al.  Maximum horizontal stress orientations in the Cooper Basin, Australia: implications for plate-scale tectonics and local stress sources , 2004 .

[21]  William Rodi,et al.  Nonlinear conjugate gradients algorithm for 2-D magnetotelluric inversion , 2001 .

[22]  N. Horspool,et al.  Using constrained gravity inversions to identify high-heat-producing granites beneath thick sedimentary cover in the Cooper Basin region of central Australia , 2014 .

[23]  P. Gunn,et al.  The nature of the basement to the Cooper Basin region, South Australia , 2000 .

[24]  Scott D. Reynolds,et al.  The Australian Stress Map , 1998, Journal of the Geological Society.

[25]  Peter A. Goode,et al.  Influence of temperature on electrical conductivity on shaly sands , 1992 .

[26]  Sadiq J. Zarrouk,et al.  Numerical model of the Habanero geothermal reservoir, Australia , 2015 .

[27]  S. Thiel,et al.  Characterisation of induced fracture networks within an enhanced geothermal system using anisotropic electromagnetic modelling , 2014 .

[28]  H. Bibby,et al.  Melt distribution beneath a young continental rift: The Taupo Volcanic Zone, New Zealand , 2007 .

[29]  R. Dipippo.  Enhanced Geothermal Systems—Projects and Plants , 2013 .

[30]  Gerard Muñoz,et al.  Exploring for Geothermal Resources with Electromagnetic Methods , 2013, Surveys in Geophysics.

[31]  Thomas Kalscheuer,et al.  Probabilistic 3-D time-lapse inversion of magnetotelluric data: application to an enhanced geothermal system , 2015 .

[32]  K. Árnason,et al.  The Role of Electrical Interface Conduction in Geothermal Exploration , 2005 .

[33]  S. Thiel,et al.  Mapping fractures using 1D anisotropic modelling of magnetotelluric data: a case study from the Otway Basin, Victoria, Australia , 2015 .

[34]  Andreas Junge,et al.  Characterization of and correction for cultural noise , 1996 .

[35]  Graham Heinson,et al.  Time-lapse magnetotelluric monitoring of an enhanced geothermal system , 2013 .

[36]  Eva Schill,et al.  2-D Magnetotellurics at the geothermal site at Soultz-sous-Forêts: Resistivity distribution to about 3000 m depth , 2010 .

[37]  H. Bibby,et al.  The magnetotelluric phase tensor , 2004 .

[38]  Jeffrey S. Ovall,et al.  A parallel goal-oriented adaptive finite element method for 2.5-D electromagnetic modelling , 2011 .

[39]  Adele Manzella,et al.  Electromagnetic sounding of geothermal zones , 2009 .

[40]  G. Beardsmore.  The Influence of Basement on Surface Heat Flow in the Cooper Basin , 2004 .

[41]  Isabelle Lecomte,et al.  Monitoring of induced seismicity during the first geothermal reservoir stimulation at Paralana, Australia , 2014 .

[42]  K. Tietze,et al.  Electromagnetic Monitoring of the Propagation of an Injected Polymer for Enhanced Oil Recovery in Northern Germany , 2014 .

[43]  G. E. Archie.  The electrical resistivity log as an aid in determining some reservoir characteristics , 1942 .

[44]  Albert Genter,et al.  Permeability creation and damage due to massive fluid injections into granite at 3.5 km at Soultz: 1. Borehole observations , 2005 .

[45]  K. Spitzer,et al.  Electromagnetic methods for exploration and monitoring of enhanced geothermal systems – A virtual experiment , 2015 .

[46]  P. Bedrosian,et al.  Electromagnetic monitoring of the Groβ Schönebeck stimulation experiment , 2003 .

[47]  H. Kaieda,et al.  Permeability characterization of the Soultz and Ogachi large-scale reservoir using induced microseismicity , 2002 .

[48]  Susan Petty,et al.  Microseismic monitoring of Newberry volcano EGS demonstration. , 2013 .

[49]  Gary D. Egbert,et al.  ModEM: A modular system for inversion of electromagnetic geophysical data , 2014, Comput. Geosci..

[50]  Greg Stillman,et al.  A TECHNOLOGY ROADMAP FOR STRATEGIC DEVELOPMENT OF ENHANCED GEOTHERMAL SYSTEMS , 2013 .

[51]  Alan G. Jones,et al.  The magnetotelluric method : theory and practice , 2012 .

[52]  César R. Chamorro,et al.  Enhanced geothermal systems in Europe: An estimation and comparison of the technical and sustainable potentials , 2014 .

[53]  C. Barton,et al.  Habanero Field - Structure and State of Stress , 2015 .

[54]  D. Moos,et al.  GEOMECHANICALLY COUPLED SIMULATION OF FLOW IN FRACTURED RESERVOIRS , 2013 .