Active seismic for exploration of SHGS geothermal systems

Active seismic for exploration of SHGS geothermal systems Flavio Poletto(1), Erika Barison(1), Gualtiero Böhm(1) and Biancamaria Farina(1) (1)OGS-Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - Trieste, Italy GEMex CONFERENCE Potsdam, GFZ 18 -19 February 2020 This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 727550 and the Mexican Energy Sustainability Fund CONACYT-SENER, project 2015 -04 -68074. SUPERHOT GEOTHERMAL SYSTEMS AND THE DEVELOPMENT OF EGS www. gemex-h 2020. eu

Outline • Los Humeros (LH) geothermal system and motivation of the work • LH regional and local models used for detection of deep structures • Short description of active-seismic (AS) dataset • Summary of AS depth-processing results and P-velocity model (imaging) • Contribution to geological interpretation of deep structures (WP 5. 2) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Outline • Los Humeros (LH) geothermal system and motivation of the work • LH regional and local models used for detection of deep structures • Short description of active-seismic (AS) dataset • Summary of AS depth-processing results and P-velocity model (imaging) • Contribution to geological interpretation of deep structures (WP 5. 2) • “Integration of methods and inversion constraints” (WP 5. 4) • AS contribution to calibration of passive seismic (PS) results and vice-versa • Use of AS and PS synthetic data for comparison with real AS data • Analysis of active vs passive seismic: Integrated inversion approach • Conclusions and recommendations Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH geothermal system • Los Humeros (LH) geothermal system: situated in the eastern sector of the Trans Mexican Volcanic Belt (TMVB), forming the northern boundary of the Serdán-Oriental basin. • LH is a superhot geothermal system (SHGS) operated by the Comisión Federal de Electricidad (CFE). Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH geothermal system • Los Humeros (LH) geothermal system: situated in the eastern sector of the Trans Mexican Volcanic Belt (TMVB), forming the northern boundary of the Serdán-Oriental basin. • LH is a superhot geothermal system (SHGS) operated by the Comisión Federal de Electricidad (CFE) • LH is one of most important geothermal fields in Mexico, geologically characterized by a caldera complex with a complicated evolution. Modified after Arzate et al. (2018) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH geothermal system and motivation • Motivation: to recover existing geophysical (seismic) information on deep structures, by reprocessing and study of legacy seismic data in the faulted caldera area to obtain detailed images (in the framework of WP 5. 2) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH regional and local models Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH regional and local Active Seismic (AS) models Faults interpretation after Calcagno et al. (2018) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH AS lines (legacy data) parameters q Four 2 D reflection seismic lines (L 2, L 3, L 4 and L 5) acquired with Vibroseis source in 1998 by COMESA for CFE Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

LH AS lines (legacy data) properties q Four 2 D reflection seismic lines (L 2, L 3, L 4 and L 5) acquired with Vibroseis source in 1998 by COMESA for CFE • Variable S/N, waves recorded in complex area • Data acquired with strong pattern filters (~100 -m source, ~92 -m geophone arrays) • Signal analysis at low seismic frequencies • Gap at shorter offsets (-300 m +300 m) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

PSDM processing and inversion flow Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

PSDM processing and inversion flow (Geo. Depth) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

L 5 results: seismic and depth P-velocity model 3 km 2 km 1 km 0 km -1 km Velocity analysis and inversion after horizon’s interpretation (D 5. 3) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina Vp (m/s)

3 D view of L 2, L 3, L 4 and L 5 Vp (m/s) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

New outcomes and L 5 integrated interpretation 3 km 2 km 1 km 0 km -1 km After Carrasco-Núñez et al. , (2017), Norini et al. , (2019) and Lorenzo-Pulido (2008) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

New joint AS and PS approach for SHGS (T 5. 4) q Use 2 D seismic lines (real shot data) as “field experiments” • Verify seismic (AS and PS) models by calculating full-waveform synthetic signals (2 D simulation by 10 m × 10 m grid) • Provide better insight for shallow- and medium-depth structures • Shallow information needed for obtaining correct imaging at depth • AS contribution for depth imaging not only by reflection processing • Approach by “full-waveform analysis” Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Plane view of the tomographic grid (OGS) Passive-stations data Provided by GFZ REFERENCE GRID - Irregular grid used for the definition of the initial model for the tomographic inversion, obtained by two regular grids with different resolutions Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Plane view of the tomographic grid (OGS) Initial GRID dimensions: X= Y 1385 m X= Y 2750 m Z 500 m Staggered GRID: X= Y 485 m Z 250 m Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Plane view of the tomographic grid (OGS) Initial GRID dimensions: X= Y 1385 m X= Y 2750 m Z 500 m Staggered GRID: X= Y 485 m Z 250 m Tomography results depending on the initial model! Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Synthetic results real ‘shot experiment’ Time (s) Offset Real signal Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Synthetic results real ‘shot experiment’ Offset Time (s) Offset Real signal Synthetic signal (AS model) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Synthetic results real ‘shot experiment’ Offset Real signal Offset Time (s) Offset Synthetic signal (AS model) Synthetic signal (PS tomo model) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Synthetic results real ‘shot experiment’ Offset Real signal Offset Synthetic signal (AS model) Offset Time (s) Offset Synthetic signal (PS tomo model) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina Synthetic signal (initial AS + PS tomo model)

Models used for synthetic seismograms of L 5 AS model (Geo. Depth) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Models used for synthetic seismograms of L 5 AS model (Geo. Depth) PS tt-tomo model Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Models used for synthetic seismograms of L 5 AS model (Geo. Depth) PS tt-tomo model AS + PS tt-tomo model Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Models used for synthetic seismograms of L 5 AS model (Geo. Depth) Horizon driven PS tt-tomo model Tomo final grid 500 m × 250 m AS + PS tt-tomo model Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Models used for synthetic seismograms of L 5 AS model (Geo. Depth) PS tt-tomo model AS + PS tt-tomo model Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Conclusions • Active-seismic approach used for detection of deep structures by seismic methods at Los Humeros SHGS (D 5. 3) • Depth model/imaging by reprocessing of active-seismic legacy dataset • Detailed Local model information, i. e. , information on relevant structures • Contribution to geological interpretation of deep and shallow structures Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Conclusions • Active-seismic approach used for detection of deep structures by seismic methods at Los Humeros SHGS (D 5. 3) • Depth model/imaging by reprocessing of active-seismic legacy dataset • Detailed Local model information, i. e. , information on relevant structures • Contribution to geological interpretation of deep and shallow structures • AS contribution to calibration of passive seismic results (D 5. 9) • Passive seismic inversion (tt-tomo) depending on initial conditions! • Analysis of active vs passive synthetic seismic signals (see D 5. 5) • Integrated inversion approach by constraining initial model (AS – PS grid adaption in local model and extrapolation) • Recommendations: consider active-seismic contribution for future SHGS and also EGS applications (D 5. 12) Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

References Arzate, J. , Corbo-Camargo, F. , Carrasco-Núñez, G. , Hernàndez, J. , and Yutsis, V. [2018] The Los Humeros (Mexico) geothermal field model deduced from new geophysical and geological data. Geothermics, 71, 200 -211. Calcagno, P. , Evanno, G. , Trumpy, E. , Gutiérrez-Negrín, L. C. , Macías Vásquez, J. L. , Carrasco Núñez, G. , Liotta, D. (2018) Preliminary 3 -D geological models of Los Humeros and Acoculco geothermal fields (Mexico) – H 2020 GEMex Project, Adv. Geosci. , 45, 321 -333. Carrasco-Núñez, G. , López-Martínez, M. , Hernández, J. , Vargas, V. (2017) Subsurface stratigraphy and its correlation with the surficial geology at Los Humeros geothermal field, eastern Trans. Mexican volcanic belt. Geothermics, 67, 1 -17. Lorenzo-Pulido, C. D. (2008) Borehole geophysics and geology of well H-43, Los Humeros geothermal field, Puebla, México. In: Geothermal Training Programme Report, 9, 23, Orkustofnun, Grensásvegur, Reykjavík, Iceland Norini, G. , Carrasco-Núñez G. , Corbo-Camargo F. , Lermo J. , Rojas J. H. , Castro C. , Bonini M. , Montanari D. , Corti G. , Moratti G. , Piccardi L, Chavez T, Zuluaga M. C. , Ramirez M. , Cedillo F. (2019) The structural architecture of the Los Humeros volcanic complex and geothermal field, Journal of Volcanology and Geothermal Research, 381, 312 -329. Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina

Acknowledgements q We acknowledge the Comisión Federal de Electricidad (CFE) for kindly providing support and advice and for granting access to their geothermal fields. q We thank CFE for the permission to use the legacy active-seismic data and UNAM (Universidad Nacional Autónoma de México) for providing the active -seismic data. q We thank EU GEMex colleagues, in particular GFZ, for providing PS data and information on the geological model of Los Humeros (WP 3) This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 727550 and the Mexican Energy Sustainability Fund CONACYT-SENER, project 2015 -04 -68074 The content of this presentation reflects only the authors’ view. The Innovation and Networks Executive Agency (INEA) is not responsible for any use that may be made of the information it contains. Active seismic for exploration of SHGS geothermal systems F. Poletto, E. Barison, G. Böhm and B. Farina