2:00 PM - 2:15 PM
[SVC33-02] Seismic measurements using optical fiber DAS around the Mori geothermal power plant in Japan
Keywords:Geothermal exploration, supercritical water, DAS, Nigorigawa caldera, migration imaging, geothermal reservoir
Abstract
In 2021, we carried out a new seismic experiment using DAS at the Mori geothermal power plant owned by Hokkaido Electric Co. The power plant can generate 25 MW of electricity. The Mori geothermal power plant locates in Nigorigawa district of Mori town. We obtained the DAS data using the optical fiber in the F-01 borehole down to 2,000m depth. Nigorigawa is a caldera basin. Most of the geothermal boreholes are in the Nigoragawa caldera. We used a vibrator source at eight locations.
The velocity depth profile fits the caldera structure obtained by Kurozumi and Doi (2003). We also calculated synthetic DAS waveforms, but they do not show discontinuous arrivals around 1,000m depth. If we put a water layer of 250m long and 50m thick at 1,060m depth, the synthetic waveforms show similar discontinuous arrivals at 1,000m. We made migrations using reflected waveforms of DAS records. The reflecting image is dense between 2,000m and 3,000m corresponding to the production zone. The model has an aquifer at 1,000m is explained by the injection zones and total circulation loss observed by drilling of F-01 borehole.
Acknowledgments
The New Energy and Industrial Technology Development Organization (NEDO) supports this study. We greatly appreciate Hokkaido Electric Power Corporation's permission to conduct fieldwork at their power plant. We also thank WELMA Co., Ltd., Hanshin Consultants Co. and KGE Co. for their assistance with data acquisition.
References
Hartog, A. H. 2017, An introduction to distributed optical fiber sensors, RC Press.440. pp.
Kasahara, J., Hasada, Y., and Yamaguchi, T., 2019a, Seismic imaging of supercritical geothermal reservoir using full-waveform inversion method, Proceedings, 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA.
Kasahara, J., Hasada, Y, Kuzume, H., Fujise, Y. and Yamaguchi, T., 2019b, Seismic feasibility study to identify supercritical geothermal reservoirs in a geothermal borehole using DTS and DAS, EAGE extended abstract, EAGE 2019 Annual meeting, London.
Kasahara, J., Hasada, Y., Kuzume, H., Mikada, H., and Fujise, Y., 2020a, The second seismic study at the geothermal field in southern Kyushu, Japan using an optical fiber system and surface geophones, 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA.
Kasahara, J., Hasada, Y., and Kuzume, H., 2020b, Possibility of high Vp/Vs zone in the geothermal filed suggested by the P-to-S conversion, 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA.
Kasahara, J., Hasada, Y., Kuzume, H., Mikada, H., and Fujise, Y., (2021) A DAS-VSP Study Around the Geothermal Field of the Ohnuma Geothermal Power Plant in Northern Honshu, Japan, 46th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA. SGP-TR218.
Kurozumi, H., and Doi, N. 2003, Inner Structure of the Nigorikawa Caldera, Hokkaido, Japan, Bull. Volcanology Society Japan, III, 48, 259-274 (in Japanese).
NEDO, 2008, 2009, 2010, Report of Geothermal Development Promotion, East of Ikeda Lake No. C-2-10, First, Second and Third phases.
In 2021, we carried out a new seismic experiment using DAS at the Mori geothermal power plant owned by Hokkaido Electric Co. The power plant can generate 25 MW of electricity. The Mori geothermal power plant locates in Nigorigawa district of Mori town. We obtained the DAS data using the optical fiber in the F-01 borehole down to 2,000m depth. Nigorigawa is a caldera basin. Most of the geothermal boreholes are in the Nigoragawa caldera. We used a vibrator source at eight locations.
The velocity depth profile fits the caldera structure obtained by Kurozumi and Doi (2003). We also calculated synthetic DAS waveforms, but they do not show discontinuous arrivals around 1,000m depth. If we put a water layer of 250m long and 50m thick at 1,060m depth, the synthetic waveforms show similar discontinuous arrivals at 1,000m. We made migrations using reflected waveforms of DAS records. The reflecting image is dense between 2,000m and 3,000m corresponding to the production zone. The model has an aquifer at 1,000m is explained by the injection zones and total circulation loss observed by drilling of F-01 borehole.
Acknowledgments
The New Energy and Industrial Technology Development Organization (NEDO) supports this study. We greatly appreciate Hokkaido Electric Power Corporation's permission to conduct fieldwork at their power plant. We also thank WELMA Co., Ltd., Hanshin Consultants Co. and KGE Co. for their assistance with data acquisition.
References
Hartog, A. H. 2017, An introduction to distributed optical fiber sensors, RC Press.440. pp.
Kasahara, J., Hasada, Y., and Yamaguchi, T., 2019a, Seismic imaging of supercritical geothermal reservoir using full-waveform inversion method, Proceedings, 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA.
Kasahara, J., Hasada, Y, Kuzume, H., Fujise, Y. and Yamaguchi, T., 2019b, Seismic feasibility study to identify supercritical geothermal reservoirs in a geothermal borehole using DTS and DAS, EAGE extended abstract, EAGE 2019 Annual meeting, London.
Kasahara, J., Hasada, Y., Kuzume, H., Mikada, H., and Fujise, Y., 2020a, The second seismic study at the geothermal field in southern Kyushu, Japan using an optical fiber system and surface geophones, 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA.
Kasahara, J., Hasada, Y., and Kuzume, H., 2020b, Possibility of high Vp/Vs zone in the geothermal filed suggested by the P-to-S conversion, 44th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA.
Kasahara, J., Hasada, Y., Kuzume, H., Mikada, H., and Fujise, Y., (2021) A DAS-VSP Study Around the Geothermal Field of the Ohnuma Geothermal Power Plant in Northern Honshu, Japan, 46th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA. SGP-TR218.
Kurozumi, H., and Doi, N. 2003, Inner Structure of the Nigorikawa Caldera, Hokkaido, Japan, Bull. Volcanology Society Japan, III, 48, 259-274 (in Japanese).
NEDO, 2008, 2009, 2010, Report of Geothermal Development Promotion, East of Ikeda Lake No. C-2-10, First, Second and Third phases.