An analysis of local seismicity within the Klyuchevskoi Volcanic Cluster and Shiveluch Volcano for the period 2000–2017 revealed a sequence of plane-oriented earthquake clusters that are interpreted here as the emplacement of dikes and sills (magmatic fracking). The geometry of magma bodies reflects the geomechanical conditions in volcanic plumbing systems and at the bases of the volcanoes. Magmatic fracking within active magmatic plumbing systems results in the formation of permeable reservoirs whose vertical extent can reach 35 km (Klyuchevskoi) and can be as wide as 15 km across (Shiveluch), depending on the geomechanical condition of the host rocks. These reservoirs will be the arena of subsequent hydrothermal circulation, producing geothermal and ore fields, as well as hydrocarbon fields. TOUGH2-EOS1sc simulation tools were used to estimate the conditions for the formation of hydrothermal reservoirs at temperatures below 1200°С and pressures below 1000 bars.

An analysis of local seismicity within the Avacha–Koryakskii Volcanic Cluster during the 2000–2016 period revealed a sequence of plane-oriented earthquake clusters that we interpret as a process of dike and sill emplacement. The highest magmatic activity occurred in timing with the 2008–2009 steam–gas eruption of Koryakskii Volcano, with magma injection moving afterwards into the cone of Avacha Volcano (2010–2016). The geometry of the magma bodies reflects the NF geomechanical conditions (tension and normal faults, Sv >SHmax >Shmin ) at the basement of Koryakskii Volcano dominated by vertical stresses Sv, with the maximum horizontal stress SHmax pointing north. A CFRAC simulation of magma injection into a fissure under conditions that are typical of those in the basement of Koryakskii Volcano (the angle of dip is 60о, the size is 2 × 2 km2, and the depth is –4 km abs.) showed that when the magma discharge is maintained at the level of 20000 kg/s during 24 hours the fissure separation increases to reach 0.3 m and the magma injection is accompanied by shear movements that occur at a rate as high as 2 × 10–3 m/s, thus corresponding to the conditions of local seismic events with Mw below 4.5. We are thus able to conclude that the use of planeoriented clusters of earthquakes for identification of magma emplacement events is a physically sound procedure. The August 2, 2011 seismicity increase in the area of the Izotovskii hot spring (7 km from the summit of Koryakskii Volcano), which is interpreted as the emplacement of a dike, has been confirmed by an increase in the spring temperature by 10–12°С during the period from October 2011 to July 2012.

A conceptual model of the thermal and water recharge of the Ketkinsky geothermal field as a product of magma and water injection from the Koryaksky volcano located 24 km apart was proposed. A digital hydrogeological model of the Ketkinsky geothermal field was developed in the volume of 7 km x 5 km x 2.5 km (from the topographic surface), it includes the space drilled by exploration and production wells. The model is based on an analysis of 3D distributions of temperature, pressure, salinity and CH4 content, geometrization of productive faults and well productivity characteristics. The geofiltration space was zoned in the model with separation of
deep and shallow productive geothermal reservoirs, the area of deep thermal fluid upflow in the SSE part of the model base and the area of hidden thermal water discharge at the ground surface.
A natural state inversion iTOUGH2-EWASG simulation was performed to estimate the deep thermal water upflow and permeability of productive geothermal reservoirs. The deep thermal water upflow is estimated to be about 10 kg/s, the permeability is estimated to be 190 mD (shallow productive reservoir) and 35 mD (deep productive reservoir). Inverse iTOUGH2-EWASG modeling of the hydrodynamic operating history of 1989–2020 was used to estimate the compressibility of the productive geothermal reservoirs: the compressibility of the deep reservoir is estimated at 7.16E-10 Pa???? 1, the shallow reservoir at 4.14E-07 Pa???? 1. Direct iTOUGH2-EWASG modeling with the above parameters reproduces the history of salinity and temperature changes in production wells.
Forecast modeling of existing producing wells #23, K6, K01, K5 operation for 25 years with application of submersible pumps at immersion depth of 70 m confirms the possibility of their sustainable operation with total flow rate not less than 14.2 kg/s, adding four producing wells may yield to 54.3 kg/s with retaining of produced water quality (temperature, gas content of CH4, salinity).
The use of submersible pumps and reinjection can significantly increase the reserves of Ketkinsky field to 165–175 kg/s of 70–80 ◦C and 60–70 g/s of CH4. Additional increase in reserves may be obtained by drilling the already known thermal anomaly in the SSE sector of the field and in the SWW foothills of Koryaksky volcano.

Mutnovsky Volcano is characterized by predominantly magmatic activity for the last 4 thousand years in the northern sector where the Mutnovsky geothermal field lies. Magmatic activity is identified using the Frac-Digger method based on seismic data as reported by the KB FRC UGS RAS. The most significant sequence of shallow dikes striking northeast has been manifested at the surface by blowing two-phase geothermal wells. Dike emplacement in March 2024 was synchronized with a hydrothermal explosion producing a crater of volume reaching 0.36 million m3 at the place of well 022 (Crater 022+). Unaltered fragments due to the explosion indicate a lithoclastic character in the gas-enriched head of the dike. The bottom of the explosion crater is a hydrothermally altered (opal, zeolite) 160 × 75 m2 in area. The mechanism of the hydrothermal explosion is treated as resulting from hydraulic fracturing by means of a shallow dike, with subsequent increase in pressure in the shallow geothermal reservoir near the well with a closed wellhead control-valve.

Mutnovsky geothermal area in Kamchatka, Russia where 62 MWe GeoPP installed - is a source of geothermal electricity supply, as well as a hazard volcanic area. We used local seismicity micro-earthquakes (MEQ’s) data from 2009 to 2021 to define seismogenic faults beneath and adjacent to Mutnovsky volcano, which interpreted as magma injections in form of dykes and sills. Magma fracking beneath Mutnovsky volcano pointed on shear mode low angle dykes in northeast sector and opening mode geomechanical conditions at -3000 m, where sills in area of 62 km2 are suggested to be formed. Low angle dykes injections were reproduced by hydromechanical simulation using CFRAC, modeling results matches with MEQ’s statistics observed.
Mutnovsky GeoPP steam collection system shows sensitivity to non-condensable gasses (NCG) content (partial gas pressure) variations (2019—2020), that is used as indicator of magmatic gasses recharge via magma fracking volcano system to production geothermal reservoir. Partial gas pressure measured at GeoPP condenser unit. Magma injections associated with NCG (CO2) release in production reservoirs seems to be synchronize with partial NCG pressure excursions at GeoPP condenser. Some signs of magma fracking events were also revealed using discreet observations (2016–2021) on a blowing wells on a foothills of Mutnovsky volcano. Magma fracking beneath Mutnovsky volcano is associate with small and medium hydrothermal explosions and landslide (2009–2021). Magma fracking distributions pointed on a new potentially production geothermal reservoir beneath northeast foothills of Mutnovsky volcano (depth range from -4000 to -2000 m, accessible area of 30 km2).

The Paratunsky and Verkhne-Paratunsky fields (Kamchatka, Russia) are examples of low-temperature nitrogen (LT N2) geothermal systems that are widespread throughout the world and are believed to have formed as a result of penetration of meteoric water into deep faults and heat mining from host rocks under background heat flow and temperature gradient conditions. However, no one has tested the geologically long-term thermal recharge capability of such systems to be recharged by heat and water under real 3D environmental conditions. A solution to this unsolved problem has been obtained here using specific examples. The two closely spaced reservoirs are 15 km apart, composed of volcanogenic rocks of Eocene-Quaternary age and characterized by shallow permeability reservoirs underlain by extinct volcanic conductive roots, where 60–90 ◦C thermal N2 SO4–Na waters circulate. The Paratunsky reservoir has a 60-year history of intensive exploitation (150–250 kg/s), while the Verkhne-Paratunsky reservoir is just being brought into development. Application of a simple radial-cylindrical (RZ) model to the Verkhne-Paratunsky geothermal system allowed us to show the principal possibility of formation of a circulating hydrothermal system in a structure with a radius of about 15 km and a circulation depth of -3 km within the first thousand years at a temperature of 60 ◦C and a flow rate of 60 kg/s.
Then a three-dimensional numerical (3D) model of the Verkhne- Paratunsky and Paratunsky low-temperature nitrogen geothermal system was constructed, assuming that the upper part of the pre-Cretaceous basement is a permeable conduit surface and the roots of extinct volcanoes provide vertical down-flow recharge and up-flow discharge of this natural heat and mass circulation system. This numerical model covers all significant thermal discharge features, recharge area of the adjacent highlands. Subsequent modeling confirms the possibility of increasing the temperature to 80 ◦C, diluting the initially brine-saturated NaCl permeable reservoirs and maintaining up-flow rate at observed values for thousands of years from the onset of hydrothermal circulation.