Local Seismicity in the Exploitation of Los Humeros Geothermal Field, Mexico

Abstract

During the last decade of seismic monitoring in Los Humeros Geothermal Field in Mexico, a large number of events have been observed around the exploitation area in the north side of the field, an area of high pressure and temperature, which concentrate the leading rate of production and injection in the field. A major earthquake in 2002 (Mw=3.2) were followed with a considerably increased in production, due to high permeability paths towards the vicinity of the wells, also a proportional relationship between the increase of injection and the number of events observed in the local seismic network, related to local induced stresses and directions changes. A study is conducted to determined fractured zones, interpolating the hypocenters and magnitude of the earthquakes with a Kriging Algorithm, it’s possible to associate an area of high energy, this area is been observed at the center of the most productive wells and 250 meters from mayor faults, this zone is also correlated with seismic anisotropy observed in the nearest seismic stations, focal mechanism and reservoir temperature, confirming stress changes due to fluid injection/extraction, and possible fracture propagation. The temperature interval of 310 to 395 ºC presents a large number of micro-earthquakes associated, also large activity in the productive permeable horizons identifies in the reservoir.