Los Humeros is a Pleistocene caldera in the eastern portion of the Trans Mexican Volcanic Belt,exploited for geothermal resources for over five decades,presently providing over 90 MWe.We model the gravity field,obtain...Los Humeros is a Pleistocene caldera in the eastern portion of the Trans Mexican Volcanic Belt,exploited for geothermal resources for over five decades,presently providing over 90 MWe.We model the gravity field,obtaining 3D density models from high-resolution(220 m)satellite-derived gravity data and compare these models with geological and magneto-telluric descriptions detailed elsewhere.An additional comparison with a geological E-W section indicates that the most voluminous caldera formations coincide with a low-density region extending from the surface to below 6 km bsl that is likely associated with the caldera activity.Interpretation of three additional density crosssections leads us to infer that the magmatic system feeding Los Humeros also has a component surfacing 12 km north of the center of the caldera,a result that is first disclosed here.Comparison of the density distributions with three corresponding electrical resistivity profiles obtained elsewhere from magnetotelluric soundings shows that low-resistivity regions prevail above 1 km asl where high-density pockets alternate with low-density regions.High-resistivity regions can be associated with high-or low-density regions.Vertical channels-2 km wide extending 6-8 km,of intermediate resistivity(150-300 ohmm),appear in three resistivity profiles analyzed.In one case,it coincides with a low-density region(<2.57 g/cm3)and in the others appear associated with fractured regions pertaining to the resurgent activity.We find that the magma chamber is not directly located under Los Humeros caldera;it is rather displaced -7 km to the north of the location of the caldera.Comparison with two shallow resistivity profiles shows that geothermal fluids induce propylitic alterations in high-and low-density regions.展开更多
An analytical methodology for reservoir characterization was applied in the central and southwestern zones of Los Humeros geothermal field(LHGF). This study involves analysis of temperature, pressure,enthalpy and perm...An analytical methodology for reservoir characterization was applied in the central and southwestern zones of Los Humeros geothermal field(LHGF). This study involves analysis of temperature, pressure,enthalpy and permeability in wells and their distribution along the area. The wells located in the central western side of the geothermal field are productive, whereas those located at the central-eastern side are non-productive. Through temperature profiles, determined at steady state in the analyzed wells, it was observed that at bottom conditions(approximately 2300 m depth), temperatures vary between 280 and360℃. The temperatures are higher at the eastern side of central zone of LHGF. A review of transient pressure tests, laboratory measurements of core samples, and correlation of circulation losses during drilling suggest that permeability of the formation is low. The enthalpy behavior in productive wells shows a tendency of increase in the steam fraction. It was found that productivity behavior has inverse relation with permeability of rock formation. Further, it is observed that an imbalance exists between exploitation and recharge. It is concluded from the results that the wells located at central-eastern area have low permeability and high temperature, which indicates possibility of heat storage.展开更多
基金supported by IIMAS and Instituto de Geofísica,UNAMwe acknowledge material support from both institutions.
文摘Los Humeros is a Pleistocene caldera in the eastern portion of the Trans Mexican Volcanic Belt,exploited for geothermal resources for over five decades,presently providing over 90 MWe.We model the gravity field,obtaining 3D density models from high-resolution(220 m)satellite-derived gravity data and compare these models with geological and magneto-telluric descriptions detailed elsewhere.An additional comparison with a geological E-W section indicates that the most voluminous caldera formations coincide with a low-density region extending from the surface to below 6 km bsl that is likely associated with the caldera activity.Interpretation of three additional density crosssections leads us to infer that the magmatic system feeding Los Humeros also has a component surfacing 12 km north of the center of the caldera,a result that is first disclosed here.Comparison of the density distributions with three corresponding electrical resistivity profiles obtained elsewhere from magnetotelluric soundings shows that low-resistivity regions prevail above 1 km asl where high-density pockets alternate with low-density regions.High-resistivity regions can be associated with high-or low-density regions.Vertical channels-2 km wide extending 6-8 km,of intermediate resistivity(150-300 ohmm),appear in three resistivity profiles analyzed.In one case,it coincides with a low-density region(<2.57 g/cm3)and in the others appear associated with fractured regions pertaining to the resurgent activity.We find that the magma chamber is not directly located under Los Humeros caldera;it is rather displaced -7 km to the north of the location of the caldera.Comparison with two shallow resistivity profiles shows that geothermal fluids induce propylitic alterations in high-and low-density regions.
基金support to the Instituto Nacional de Electricidad y Energias Limpias (INEEL)
文摘An analytical methodology for reservoir characterization was applied in the central and southwestern zones of Los Humeros geothermal field(LHGF). This study involves analysis of temperature, pressure,enthalpy and permeability in wells and their distribution along the area. The wells located in the central western side of the geothermal field are productive, whereas those located at the central-eastern side are non-productive. Through temperature profiles, determined at steady state in the analyzed wells, it was observed that at bottom conditions(approximately 2300 m depth), temperatures vary between 280 and360℃. The temperatures are higher at the eastern side of central zone of LHGF. A review of transient pressure tests, laboratory measurements of core samples, and correlation of circulation losses during drilling suggest that permeability of the formation is low. The enthalpy behavior in productive wells shows a tendency of increase in the steam fraction. It was found that productivity behavior has inverse relation with permeability of rock formation. Further, it is observed that an imbalance exists between exploitation and recharge. It is concluded from the results that the wells located at central-eastern area have low permeability and high temperature, which indicates possibility of heat storage.
