Study On The Basic Characteristics Of Ruili Geothermal Field In Yunnan Province And Its Cause Analysis

Ruili geothermal field is located in3kilometers southwest of Ruili City of Yunnan province, and belong to the geothermal system of fracture of deep cycle and magmatic heat sources. In the geothermal field, the tectonic movement is very active, the fault structure development, metamorphose and magma activity are frequent. Now in the geothermal field hydrothermal activity is unusually strong, so there are huge potential for tourism, power generation, medical development. So it is of great significance for us to understand the basic characteristics and Atsuta genetic model of the geothermal field for the development, utilization and integrated management of geothermal fields.By collecting and sorting predecessors’ research data, combining with the field reconnaissance, this paper systematic discusses the geological conditions, terrestrial heat flow and characteristics of the geothermal field,geothermal reservoir fluid chemistry characteristics and geothermal field heat sources, thermal passage, hot reservoirs of geothermal field etc, the geothermal field’s formation mechanism was finally concluded and the conceptual mode was established. The main conclusions are as follows:(1)There are medium-low temperature geothermal resources in the study area, heat sources are mainly the uncondensed magma in the upper mantle. The fault structure development not only controls the geothermal field but also provides a favorable channel for the geothermal fluid migration. Geothermal field’s vertical structure layer is divided into four, these include two core geothermal reservoirs of shallow (N2m) and deep (T3n) and two water and heat in insulation cap rocks with heat proof of upper(Q) and lower (N1n). The shallow is lyriform thermal reservoir and the deep is layered thermal reservoir.(2)The average geothermal gradient of hydrothermal is mostly>5℃/100m. Take Border Inspection Station and Nongen as the center, the vertical borehole temperature curve has warming, warming-cooling, warming cooling transform three types. Fault geothermal field’s center is mostly of warming type. (3)Shallow, deep’s thermal fluid chemistry type is mostly HC03-～Na+. Shallow thermal fluid’s migration mode is hybrid type, the deep thermal fluid’s migration mode is deep fluid type. Isotope test results shows that precipitation is the main source of geothermal water replenishment. S stable isotopes are enriched in hot water which indicating that geothermal field’s hydrothermal is associated with the recent magma activity.(4)Geothermal field’s genetic model can be summarized as atmospheric precipitation goes through faults and fractures and infiltrate to the deep infiltration, then horizontal movement into the aquifer (group). Deep groundwater is mothballed to the underground, heated magma chamber and do water-rock interaction with surrounding rock. Groundwater temperature constantly rise, forming a deep geothermal reservoir. Shallow aquifer(group)’s groundwater conduction heating through the rock mainly, and fault water-transmit and heat conduction rupture makes hot hydrothermal upwelling deep into the shallow, mixed with cold groundwater, and forming Ruili meddle-low temperature geothermal field.