Characteristics And Genesis Of Geothermal Water In The Minle Basin

As a sustainable clean energy,geothermal energy is an important strategic resource.The development of geothermal energy plays a vital role in alleviating environmental problems.In recent years,geological prospecting units have successively discovered some commercially valuable hot springs and geothermal water in the Hexi Corridor of Gansu Province,and have conducted exploration and development in areas where conditions permit,demonstrating good prospects for exploration.The Hexi Corridor Basin has developed faults and folds.It is a structural region that has been strongly active since the Quaternary.Its unique geothermal geological conditions have led to the diverse and uneven distribution of geothermal water in different geological structural units.The understanding of the main controlling factors is still weak,which restricts further effective exploration and development.This paper collects geothermal water samples and drill core samples from three geothermal wells in the Minle Basin,as well as logging data.Based on the comprehensive study of the regional geological background,comprehensive technical methods and means such as sampling and testing,geophysical interpretation,mathematical calculations,etc.,Conducted research on the characteristics and genesis of geothermal water resources in the Minle Basin,and obtained the following main understandings:(1)Obtain the fine section of the Minle Basin through drilling and logging data:the Late Ordovician granite body from bottom to top,and the Paleogene a set of complex sandstone,siltstone,fine sandstone,and unconformity contact with the underlying granite body,The thickness is 390 meters;the Neogene is mainly composed of mudstone,sandy mudstone,conglomerate mudstone,and siltstone,with a thickness of 1154m;the Quaternary conglomerate,sandy gravel,with a thickness of640 meters.Among them,the Neogene Shulehe Group sandstone,sandy mudstone and argillaceous sandstone are the geothermal water caprocks,and the Paleogene Baiyanghe Formation sandstone and basement granite weathering crust are the main thermal reservoirs.The reservoir temperature is 104?.The buried depth is about1788-2188m,and the heat storage thickness is about 280m.(2)The Minle Basin is a sedimentary basin-type medium-low temperature geothermal water,the hydrochemical type is Cl^--SO₄^2--Na⁺,the content of Na⁺,SO₄^2-,and Cl^-ions is high,and HCO₃^-and Mg²⁺ions are low;Divided into metasilicate,lithium,strontium and borate.The chemical composition of water is mainly controlled by evaporation and concentration,and the main ion composition is affected by the action of carbonate,silicate and sulfate minerals.(3)The age of the geothermal water in the Minle Basin is 29.31±2.72ka.The main source of recharge is the atmospheric precipitation in the Qilian Mountains,and the recharge elevation is about 3446m-5113m.The heat source may be the heat generated by the warming of the earth's heat flow and the radioactive decay of the granite body.