The Characteristics Of Geothermal Reservoir And Evaluation Of Resources For The Guantao Formation In Cangzhou Region Of Huanghua Depression

Geothermal resources are new green renewable clean energy source.Compared with wind and solar energy,they are not affected by external factors such as seasonal,climate,diurnal changes.Geothermal resources are competitive new energy source due to their sizable reserves,wide distribution,and easy accessibility.Geothermal energy has become an important subject of energy research in the world today.The utilization of geothermal energy in house heating,bathing and other fields has become an effective way to improve the urban atmospheric environment and reduce greenhouse gas emissions.Geothermal resources are abundant and widely distributed in the Cangzhou area.Regional exploration data reveal that the thermal storage of the Neogene Guantao Formation has high large porosity and permeability and contains rich geothermal resources.However,quantitative evaluation of the amount of geothermal resources in the Guantao Formation remains debated.It is therefore imperative to characterize the thermal storage and quantitatively evaluate the geothermal resources of the Guantao Formation,which would provide geological data for the rational development and sustainable use of geothermal resources and guide the establishment of mining properties,scientific planning,management and effective protection of the geothermal resources.The target of this paper is the Guantao Formation in Cangzhou area of Huanghua depression.The study area is located in the southern section of the Huanghua Depression?Grade III?which belongs to the North China depression?Grade II?in the North China platform?Grade I?.It is sandwiched between the Cangxian anteklise and the Chengning anteklise.The tectonic unit is bounded by the Yangerzhuang fault in the east and the Cangdong fault in the west and can be subdivided into 7 IV tectonic units,namely the Cangdong sag,the Qijiawu uplift,the Kongdian uplift,the Qikou sag,the Nanpi sag,the Xuli uplift,and the Yanshan sag.Based on detailed compilation of previous data and field investigation,we performed bulk hydrochemical,isotopic analyses,and radiometric ¹⁴C dating to characterize the nature,source and timing of geothermal fluids.Hydrogen and oxygen isotope analyses reveal that the geothermal fluids in study area were mainly from the supply of meteoric water.The age of geothermal fluids was determined by ¹⁴C dating to be27–32 ka.Further,the amount of bulk and recoverable resources was evaluated using the thermal storage method and recoverable coefficient method.The results show that the explored amount of geothermal resources of the Guantao Formation in the study area is 7651.66×10¹⁶J,with the recoverable resources reaching to 1912.91×10¹⁶J.The total storage of the geothermal fluids is 1781.59×10⁸m3,and about 17.81×10⁸m3among them is recoverable,which amounts to the recoverable fluids geothermal resource of 29.93×10¹⁶J and the total capacity of recoverable fluids geothermal water resources of 293.69 MW.The enrichment of geothermal resources reaches to the grade of large geothermal field in the study area.Evaluation of the water quality based on bulk geochemical analyses suggests that the geothermal fluid from the Guantao Formation in the study area does not meet the standards for drinking water,drinking natural mineral water,fishery water and agricultural irrigation water,but it is suitable for physiotherapy hot spring spa.In addition,the geothermal fluid in the study area is corrosive,easily fouling and blistering,which should be particularly taken into consideration during the exploration and utilization.Finally,we briefly discuss the formation mechanism of geothermal resources in the study area and provide some suggestions for reasonable development and protection of geothermal resources.