Geothermal occurrence analysis of Dongying Formation in Tanggu area of Tianjin

Based on introducing geological structure of Tanggu area，the authors analyzed the sedimentary envi- ronment of Paleogene Dongying Formation，and further analyzed its geothermal occurrence． The studied area spans two grade Ⅳ tectonic units which are Beitang depression and Banqiao depression． The studied area is mainly located in the Tanggu nose- like structure which is the secondary structure of Beitang depression． Its ex- istence affects the sedimentary distribution of the part strata of Paleogene． The depositions of Dongying Ⅲ (SQEd 3 ) and DongyingⅡ (SQEd 2 ) are mainly delta front facies and lake sand bars which are propitious to the geothermal fluid enrichment． The favorable enrichment region of geothermal fluid is located in south Hetou- Tanggu． Most of DongyingⅠ (SQEd 1 ) changes into swamp plain deposition， only the northeast part of this area is the distributary riverway facies with developed sand layers． There is the favorable enrichment region of geo- thermal fluid． The hydraulic connection is weak among the geothermal reservoirs of Dongying Formation and its overlying Guantao and Minghuazhen formations． The underlying Shahejie Formation geothermal reservoir pro- vides a steady stream of fluid supply and ground pressure protection for Dongying Formation geothermal reser- voir．