Research Progress of Deep Geothermal Exploration in Dongli Lake Area, Tianjin, North China

Chinese government put high emphasis on geothermal development and utilization. In order to enlarge the amount of exploitable geothermal resources, improve the status of geothermal resources in energy structure, and to meet the demand of clean heating in the north area, China Geological Survey are launching deep geothermal exploration program in the recent years and focusing on new reservoir exploration in the depth of 3 to 6 km underground. Geothermal exploration in Dongli Lake area in Tianjin city is among this program. Through regional geological research and analysis, two types of reservoirs were confirmed existing in the study area, such as porous reservoir and karst reservoir. Porous reservoir has two sub-reservoirs, one is in Minghuazhen formation and the other in Guantao formation. Both of them belong to Neogene era. Karst reservoir has three sub-reservoirs in Ordovician, Cambrian and Jixian systems. Among these reservoirs, section 4 and 3 in Wumishan formation of Jixian system is the main development reservoir in current period. Induced seismic and high power time-frequency electromagnetic methods were used in deep geophysical detection and got good results in description of the underground cap rocks, reservoirs and faults within 5 to 6 km. Furthermore, 3D geological structure model was built with geostatistical method for resources assessment use. Based on the preliminary work above, deep drilling work was implemented and finally section 2 in Wumishan formation of Jixian system was found in the depth of 3715m. Fortunately, reservoir production test shows that this new reservoir has enormous resources prospect. This research is of good significance not only in support of local geothermal development, but also in demonstration of geothermal exploration in sedimentary basins.