Sustainable Development And Utilization Of Thermal Groundwater Resources In The Geothermal Reservoir Of The Wumishan Group In Tianjin

Wumishan geothermal reservoir of the Jixian system widely distributes in Tianjin and is the most important reservoir of geothermal development and utilization. The development and utilization of geothermal resources in Tianjin has began since the 1980's in the 20th centuries. By the end of 2005, the yield is 891.8×10~4 m~3/a. Because of more than 20 years of large-scale and continuous utilization, the water level keeps on significantly descending. Since 1997, the average descension of water level is 6-10 m/a, the biggest is 13 m/a. The total water level descends to about 120 m below the land surface in 20 years, and forms a district drpression cone. Therefore it is urgent to study the sustainable development and utilization of thermal groundwater in the Jixian system reservoir.The Jixian system reservoir imbeds deep;the geological structure is very complicated. This paper accurately explores the structure characteristics and the space contribution regulation, the formation mechanism of underground heat of reservoir which concentrates on the area 2200 km~2. Through studying the data of more than 70 wells, this paper further discusses the space exhibition, property and movable history of main fault.This paper studies the characteristics of geological structure, the relation of reservoir structure and capacity of store through theoretical analysis of structure stress. For the first time to semi-quantitatively and quantitatively analyze the regulation of capacity of store and karst growth, semi-quantitatively analyze the mechanism of geothermal formation, namely the main characteristics of the heat conduction this area, but heat convection is prominent in deep and great fault, for example Cangdong fault, the joint of Baitangkou fault and Haihe fault. This paper analyzes the main elements of controlling reservoir temperature and the relation of reservoir temperature and reservoir structure.This paper studies Jixian system reservoir dynamic field and the evolutive regulation using reservoir engineer, hydrogeology, geochemistry and points out that the geothermal development must stick to sustainable way, the reinjection development is only solution to realize the sustainable development and utilization in Tianjin area. Especially it is important for deeply buried and bad supplied Jixian system reservoir. This research carries detailed summary to geothermal reinjection in Tianjin area.This paper uses TOUGH2 which is general-purpose numerical simulation program for multi-phase fluid and heat flow in porous and fractured media to stimulate the Jixian system reservoir widely laying in concentrating production zone (2200 km~2) in Tianjin. Study the evolutive regulation of dynamic field and temperature field under the different production situation. Putting forward the model of sustainable development of geothermal water should be one well for production and one for reinjection. The amount of production is the equal to reinjection of fitting water quality, or just using heat not using water. This paper the first attempts to quantitatively study regeneration of middle-low temperature geothermal resourcesand puts forward not to engender negative influence to development and utilization of Jixian reservoir according present using mode that the reinjection temperature is about 3O°C.It is best project to place 12 reinjection wells of reinjection of 622xlO4 mVa, the yield is 1050xl04 m3/a. in the concentrated production areas and north-east and south of concentration production areas. This paper the first simulates the change regulation of temperature field using different reinjection temperature (30°C, 9°C).This paper studies the present situation of development of Jixian system reservoir in Tiajin, and puts forward to the geothermal resources synthetical utilization project according to the current technique and economic level of this area combining the characteristics of Jixian system reservoir.The results of this research have not only a certain instruction to the further development and utilization of geothermal resources in Tianjin but also a great help to perambulation and development of geothermal resources in other areas.