Geographical location

 

    Yangbajing, is located in the town of Yangbajing, Tibet City, Lhasa The territory of 91.8 kilometers northwest of Damxung county. The thermal field is flat, 4300 meters above sea level, North and south sides of the mountain are at an altitude of 5500 to 6000 meters above, the development of modern mountain glaciers, the Zangbo River flows through the thermal field, the annual average temperature of 5 degrees, the annual average temperature of 2.5 degrees, with an average of 60000000000 years of atmospheric pressure. In the vicinity of the economy dominated by agriculture and animal husbandry, with few. Tibet Nepal, two highways respectively from the north and East by thermal field, traffic is convenient.

 

    Geological background

 

    Geothermal field located in the center of YBJ fault basin near a little south of the mountain Nyainqentanglha. The south side of geothermal field is Mount Kailash volcanic magmatic arc, the north is metamorphic uplift mountain.

 

    YBJ geothermal reservoir is divided into two closely parts, shallow layer and deep layer, to clear the two different parts of a hydrothermal system. The shallow layer geothermal reservoir is Quaternary pore type thermal storage, very shallow depth, the distribution range of about 14.8 square kilometers. Southern low temperature, high temperature the north. Hot fluid has a north west - south east direction lateral recharge characteristics. Geothermal reservoir depth is between 180 ~ 280m. The lithology concludes the Quaternary Alluvial sand and gravel, moraine gravel layer, on top of bedrock composed of granite weathering crust. Deep geothermal reservoir located in Geothermal field North 3630m elevation or less. The effective area of deep geothermal reservoir is about 3.8 square kilometers, the fluid reservoir and migration are strictly controlled by faults in this area. Fluid mainly occurs in fractured and tectonic fissures space, and as a reservoir migration space, in the form of high-temperature thermal energy storage with a presence in some depth and range. Gum is a typical rock base structure fractured geothermal reservoir.

 

    The development history of the geothermal power station

 

    September 1977, moisture vapor resources of shallow geothermal reservoir are used to build an experimental geothermal power plants. In 1993, in the northern geothermal field, ZK4002 well is drilled, of which depth is 2006.8 meters, with the temperature at 1,500 meters up to 262.3℃. In 1995, it has been drilled ZK4001 well, 1459 m depth, wellhead temperature reaches 200 ℃, and the capacity of steam flow reaches 302 t/h. Until the end of December 2004, installed capacity remained at 25.18 MW, annual generation capacity is 100 X 103 MW ? h. Except for geothermal power generation but also for vegetable greenhouse, it gets good results.

 

    The ground power system

 

    The YBJ’s first power generation units is designed by Southwest Electric Power Design Institute. the capacity is 1000 kW. Turbine is transformed from the obsolete equipment, that is  Neijiang power plant’s 2500kW units. In October 1977, a successful trial operation, which uses a single-stage expansion Thermal System. If the ground water is fed into a sealed container to reduce pressure, expansion, based on the relationship between boiling point of water and pressure, we can make the geothermal water that don’t have too high temperature geothermal water boil into steam by reduction in pressure. Due to the evaporation of water down fast, which is a process by flash evaporation; the same time, when the ground water evaporation to produce steam, the rapid expansion of its volume, so that the container is called "expansion" or "flasher" . This method for producing steam to generate electricity expansion is called geothermal power generation. This is one of the main geothermal field water power, and this mode is divided into single-stage and two-stage (or multi-stages)expansion method system. The system expansion law principle is: the middle-temperature geothermal steam and water mixtures from the geothermal wells were firstly sent to the expansion device for reducing pressure, expansion (called flash evaporation), in order to produce parts of steam. And the steam go through the separator to remove impurities (10μm and above), and then lead to a conventional steam turbine to generate electricity.