1. How many meters can be called deep geothermal well depth?
      Deep or deep well drilling，refers to the drilling depth of more than 3000 meters，deep geothermal drilling is more than 3000 meters in the field of geothermal drilling.（Drilling rig ZG - 45， drilling as deep as 4500 m or so）
 
2. Shallow geothermal well drilling technology and several important problems in drilling.
      Note: this part is identical with the basic of shallow geothermal drilling，please see the shallow geothermal drilling.
 

3. Conventional well structure diagram

4. Some problems that should be paid attention to in geothermal well construction

1.Drilling efficiency
      On the subsurface fluid resources development，It often require safety suppling in the short time and reduce the cost. We should prolong the service life of drill bit，improve the drilling speed，shorten the drilling time，reduce the labor intensity. It involves the use of the drill bit，suppling technology research，According to the formation conditions and equipment conditions，We will carry out the different technology method.

2.The mud leakage during the construction process
      In the mud loss，a part of mud will access to the formation or total loss，resulted in cyclic interrupt，there will lead to many serious problem，for example，the blocking accident，Drilling efficiency drops，Formation collapse，mud boil and blowout and so on，It will bring more serious consequences if we only considering the cost， cannot use high-quality mud. Therefore，it should be atention that the judgment of the amount of mud loss，position，reasons，the consequences of mud loss and the solutions on mud loss.

3.The mud
      These problem should be paid attention，include the service life of the bit，the prevention of mud gelation and curing， slurry heat loss，the borehole cooling and boiling in well，we should develop a new method of heat-resistant mud and cooling circulating mud.

4.Cement grouting
      Fix the casing in the well with cement grout for leaky Stratum,this method is worthy of discussion, it is a key that how to judge the effect of cement grouting.It is urgent to develop cement with long time to maintain the consistency and no weakening at high temperature.

5.Prevention of groundwater pollution
      Because there are many fractures in the rock，Often the case of mud leakage in drilling water bearing stratum and well formation. In order to prevent the pollution of the aquifer, we must develop a flushing fluid without bentonite,and use  gas lift reverse circulation drilling technology as far as possible at the same time.

6.Directional well drilling
      For drilling the production wells and injection well in the same hole,directional drilling should be developed in the future. The key problem is the determination of orientation and tilt in hard rock with high temperaturea .

7.Physical detection
     Judgement of  location and property of the aquifer.How to develop geophysical logging equipment at high temperature .

8.Environmental protection
      The environmental problems caused by geothermal development are as follows:
      1) The diffusion of special stink, gas and particulate
      2) Noise
      3) Saline water diffusion
      4) Landscape changes
      5) Stratum subsidence
      6) Surface water and groundwater pollution