Geothermal drilling characteristics of geothermal drilling the main oil and gas well drilling technology for reference, because the heat reservoir rock geological conditions, such as lithology, buried depth and output fluid property is different, compared with more demanding conditions of oil and gas drilling, geothermal drilling, but also for geothermal well characteristic of the high temperature and large diameter to new technology and new equipment improvement and development.
Compared with oil and gas drilling, geothermal drilling has the following characteristics:
High temperature, great variation in buried depth.
The rock is hard, abrasive and high in-situ stress heat storage rocks are mostly volcanic and metamorphic rocks. Compared with the deposition rock of oil and gas wells, the rock is hard, abrasive and high in-situ stress, and the stratum is broken and often unstable.
The crack height is developed, and even centimeter-grade cracks exist.
Formation pressure is low and leakage is serious.
The formation often contains corrosive fluid, which is corrosive to drilling string, casing, etc.
This requires the production of expensive titanium alloy bushing and the development of special cement.
The geothermal well has a large diameter, many casing procedures and a large amount of cement.
Drilling a geothermal well is similar to drilling oil, gas and well. In order to overcome the special difficulties in drilling, drilling methods, flushing media, drilling tools, casing head structure, wellhead device and other appropriate technical measures should be adopted.
The drill pipe and drill collar with high-temperature resistance, corrosion resistance, low coefficient of thermal expansion and high strength should be used in the drill pipe and drill collar.