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Basic Knowledge
2.2 Drilling classification
  • Detailed description

According to different requirements and purpose, well drilling can be divided into exploration well and development well. 
Exploration well—drilling this kind well to get geological conditions, underground strata oil and gas resources distribution and the corresponding property. Exploration wells can be divided into the following several kinds:①Geological shallow wells which is drilled to cope with the ground geological and geophysical work, and in order to understand the regional geological structure, strata profile and the local structure.②Geological exploration wells which is drilled in order to understand the era, lithology, thickness and source reservoir seal assemblage of the strata,and for the purpose of offering all kinds of parameters for geophysical interpretation.③Preliminary exploratory well which is drilled for the purpose of finding reservoirs in the favorable structural combed through detail shooting and comprehensive geological research.④Detail exploration well which is drilled for the purpose of  the area and reserves of oil gas, understanding the hydrocarbon reservoir structure change and capacity in the found oil and gas construction.⑤Date well which is drilled for the purpose of preparing oil and gas development plan, or getting first-hand information data for some research project in the development process.
Development well—it is drilled for the purpose of development, and providing its proven underground oil and gas channel, or using all sorts of measures to quarry oil and gas. Development well can be divided into the following several kinds①oil gas well which is drilled by large-medium size rig for the purpose of oil and gas development and it is also be called production well.②injection well which is drilled in order to develop oil gas field reasonable and enhance recovery and develop speed. And it is used to inject gas and water to oil-gas field and to supplement and reasonable use the formation energy t.③observation well which is drilled in the developed oil gas field to institute the underground constitution changes in the development process.
According to the rock broken way and the tools type used drilling methods can be divided into the following kinds.
Cable-system drill—first, transfer the bit with steel wire rope to bottom, and then use power machine driving walking beam to move up and down, and which drive the wire rope and drill bits producing impact to break rock. It is also called percussion drill. (Picture 1) it is an old drilling method. Its advantage is saving time, costing small equipment simple and not pollute reservoir.  ①Broken rock, remove debris assignment is discontinuous②smaller bit power, lower rock fragmentation efficiency and drilling speed③cant control the pressure in the well④only used in drilling straight well In countries such as the USA there is still a certain amount of oil gas well is drilled with drilling method. Great majority oil wells in China's northern shaanxi yenan and salt wells in sichuan artesian well area are drilled with this method.

Picture 1 cable drilling diagram

Rotary drilling-- Use cutting or abrasive produced when bit rotating to break rock. It is the most common drilling method. (Picture 2) Characteristic:①Finish up the tasks of snubbing in or out drilling tools, transfer torque, providing drilling pressure on drilling bit and providing wash well liquid into the well channels etc.②Drill in a certain drilling pressure, improve the broken rock rate③break the rock, at the same time well debris at the bottom is cleared out.④enhancing drilling speed and efficiency. In 1901 the United States first used and Chinese begin to use in the 1930s.

Picture 2 rotary drilling diagram