The drill bit is a tool used to break rocks to form well holes in oil drilling, and its working performance will directly affect the drilling quality, drilling efficiency and drilling cost.
Classification of drill bits
According to the drilling method, oil drill bits can be divided into four types: drag drill bit, roller cone drill bit, diamond drill bit and PDC drill bit; According to the function, it is divided into full-scale drilling bits, core drilling bits and special process bits (such as reaming bits, directional deflection bits, etc.).
Today I will show you about diamond drill bits
Diamond drill bit refers to a drill bit that breaks rocks by diamond particles embedded in the bit matrix. Diamond is the material with the highest hardness and the highest wear resistance among the materials known to mankind. Therefore, diamond drill bits are used in hard and highly abrasive formations to obtain relatively high drill footage. Although diamond is relatively expensive, diamond drill bits wear less, and a single drill bit has a high footage, so it still has strong competitiveness in today's oil drilling. At present, diamond bits are widely used in ordinary rotary drilling, turbo drilling and coring operations, among which thermally stable polycrystalline diamond teeth (TSP) are especially widely used.
Structural characteristics of diamond drill bits
he diamond drill bit is a one-piece drill bit, and the whole drill bit has no moving parts, mainly including the drill body, the crown, the hydraulic structure (including the water eye or nozzle, the water groove, also known as the flow channel, and the chip flute), the gauge, the cutting edge (tooth) five Part, the crown of the diamond drill bit is the working part of the drill bit cutting rock, its surface (working surface) is inlaid with diamond material cutting teeth, and a hydraulic structure is arranged, and its side is the gage part (inlaid with gage teeth). The bit body is connected and is made of tungsten carbide matrix or steel material. The drill bit body is a steel material body, the upper part is connected with the drill string by a screw thread, and the lower part is connected with the crown matrix (the steel crown is integrated with the drill bit body).
How Diamond drill Bits Work?
When the diamond bit drills, multiple diamonds on the surface of the bit act on the rock at the same time. The role of diamond in crushing rocks shows different characteristics in rocks of different properties. In plastic formations (or formations in which the rock is plastic under stress), diamonds enter the formation under the action of bit pressure and cause the rock in front of it to be broken or plastically flowed under the action of the drill bit torque. The rock breaking process is similar to "plow ground" process, so it is called "ploughing".
When drilling in brittle formations, the main effect of diamond crushing rock is "crushing". The stress generated under the action of drill pressure and torque can make the rock under the blade crack along the maximum shear stress plane. A fractured groove is formed in the rear part. In this case, the volume of rock crushing is much larger than that of diamonds after ingestion. Rock crushing has the nature of volume crushing, and the rock breaking efficiency is high.
In hard formations (such as chert, siliceous dolomite, etc.), the impregnated diamond bit with fine-grained diamond embedded in the matrix is generally used for drilling, and the rock-breaking process is similar to the grinding of the grinding wheel. Each diamond contained on the drill bit is a small blade tooth, and the drill bit can be regarded as a tool with countless blades. When the drill bit drills into the rock, the sharp diamond teeth exposed on the drill bit break the rock by micro-cutting, marking and other methods. Grinding rock breaking belongs to surface crushing, and the rock breaking efficiency is low.
How to use diamond drill bits correctly?
Diamond drill bits are suitable for drilling medium to hard, abrasive formations and turbo drilling, deep and ultra-deep well drilling and coring operations. Before using the diamond drill bit, the bottom of the well should be fished clean to ensure that there are no metal falling objects. When the drill bit is just lowered to the bottom of the well, it must first run in with a small drilling pressure and a low speed. Then use relatively low bit pressure (compared with roller cone bit), high speed and large displacement drilling. Eye scratching should be avoided as much as possible. If reaming is necessary, low drill pressure and low speed should be used, and the operation should be uniform to prevent diamond fragmentation and excessive wear on the gauge part of the drill bit.