Importance of Drill Bit in Drilling Operations
The drill bit is one of the core tools of drilling operations. Through continuous innovation of drill bit materials, design and manufacturing technologies, the development of high-efficiency rock-breaking and long-life drill bits can shorten the tripping operation time and drilling cycle, greatly improve operating efficiency and reduce operating costs.
Types of PDC Drill Bit and Their Characteristics
The selection of PDC bit is mainly determined according to the construction environment and the needs of drilling construction. Different bits have different characteristics. When drilling, the bit should be selected reasonably according to the change of lithology. In relatively hard rock formations, it is generally advisable to use thicker diamond drill bits. According to the drillability, abrasiveness and integrity of the rock, diamond drill bits with different matrix hardness and particle size can be selected to obtain better results. The drill bit can achieve higher drilling efficiency and bit service life. If the drill bit is not suitable for the formation conditions, it will cause problems such as drill bit slippage, increased wear, low drilling efficiency and short life of the drill bit.
Advantages and Applications of PDC Drill Bit
1) The entire bit body of the steel body PDC bit is made of medium carbon steel and processed by mechanical manufacturing technology. Drill holes on the working surface of the drill bit, and fasten the PDC cutting teeth to the crown of the drill bit by means of a press-fit tight fit. The crown of the drill bit is treated with surface hardening process (spraying tungsten carbide wear-resistant layer, carburizing, etc.) to enhance its erosion resistance. The main advantage of this kind of drill is that the manufacturing process is simple; the disadvantage is that the drill body is not resistant to erosion.
2) The matrix type PDC drill bit is a kind of cutting drill bit in which the diamond compact is welded to the bit matrix by brazing. The matrix bit is sintered with tungsten carbide powder, brazed on the tungsten carbide matrix with artificial polycrystalline diamond composite sheet, and uses natural diamond gauge. The tungsten carbide matrix has high hardness and erosion resistance, so the matrix PDC bit has a long service life and high footage, and is currently widely used.
The PDC bit breaks the rock by cutting. The self-sharpening cutting teeth can easily cut into the formation under the action of drilling pressure, and move forward to shear the rock under the action of torque. Multiple PDC cutting teeth work at the same time, there are many free surfaces of the rock at the bottom of the well, and the rock is easily broken under the action of shearing, so the rock breaking efficiency is high and the drilling speed is fast.
Correct use of PDC drill bit:
- PDC bit works best in large homogeneous soft to medium hard formations. It is not suitable for drilling gravel layers and soft-hard formations.
- It adopts low drill pressure, high speed and large displacement for drilling, and the drill bit has good effect.
- Before the drill bit goes into the well, the bottom of the well should be cleaned to ensure that there is no metal falling.
- When the drill bit is just going down the well, it should run with small drilling pressure and low speed, and resume normal drilling after the bottom of the well is formed.
- The PDC drill bit is an integral drill bit without any moving parts, suitable for high-speed turbo drilling.
When applied, the PDC bit can realize high-speed drilling in soft formations, and can also be used for well deviation and azimuth control, and can be applied to drilling in directional wells, horizontal wells, and cluster wells. It can also cooperate with turbine and screw to realize compound drilling.