PDC drill bits play an indispensable role in the fields of coal, oil and gas mining and geological exploration, and their performance directly determines the drilling efficiency and cost. However, in the process of actual application, PDC drill bits often have various problems, resulting in their inability to work properly, so-called failure. These failures seriously affect the drilling progress, increase the economic cost, and may even lead to safety hazards. In order to better demonstrate the superior performance of PDC drill bits and improve drilling efficiency, we need to understand the failure forms, and avoid these failure forms to achieve the best performance of PDC drill bits, next we will learn what are the failure forms of PDC drill bits.

(1) Cutting tooth wear

The wear of cutting teeth is mainly concentrated on the cutting teeth at the top of the crown of the PDC drill bit, and there are two forms of wear: abrasive wear and erosion wear. In the initial cutting period, the drill bit slowly cuts into the rock under high speed rotation and certain drilling pressure, and the cutting teeth are more subject to the impact force at this stage, and then the cutting teeth gradually enter the stable wear stage. When the diamond layer edge is worn, the contact between the cutting teeth and the rock changes from line contact to surface contact. This makes the friction between the cutting teeth and the rock increase, resulting in an increase in cutting resistance, and this process is mainly dominated by the grinding effect.

During the drilling process of PDC drill bit, the drilling fluid flushes the bottom of the well at a very high speed through the water hole of the drill bit, assisting the cutting teeth to complete the rock breaking and rock clearing. When the drilling fluid reaches the bottom of the well, it carries many small rock chips, forming a solid-liquid two-phase fluid, in which the small rock chips play the role of abrasive, eroding the cutting teeth at a certain speed and angle, accelerating the loss of cutting teeth.

(2) Fracture of cutting teeth

As the cutting teeth on the outside of the largest diameter of the crown of the PDC drill bit directly contact the rock during the drilling process and are subjected to the largest impact force, the fracture of the cutting teeth usually occurs in this position. The fracture of a cutting tooth will cause vibration of the drill bit due to the uneven force on the remaining cutting teeth, which seriously affects the drilling efficiency and service life. Generally divided into impact spalling and chipping.

(3) Cutting teeth falling off

The former is mainly due to the alternation of heat and cold in the PDC drill bit during the drilling process, which is caused by the big difference between the thermal expansion coefficient of the diamond layer and the tungsten carbide substrate, or the quality problem of the diamond composite piece; the latter is generally caused by the unreasonable welding or the loss of support due to excessive wear of the drill bit body. The shedding of cutting teeth has a great impact on the later drilling, so the occurrence of this situation should be eliminated.

(4) Drill bit mud pack

In some viscous formations or poor drilling fluid performance, rock chips are easy to accumulate and adhere on the surface of the drill bit. When the PDC drill bit is encrusted with mud, the cutting teeth cannot fully contact with the rock, resulting in lower breaking efficiency. Moreover, mud pack also affects the cooling effect of the drill bit, increasing the risk of wear and damage to the drill bit. When the mud pack phenomenon is serious, it may lead to jamming or burning of the drill.

(5) Bit body damage

In the complex downhole environment, such as strong vibration, impact load and corrosion and other factors, the drill bit body may be structurally damaged, and unreasonable structural design will also lead to excessive wear of the drill bit body, which will seriously affect the normal use and life of the drill bit.

Therefore, to prevent the failure of PDC drill bit, preventive measures can be taken from the aspects of material formula, structure design and use method. On the one hand, we can change the external conditions and adjust the drilling parameters to keep the PDC drill bit drilling smoothly; on the other hand, we can improve the quality of the cutting teeth from the quality and structure shape of the PDC cutting teeth themselves, and choose more wear-resistant and impact-resistant cutting teeth and bit body.

Select cutting teeth and bit body with stronger wear resistance and impact resistance, such as diamond composite piece of BN(CHINA) Technology, to improve the overall performance of the drill bit.

The diamond composites produced by BN(CHINA) Technology have fusion growth between diamond particles, forming close D-D bonds, high bonding strength, close bonding of diamond material interfaces, no stress and no defects, comparable to foreign products, as shown in the following figure for comparison of microstructures.

The large-scale batch synthesis equipment guarantees the consistency and stability of product quality as well as delivery capability. At the same time, we have a wide range of products, which can satisfy the application in different fields, and have the performance of high-grade products but have the price of mid-range products.