About Author:Guodong “David” Zhan, Ph.D.

David Zhan is a Senior Consultant and Head of the Advanced Drilling Tools Team at the Saudi Aramco EXPEC Advanced Research Center.
He has a strong background in materials engineering and drill/cutting elements, especially in the development of new materials for PDC Cutter, catalyst-free PDC material technology, wear resistance and thermal stability improvement.

Flat PDC Cutter, with its unique flat geometry and excellent cutting performance, has become an indispensable core component in modern high-performance drill bits. It not only carries the important task of improving the rate of penetration (ROP) and extending the life of the drill bit, but also is a powerful weapon to adapt to complex formations and overcome severe drilling challenges. However, the models on the market (such as 1313, 1613, 1308, 1916, etc.), as well as the complex principles of material science and engineering mechanics behind them, often make users face a lot of confusion when selecting and applying.

This article will conduct a comprehensive in-depth analysis from the technical principles of Flat PDC Cutter, detailed classification (covering various sizes and models), key performance indicators, to its selection strategy under different formations and operating conditions. My goal is to provide you with a professional guide that is both highly theoretical and practical, so that you can make the most informed decisions when facing the core technology of “Flat PDC Cutter”, so as to truly improve your drilling efficiency and economic benefits.

Flat PDC Cutter

A. Definition and composition

Flat PDC Cutter is the PDC compact with a flat cutting edge. You may think the name is a bit redundant, isn’t it all PDC Cutter? But this “Flat” is exactly what distinguishes it from traditional arc or alien Cutter. Its most intuitive feature is that the cutting surface is flat.

Its basic composition is actually similar to the PDC Cutter we are familiar with, mainly two layers: the outermost layer is the diamond layer (PDC), which is the main force of our cutting rock, hardness is very high. Below is a hard alloy substrate, which mainly provides support strength and toughness, so that the whole Cutter will not break everything. There is a bonding interface between the two layers. Don’t underestimate this interface. Its bonding strength directly determines the life and performance of Cutter. After all, if the diamond layer is separated from the substrate, it will be useless to be hard.

B. Core working principle

The core charm of Flat PDC Cutter lies in its “strong” and “adaptive”.

First of all, the cutting mechanism of the diamond layer is actually the commonality of PDC Cutter. Diamond is currently the hardest known material, in combination with cemented carbide under high pressure sintering, resulting in extremely high hardness and wear resistance. When the drill bit rotates and the Flat PDC Cutter touches the rock, the diamond layer can efficiently “scrape” or “shear” the rock with minimal wear, rather than the impact-based approach of traditional roller cone drills. This cutting method can maintain stable performance in the bottom hole environment of high temperature and high pressure, which is unmatched by many other materials.

In particular, I would like to emphasize one point, that is, “self-sharpness”. With drilling, the diamond grains at the front end of Cutter will gradually wear out, but because the diamond layer is composed of countless tiny diamond grains randomly distributed, after a certain degree of wear, new sharp diamond grains will be exposed and continue to provide cutting ability. This is like a never dull knife, so the life of the drill can be greatly extended. If the traditional Cutter is worn out, it is basically useless, but PDC Cutter can continuously provide effective cutting surface, which is the embodiment of its economy.

As the drill bit spins with these Cutters at high speed and pushes down, each Cutter makes an arc on the rock. Flat’s geometry allows it to generate more radial force when cutting, which I think is particularly effective for improving Rop (rate of penetration) and dealing with some hard formations. The cutting force is mainly the reaction force generated by the contact between the diamond layer and the rock. Under the complex working conditions of high temperature and high pressure at the bottom of the well, how to balance the cutting force, reduce heat generation and avoid premature failure of Cutter is a problem that we engineers have been thinking about and optimizing.

Types and Key Performance Indicators of Flat PDC Cutter

A. Geometric size and type classification

• 1308 PDC Cutter: 13mm diameter, the diamond layer is only 8mm thick. This model is usually used in scenes where the requirements for cutting force are not particularly high, but the drill bit is required to have good toughness. For example, in some brittle or complex bedding rock, thin diamond layer can provide better anti-cracking performance, to avoid premature failure.
• 1313 PDC Cutter: This model has a diameter of 13mm and a diamond layer thickness of 13mm. It not only ensures sufficient cutting area, but also takes into account the durability of the diamond layer. We usually apply it to medium hard formations, especially in some directional well operations that require precise control of the borehole, and its performance has been very stable.
• 1613 PDC Cutter: Compared with 1313, the diameter of 16mm makes its cutting ability stronger, but the thickness of the diamond layer remains at 13mm. In my opinion, this is designed to deal with harder or more abrasive formations. A larger diameter means that larger cuttings can be handled, but at the same time the torque requirements on the drill bit will increase accordingly.
• 1916 PDC Cutter: 19mm diameter, 16mm diamond layer thickness, which is definitely a typical representative of large-size cutting teeth. It has obvious advantages in dealing with large rock cuttings, especially for some well sections with high drilling speed requirements, or need to quickly penetrate soft but large rock interbedded formations. However, it also requires higher strength and chip removal capacity of the drill bit body.
• Other common sizes (such as 1908, etc.): Of course, there are 1908 such large diameter thin diamond layers, or some smaller models, they all have their own niche market. 1908, for example, may be used in the pursuit of high drilling speed but little change in rock hardness.

B. Deep analysis of key performance indicators

In addition to size, the performance of the PDC Cutter is the key.

• Wearability: This is definitely the lifeblood of the PDC Cutter. We enhance it by selecting the right diamond particle size, distribution and, crucially, sintering process. The finer the particles, the more uniform the distribution, the denser the sintering, the better the wear resistance. This is the most basic and core requirement.
• Impact toughness: The drill bit rotates at high speed underground and constantly hits the rock. It is impossible without toughness. This mainly depends on the bonding strength of the diamond layer and the cemented carbide substrate, as well as the interface design between the two. Good design can effectively disperse the impact load and prevent the diamond layer from peeling or cracking prematurely.
• Thermal stability: During the drilling process, the friction between the cutting teeth and the rock will generate a lot of heat. If the performance of the PDC layer drops sharply at high temperatures, it will not work. Therefore, the thermal stability of the PDC material itself is very important. Some new PDC materials do this very well, maintaining cutting performance at higher temperatures.
• Self-sharpening: This is a bit like the pencil sharpener we use, the cutting teeth stay sharp as they wear. When the ideal PDC Cutter wears, the diamond particles will fall off in a controlled way, exposing new sharp edges, thereby extending the life of the drill bit while maintaining a stable drilling rate. This requires a clever balance of the internal structure of the diamond layer and the wear mechanism.
• Bonding strength (diamond layer and substrate): I personally think this is the indicator that determines the reliability of PDC Cutter. No matter how well said in front, if the diamond layer and the substrate are not firmly combined, everything is empty talk. We optimize the sintering process and interface treatment technology to ensure a strong metallurgical bond between the two to prevent shear failure under complex working conditions.

Application Scenario and Selection Strategy of Flat PDC Cutter

In my opinion, the application and selection of Flat PDC Cutter is definitely a combination of art and science. Unlike some products, it can solve the problem across the board, but we need to consider it carefully according to the actual formation and working conditions.

A. Typical application formations and conditions

Years of practice have told me that the power of Flat PDC Cutter has its own merits in different strata:

• Soft formation: in the face of soft formation, we usually tend to choose large size, high self-sharpening Flat PDC Cutter. Large cutting area, high cutting efficiency, plus excellent self-sharpening. My experience is that in this formation, this type of PDC Cutter can effectively avoid mud packs and improve ROP (rate of penetration).
• Medium hard formation: This type of formation is the one we encounter most often. Those conventional models, such as 1313 and 1613, can show off here. They are characterized by wear resistance and toughness to do a very balanced, both to ensure a certain life, but not because too much emphasis on wear resistance and sacrifice toughness. In such formations, excessive pursuit of an extreme characteristic is often counterproductive.
• Hard formation/abrasive formation: to deal with this kind of formation, I have to choose those special PDC layers with high wear resistance, high toughness and strong thermal stability, combined with large-size PDC Cutter. The large size is to disperse stress and reduce single point wear; the special PDC layer is to cope with high temperature and high abrasion.
• Complex formation: My practice is to flexibly adjust the cutting tooth type and layout according to the formation changes. For example, when encountering sandstone with strong abrasive properties, I will consider configuring more cutting teeth with good wear resistance at the leading edge of the drill bit. If the interlayer changes frequently, it may be necessary to take into account the matching of cutting teeth with different hardness to achieve the best drilling performance. This is not a simple pile, but a deep understanding of the characteristics of the formation.
• Directional and horizontal wells: In directional and horizontal wells, the bit is subjected to stronger lateral forces and impacts. At this time, the lateral force resistance and impact resistance of PDC Cutter are particularly critical. I will pay special attention to the bonding strength of the PDC Cutter’s PDC layer to the substrate, and the toughness of the PDC Cutter itself. If the binding strength is not enough, it is easy to collapse or even drop teeth under the action of lateral force.

B. Selection process and considerations

Selection is like a system engineering:

1. Assessment of geological conditions: This is the first and most important step. Rock type, hardness (I will look at Rockwell hardness, compressive strength, etc.), abrasiveness, and the mysterious drillability index (DSI) are all data I focus on. These data can help me to judge the condition of the formation.
2. Drilling parameter matching: Drilling parameters have a great influence on the performance of Flat PDC Cutter. The speed is high, the wear of the cutting teeth will be accelerated, but the ROP may be higher; WOB (weight on bit) is large, the depth of cut increases, but the impact force also increases; flow affects chip removal and cooling. My principle is that the PDC Cutter must be selected to perfectly match the expected drilling parameters to form an efficient system.
3. Bit type adaptation: Flat PDC Cutter cannot exist independently, it must be attached to the bit. In conventional PDC bits, they are the main force; in hybrid bits, they may cooperate with tooth teeth and complement each other. Therefore, the positioning and role of Flat PDC Cutter in the entire drill system should be considered when selecting the type.
4. Economy and life cycle: everyone wants to use the best, but the cost is always a topic that cannot be avoided. I will balance the initial cost and the comprehensive drilling cost. Sometimes, the seemingly expensive Flat PDC Cutter, because of its long life and excellent performance, can bring lower cost per meter.
5. Success story analysis: This is especially important. I often look through previous drilling reports and analyze the successful application experience of Flat PDC Cutter in combination with specific work areas and formations. The experience of our predecessors is a valuable asset that allows us to avoid many detours.

PDC Cutter, as an important engine of drilling technology innovation, its development is endless. From the early basic models to today’s diversified and high-performance Flat PDC Cutter, and even the more intelligent and adaptive cutting elements that may appear in the future, every breakthrough embodies the wisdom and sweat of countless engineers. In this paper, we have deeply discussed the core technology, model characteristics (such as 1313, 1613, 1308, 1916, etc.) of Flat PDC Cutter and its application strategy in actual combat, aiming to provide a reliable reference for industry colleagues through professional knowledge, actual combat experience and rigorous analysis.

I hope that this sharing will not only help you better understand and apply Flat PDC Cutter, but also stimulate your enthusiasm for continuous exploration of these technical fields. Future drilling challenges will only become more complex, and PDC Cutter technology will continue to evolve in the direction of higher efficiency, longer life, and greater adaptability.