*Applications of Polycrystalline Diamond (PCD) Materials in Oil and Gas Industry DOI: http://dx.doi.org/10.5772/intechopen.107355*

that is, these extreme temperatures can cause diamonds to return to graphite. High pressure is also necessary for the success of diamond sintering. In order to maintain the stable phase of the diamond, high pressure must be maintained during the sintering process. This usually requires a pressure of about 5.5 GPa or more. In this state, the diamond is stable in the sp3 structure and can be sintered without considering the significant degradation of the diamond raw material. In the design and operation of the HPHT system, the system will reach the required pressure of 5.5 GPa and 1427°C while maximizing the life expectancy of expensive hard metal tools such as anvils and molds. PDC cutters and synthetic diamond manufacturers are constantly striving to improve the performance and cost-effectiveness of their HPHT systems so that more extreme sintering conditions can provide the next generation of high-performance drilling products. In order to achieve these high temperatures and pressures at the same time, cubic pressure technology development is the key. The cube press consists of six large pistons, each of which can provide thousands of tons of force. Each piston pushes a small tungsten carbide anvil, which in turn compresses a cubic pressure unit containing the starting material (cemented carbide and diamond powder). Once the cube is pressed to reach the desired pressure, the current generates the desired high temperature through a resistance heater embedded in the pressure unit. These conditions are maintained long enough to ensure that a complete diamond-diamond bond is formed among diamond particulates to make the diamond bulk. However, the pressure is limited to a maximum of 10 GPa because the graphite heater will be transferred to the insulated diamond and lose its heater function.

One of the challenges in improving PDC cutter performance through traditional HPHT processes is the removal of Co, a key component in the formation of a robust diamond-to-diamond bond structure during PDC cutter manufacturing but is also the main cause of these problems in drilling applications. The entire industry has been researching and improving leaching methods or other methods to reduce the adverse effects of Co. On the bright side, the removal of Co improves the thermal stability of PDC tools by reducing the tendency to graphitization at high temperatures and preventing accelerated cracking caused by the above thermal stresses. On the downside, removing the Co phase tends to reduce the fracture toughness of PDC tools. Therefore, PDC cutter suppliers often offer Co leaching at different depths depending on the application requirements. Currently, there are no "standard" tools, but a range of tool leaching designs that suit different drilling requirements. The industry's best desire is to raise the degradation temperature from the usual 750–1200°C through cobalt leaching. Zhan et al. [4] made the thin film with a scanning electron microscope (SEM) showing what happens when the PDC sample is heated under mimic reservoir conditions. The end result is thermal failure, darkening the material when irregular cracks appear, turning the once uniform surface into something similar to the cracked mud seen at the bottom of a dry pond. There is a solution to this problem, called the deep leaching technique, which leaches most of the cobalt by immersing the PDC in the acid. But it also has its limitations, as some metals are sealed in spaces that liquids cannot reach and are left behind. The industry as a whole is researching (improving) leaching methods or other methods to further reduce the impact of cobalt. Across the industry, PDC cutters aim to be able to withstand the resulting high temperatures when cutting hard, variable formations. The industry's rule of thumb is that high temperatures can damage PDCs above 750°C, and leaching pushes this limit up to around 1200°C. One of the emerging technologies identified as technological breakthroughs is that through UHPHT technology that can manufacture PDC cutters without the use of metal catalysts [13, 14]. In this chapter, a range of new ultra-strong catalyst-free PDC cutting materials using innovative UHPHT technology has been

successfully synthesized and tested. These catalyst-free or binderless PDC cutting materials are more than twice as hard as current PDC cutting machines. As a result, new industry records for wear resistance are more than three times higher than traditional PDC cutters used in the oil and gas drilling industry. The new material also has fracture toughness close to that of metals. In addition, these catalyst-free PDC cutters do not require any expensive and time-consuming leaching process to remove the Co catalyst. With these super-strong catalyst-free PDC cutting elements on PDC drill bits, the possibility of achieving the game-changing goal of "one run to total depth", especially in drilling, hard formations is explored.
