Innovative PDC Cutter with Elongated Ridge Combines Shear and Crush Action to Improve PDC Bit Performance

Abstract

Most traditional polycrystalline diamond compact (PDC) cutting elements have a flat polycrystalline diamond table at the end of cylindrically shaped tungsten carbide body. During drilling, the flat diamond table engages the formation and shears the rock layer by layer. A new ridge-shaped diamond cutting element (RDE) has a similar cylindrical tungsten carbide base; however, the diamond table is shaped like a saddle with an elongated ridge running through the center of the diamond table and normal to the cutter axis. The intended cutting portion, the "ridge," engages the formation to fracture and shear the rock at the same time. The design intent was to create a unique cutting element that could combine the crush action of a traditional roller cone insert and the shearing action of a conventional PDC cutter. The new cutting elements were tested in the laboratory against standard flat PDC cutters in a rock-cutting evaluation, and later the new elements were applied to PDC bits and run under real drilling conditions. The laboratory rock-scrape tests indicated that the new cutting element not only enables the cutter to efficiently shear formation in the same way as a conventional PDC cutter, but also delivers a crushing action similar to a roller cone insert. Preliminary results indicated a reduction of roughly 40% in both cutting force and vertical force on the new ridged diamond element cutters (RDE) over a conventional PDC cutter. Similar findings were also observed during the rock-shearing test on a vertical turret lathe (VTL). Subsequent field tests in multiple areas in North America have produced faster rates of penetration (ROP) in most of the cases. The trials indicate that the new cutting element is efficient at removing rock, and a bit equipped with these elements requires less mechanical specific energy (MSE) during drilling than does a bit with a conventional PDC cutter. In addition, the reduced cutting forces reduces bit torque and thus improves the drilling tools’ life and the bit directional performance. Field data has proven this technology improves drilling performance in terms of ROP and footage over the current PDC bits fitted with traditional flat PDC cutters.

Application of an innovative ridge-ladder-shaped polycrystalline diamond compact cutter to reduce vibration and improve drilling speed

“…It is known from damage mechanics that rock destruction is not a state but a process. Figure 12 shows a characteristic stress-strain curve of a rock, which indicates that there are three main stages from starting bearing load In Figure 12, the damage factor D can be expressed as equation (8). 17 Based on this, we can say that rock damage has two forms, one is yield stress softening D s and the other one is the degradation of elasticity (1…”

“…In the drilling process, the conical PDC cutter applies a concentrated point load to break rocks by plowing, and then the general PDC cutter creates a more efficient and durable shearing action. Crane et al 8 introduced a PDC cutter with an elongated ridge which fractures and shears the rock at the same time, improving the rock-breaking efficiency of drill bits. Al-Ajmi et al 9 developed a PDC cutter with a unique cutting structure to increase the stress concentration acting on the rock, offering more efficient cutting action than the general PDC cutter.…”

3D Numerical Simulation of Rock Cutting of an Innovative Non-Planar Face PDC Cutter and Experimental Verification

“…Currently, polycrystalline diamond compact (PDC) bits are mainly used for drilling soft to medium hard formations. While in hard abrasive formations serious failures, such as chipping, broken cutter and falling off of the PDC, often occur and the drilling effect is not satisfactory [1][2][3][4], which is difficult to meet the exploration and development needs of unconventional resources in deep formations [5,6]. To improve the performance of conventional PDC bits in deep formations, a series of approaches has been conducted on the material refinement and the design method supplement, such as increasing the number of cutters and blades [7], optimizing diamond packing [8] and using high-temperature and high-pressure (HT/HP) sintering for higher diamond volume in the PDC layer [9,10].…”

“…Later, Schlumberger Company also introduced its innovative cutter-the Axe cutter, which combines a standard cylindrical substrate with a modified ridge diamond layer ( Figure 1(b)). Field tests indicate that this cutter improves drilling performance in terms of rates of penetration (ROP) and footage over the current PDC bits [1]. In 2015, Sifangda Company in China produced an innovative cutter with three cutting edges, called the 3-RDE cutter.…”

“…The 3-RDE cutter-rock interaction is quietly different from the conventional cutter owing to its unique structure. There are mainly three aspects: (1) The convex edge of 3-RDE cutter, act as a "sharp point" to fracture the rock, which is similar to the crush action of a traditional roller cone bit; (2) the 3-RDE cutter consist of two working faces at the both sides of the convex edge, which can performs the bevel cutting and make the debris automatically formed into two branches that extruded across the working surfaces; and (3) the thickness of 3-RDE cutters' PDC layer is greater than the conventional cutter, which indicates the 3-RDE cutter has higher wear and impact resistance.…”