Numerical Simulation and Field Test of a PDC Bit with Mixed Cutter Arrangement to Break Non-Homogeneous Granite

Abstract

As the depth of petroleum drilling increases, the strata environment becomes more complex. The efficiency and lifespan of Polycrystalline Diamond Compact (PDC) drill bits fail to meet current drilling demands. However, the structure and arrangement of PDC cutters are valuable determinants of drilling efficiency, although related research still has gaps and deficiencies. This study focuses on PDC cutters in axe, triangular prism, and circular forms. It establishes an inhomogeneous granite model based on the actual measurements of granite and verifies the accuracy of this model through uniaxial compression simulation. Finite element models of three types of cutters in various combination schemes are constructed to examine rock-breaking effects, with the best scheme optimized using Box-Behnken response surface methodology. The rock-breaking process of the optimal PDC drill bit layout has been compared to that of a single cutter bit. Field drilling has demonstrated the effectiveness of a mixed cutter arrangement. The results show that the inhomogeneous granite model can be trusted. The optimal arrangement involves axe cutters in the front row and an alternate arrangement of triangular prism cutters and axe cutters in the back row. The optimal lateral and longitudinal distances for the triangular cutters from the front row of axe cutters are 10 mm and 7 mm, respectively, while those for the back row of axe cutters from the front row are 10.06 mm and 7 mm, respectively. The ROP standard deviation in the drilling process of mixed cutter bits decreases by 53.06% and 43.08% compared to axe and triangular prism cutter bits, respectively. The drilling efficiency increases by 16.8% and 16.6%, respectively, demonstrating higher efficiency and stability. Field drilling results indicate that a mixed cutter bit increases efficiency by 23.5% compared to a bit with only triangular prism cutters. This study posits that research on the combination schemes and parameters of PDC cutters can significantly enhance drilling efficiency, thereby reducing the drilling cycle and costs.

Structure Design of Bionic PDC Cutter and the Characteristics of Rock Breaking Processes

“…Moreover, by considering both Figure 15a,b together, it can be observed that the axe cutter achieves higher rock-breaking efficiency compared to the triangular prism cutter, but with weaker stability. This is consistent with our previous research findings [16].…”

“…This indicates that the bionic cutter has great potential in enhancing the efficiency of rock breaking for drill bits and can provide significant support for field applications. Furthermore, in our previous research, the structurally symmetric triangular prism cutter exhibited higher stability and efficiency in rock breaking in complex hard formations compared to the axe cutter, which had a stronger aggressive ability [16]. However, in this study, the efficiency of the axe cutter was found to be higher than that of the triangular prism cutter, indicating that the axe cutter with stronger aggressive ability has an advantage in breaking softer formations.…”

“…The diameter of the drill bi 215.9 mm, and the cutters are installed on the drill bit with a back rake angle of 15°. Th are a total of four cutting wings, and the arrangement of the cutters follows the princi of equal cutting volume [16]. To validate the performance of the cutters on the drill bit, a full-scale drilling structure containing triangular prism cutters, axe cutters, and bionic cutters was constructed using SOLIDWORKS 2022 software, as shown in Figure 12.…”

“…The diameter of the drill bit is 215.9 mm, and the cutters are installed on the drill bit with a back rake angle of 15 • . There are a total of four cutting wings, and the arrangement of the cutters follows the principle of equal cutting volume [16].…”

“…The diameter of the drill bit is 215.9 mm, and the cutters are installed on the drill bit with a back rake angle of 15°. There are a total of four cutting wings, and the arrangement of the cutters follows the principle of equal cutting volume [16]. The cutting structure of the drill bit was imported into ABAQUS 2023 software to construct a finite element model of its interaction with the rock, as shown in Figure 13.…”