With oil and gas exploration advancing towards deep, ultra-deep, and extra-deep reservoirs, complex geological environments have imposed stringent demands on drilling tools. This paper systematically reviews the rock-breaking mechanisms, failure modes, material and structural optimization, and the current status of intelligent development of Polycrystalline Diamond Compact (PDC) bits in deep complex formations, providing theoretical support and engineering references for high-efficiency bit design. By summarizing single-cutter experiments, numerical simulations, microstructural analyses, and field data studies, this paper analyzes plastic-brittle failure patterns of rocks under various formation conditions and their effects on cutting forces, mechanical specific energy (MSE), and cutting morphology. It systematically categorizes typical failure modes of PDC cutters, including wear, impact, and erosion. Furthermore, it evaluates recent progress in cutter material modification, shaped cutter design, global cutter layout, and hydraulic structure optimization technologies regarding their roles in enhancing rock-breaking efficiency and bit lifespan. The paper also outlines the research and application of smart bits and machine learning-based bit selection methods in deep drilling operations. Material and structural optimization can enhance the adaptability of PDC bits in deep oil and gas drilling, while intelligent technologies provide effective support for bit selection, lifespan prediction, and operational safety. The future development trend of PDC bit technology should focus on the deep synergy of materials, structures, and intelligence to achieve efficient rock breaking and optimize drilling operations in deep and complex formations.

High-voltage electric pulse(HVEP)drilling has become a new and efficient rock breaking method, which is also the research focus in the field of drilling speed increase. To probe into rock breaking mechanism of high voltage electric pulse, this study establishes a two-dimensional numerical model of multi-physical field coupling electric breakdown of single pair of electrodes. The model reproduces the generation of plasma channels in homogeneous red sandstone from the coupling of current field, electric breakdown field and circuit field. This paper analyzes the effect of electrode pair angle, voltage and electrode spacing on rock electrical breakdown(that is, the formation of plasma channel in rock). The model includes the circuit structure parameters of pulse tool, the occurrence and development of electrical breakdown, and the relationship between electrical breakdown intensity and time. Results indicate that the plasma channel begins to sprout from the partial area near the top of the discharge electrode and develops towards the partial weak dielectric strength. With the voltage value of loading pulse increasing gradually, the time of electrical breakdown decreases gradually; comparatively, the equivalent failure volume of rock model increases gradually, and there is a positive correlation between them. On the precondition that the rock can be electrically broken, increasing the electrode spacing can improve the rock breaking efficiency of high voltage electric pulse. The equivalent failure volume of rock shows significant fluctuations during the gradual increase of electrode inclination angle of discharge electrode, and its extreme value mostly appears in the range of electrode inclination angle of 35°~ 55°. To further promote the industrial application of high-voltage electric pulse rock breaking, this paper proposes a three-dimensional numerical model of multi-physical field coupling dynamic electric breakdown of red sandstone based on two-dimensional model, reproducing the appearance of the fracture crater in the rock during the rock breaking process with electrode bit. At the same time, the self-designed coaxial electrode bit is selected for experiments of electric breakdown, and the laboratory experimental results of electric breakdown confirm the simulation experimental results.