Accurately identifying the damage failure modes and causes of PDC cutters and PDC drill bits is a key step in the drilling tool selection and the drill bit iterative optimization. To improve the accuracy and objectivity of drill bit damage identification，failure analysis was conducted on hundreds of PDC bits tripped out of wells，and the main damage failure modes and causes of PDC cutters (including various shaped cutters) were summarized，leading to a dataset containing over ten thousand images of PDC cutter damage morphologies. Then，based on the convolutional neural network-based YOLOv7 image recognition algorithm，an intelligent recognition model for PDC cutter damage failure was established. This model can effectively infer damage types from PDC cutter images and automatically annotate the images with corresponding damage failure modes. The model was evaluated using multiple performance metrics，showing an identification accuracy of over 80%. Furthermore，this model was combined with the PDC drill bit design theory and damage failure mechanisms to develop a new intelligent recognition method for PDC drill bit damage failure，using statistical methods like causal inference. This method can automatically evaluate the damage failure modes of PDC cutters in different regions of the bit crown using only photos of bits tripped out of wells and determine the primary cause of PDC drill bit failure. The research findings provide references for intelligent drill bit damage identification and innovation in intelligent drilling technology.

With oil and gas exploration and development approaching the deep-burial，deep-water and unconventional fields，the encountered formations become increasingly complex. Deep mudstone formations exhibit strong hard plastic characteristics during drilling，resulting in difficulties in penetrating of cutters into formations and low rates of penetration （ROP）. Given the challenge of improving ROP in hard plastic mudstone，rock-breaking simulation tests of PDC （Polycrystalline Diamond Compact） cutters were conducted for hard plastic formations，and the rock-breaking effects of various shaped cutters were analyzed. The results indicated that the 3D-shaped cutter exhibits the best rock-breaking efficiency and certain durability: it delivers a maximum ROP improvement of 116.4% in the hard plastic mudstone in Shengli Luojia Oilfield. Furthermore，a staggered cutter arrangement design，combining axe-shaped and 3D-shaped cutters，was proposed for drilling deep and complex formations，like sand-mudstone interbedding formations，which delivers the highest ROP increment of  215.7% in Yongjin Oilfield in Junggar Basin. Additionally，potential measures for enhancing ROP in hard plastic mudstone were discussed. The design principles of "sharp breakthrough，plane advancing and intensive scraping with small-diameter cutters" are recommended to improve the drilling efficiency. The research findings provide valuable insights for optimizing the design of PDC bits for hard plastic mudstone.