The PDC - roller cone composite drill bit is composed of a PDC fixed - cutting structure and a roller - cone cutting structure. It has strong formation adaptability for complex and hard - to - drill formations. It exhibits high rock - breaking efficiency and a fast mechanical drilling speed in hard formations, abrasive formations, tight shale, and non - uniform formations (such as conglomerate - bearing formations). The teeth on the roller cone break the rock through impact and crushing, creating a broken pit at the bottom of the well. This not only makes the bottom of the well uneven but also weakens the strength of the bottom - hole rock. The roller cone plays a major role in breaking complex formations. The PDC teeth scrape and break the rock in soft - to - medium - hard formations while maintaining a high cutting efficiency.