Identification of Lithology Based on Vibration Response of Drill Bit

The evaluation of rock properties is an indispensable part of the process of developing deep oil and gas resources. Traditional lithology identification methods have limitations such as high cost and time consumption. During the drilling operation, the interaction between the drill bit and the formation occurs, and the dynamic vibration response of the drill bit can represent the geological characteristics of the formation. In this paper, the differences in vibration response during the drilling process are explored by experimental methods, and the feasibility of using vibration signals to judge the change in rock stratum is investigated. A full-scale drill bit rock breaking test rig is constructed, and laboratory experiments on full-size Polycrystalline Diamond Compact (PDC) bit rock breaking are carried out, during which vibration response data under different drilling parameters are collected. The differences among experimental datasets are then analyzed and compared, and key data characteristics are extracted. Based on these, a new method for discriminating formation lithology is proposed. The results show that the amplitude of vibration response is closely related to drilling parameters and rock properties. The frequency composition of the vibration is only affected by the properties of the rock strata and is not affected by drilling parameters. Furthermore, the model established based on differences in vibration responses can effectively identify lithological changes, with an identification accuracy rate exceeding 95%. This study offers a theoretical basis for identifying lithologic changes in field production and serves as a valuable supplement to existing methods.