Abstract

Background: Rock abrasiveness is a factor with considerable influence on the wear of tools in well drilling. However, it is determined with various methods, which result in no uniform standard formed.

Objective: The goal of this work is to develop a wear calculation model of PDC compact and a prediction model of rock abrasiveness.

Methods: Studies on rock abrasiveness evaluation equipments were carried out in Northeast Petroleum University. Among these patents, one is the device to simulate the wear of drill bit in strata during the real drilling process. Firstly, based on the rock cracking conditions, the force calculation model of the compact is established. Since the actual contact area between the rock and the compact only appears on the tiny part of the apparent area, the real force of particles involved in the wear and the bottom of the compact is obtained according to the probability density distribution of the quartz content. Then, based on the geometrical principle of abrasive wear, the wear calculation model of the compact is established. Finally, the model is modified using the above abrasiveness patent.

Results: The model revealed the order of the rock parameters affects the wear of the compact as follows: elastic modulus> quartz content> internal friction angle> surface roughness> Poisson's ratio> cohesion. So the evaluation index of rock abrasiveness was established and the grading standard of rock abrasiveness was developed finally.

Conclusion: They can provide guidance for predicting formation abrasiveness and the design and optimization of the drill bit.

Keywords: Rock abrasiveness, rock mechanics, rock cracking, PDC compact, wear model, abrasive wear, abrasiveness device.