Experimental and theoretical analysis of rock failure characteristics by a single PDC cutter under downhole pressurized conditions

Frontiers in Energy Research

Energy Research

Jianlin Yao¹  Hao Fu²  Yang Liu³  Zhun Rong³  Qi Zhang³  Shuang Yan³  Xianwei Dai⁴ 

[1] CCDC Petroleum Drilling and Production Technology, Deyang, China;Development Department, PetroChina Southwest Oil & Gasfield Company, Chengdu, China;Northeast Sichuan Gas District, PetroChina Southwest Oil & Gasfield Company, Dazhou, China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, China;

关键词: unconventional oil;    rock breaking;    pressurized conditions;    theoretical model;    PDC cutter;   

DOI  :  10.3389/fenrg.2023.1264804

 received in 2023-07-21, accepted in 2023-08-14,  发布年份 2023

来源: Frontiers

【 摘 要 】

The development of high-efficiency polycrystalline diamond compact (PDC) bits plays a major role in developing unconventional oil and gas. Thereby, a series of single cutter tests have been conducted in the past few years. However, most of them were performed under atmosphere conditions due to the limitation of the experimental setup. In the present study, a series of single cutter experiments were performed under pressurized conditions, in which both principal stress and hydrostatic pressures were loaded with a self-developed facility. The cutting force, topography of cutting grooves, and mechanical specific energy (MSE) were analyzed to evaluate rock failure efficiency. Furthermore, a theoretical model was developed to study stress evolution. Combined with experimental results, the rock failure mechanism and the effects of bottom hole pressures on rock breaking characteristics were revealed. The results indicate that the increase in principal stress and hydrostatic pressures cause larger cutting forces and reduced rock cutting efficiency. Additionally, a larger hydrostatic pressure will promote the propagation of subsurface cracks, leading to larger roughness of cutting grooves and facilitating the subsequent rock cutting process. In this study, the hydrostatic pressure has the greatest impact on rock failure process, followed by the principal stress when parallel to the cutting direction. Comparing the experimental and simulation results, we can find that only a fraction of cutting force is directly utilized in breaking rocks, while the remaining force is applied to overcome the friction induced by the flow of cuttings along the cutter surface. Consequently, measures should be taken to prevent bit balling and decrease the friction force, thus weakening the effects of hydrostatic pressures and improving the efficiency of PDC bits.

【 授权许可】

Unknown   
Copyright © 2023 Rong, Dai, Yan, Liu, Zhang, Fu and Yao.