Research on bidirectional protection mechanism for wear and friction reduction of drill pipe joints in extra-deep wells

Abstract:

Aiming at the serious wear problem of the wear band and casing friction pair of drill pipe joint during drilling in deep， ultra-deep and extra-deep wells， the bidirectional protection model of drill string and casing wear and friction reduction was established in this study. The bidirectional protection mechanism of diamond composite wear band and casing was proposed， and the tribological properties of diamond composite wear band materials were verified by experiments. This study systematically explained the wear resistance and friction reduction bidirectional protection mechanism of diamond composite wear band material. By constructing a drillstring-casing mechanical model containing rock axial reaction and contact load， the friction and wear testing machine independently developed was used to conduct experiments， and the friction coefficient， wear amount and wear morphology characteristics were compared and analyzed under different working conditions. Combined with Raman spectroscopy， the mechanism of surface tribochemical reaction was revealed. The results show that through the synergistic effect of the hard phase support and self-lubrication， the friction coefficient of the diamond composite wear zone can be significantly reduced. The formed gradient composite protective layer and graphite transfer film can effectively achieve two-way protection between the drill pipe joint and the casing surface. The research results provide theoretical support and experimental basis for the structural optimization of wear band of drill pipe joints in deep wells.