Abstract
Both the high temperature and particle environment at the downhole greatly aggravate the abrasive wear and shorten the service life of the fluororubber (FKM) seal seriously in drilling engineering. At present, there is less awareness of the tribological behavior of seals in such complex working conditions. In this work, the abrasive wear performance of the thermally degraded FKM seal was tested in the form of simulating the intrusion of abrasive particles into the interface. Results show that the wear of both rubber seals and metal counterparts is exacerbated. Through the analysis of the wear scar morphology and friction coefficient, it is revealed that more abrasive caves scatter on the surface due to the mechanical degradation of the FKM. These abrasion caves reduce the tendency of particles to escape from the caves and prolong the abrasive action. Furthermore, the abrasion cave alters the particle motion from sliding to rolling, which leads to more caves generated on the surface of the hard tribo-pair. These results enhance the understanding of the abrasive wear for FKM seals and hopefully contribute to the promotion of seals used in hot abrasive particle environments.
Highlights
In drilling engineering, rubber seals are widely used to prevent drill cuttings from intruding into the seal chamber of the drilling tools, such as the roller bit, rotation guide tools, devices of measurement while drilling, etc. [1,2]
The results show that thermal treatment significantly reduces the tear strength, tensile strength, and elongation at break, the hardness of the rubber does not change significantly but only slightly increases
This study investigated the effect of thermal treatment on the three-body abrasive wear of FKM seals and analyzed the movement of particles in the frictional interface
Summary
Rubber seals are widely used to prevent drill cuttings from intruding into the seal chamber of the drilling tools, such as the roller bit, rotation guide tools, devices of measurement while drilling, etc. [1,2]. The working performance of the downhole seal is not satisfactory. It has been found that the service life of the rubber seal used under drilling conditions decreases significantly. The rapid failure of rubber seals is further exacerbated when it is used in the deep well, ultra-deep well drilling, and geothermal well drilling [3,4,5,6]. What these working conditions have in common, except the abrasive condition, is the high ambient temperature [7]. The well temperature could achieve 150 ◦ C when its depth reaches 5000 m (geothermal gradient: 25–30 ◦ C/km)
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