| dc.description.abstract | Comprehensive evaluation on the influence of select commercial friction-modifying additives on the tribological performance of water-based mud will enable more widespread usage of waterbased mud (WBM) with confidence as a replacement for conventional oil-based mud (OBM). OBM is well known for a wide range of concern-raising issues/disadvantages, for oil & gas exploration and production drilling activities, especially adverse environmental effects. During the drilling process, the drill bit and stationary pipe wall are in contact, and under certain conditions, may experience severe metal-on-metal friction and reach extremely high surface temperature within very short period of time due to excessive heat generation, which simultaneously expedites vaporization of drilling fluid leading to boundary or starved lubrication conditions. The high surface temperature combined with the high pressure inside the wellbore, together imposes a risk of seizure between the contacting parts, which, essentially is a form of self-welding/diffusing bonding due to element migration. Similarly, the extreme conditions under high-pressure and high-temperature (HPHT) in nuclear reactors also renders the mechanical system subject to this phenomenon. Whenever seizure or self-welding occurs, the whole system, for both drilling system and nuclear reactors, will be forced to experience overhaul due to system failure, as a result of paralyzed operability. This study is dedicated to a systematic investigation on the tribological performance improvement of WBM focused on its potential as a promising replacement for OBM with the aid of select commercial friction-modifying additives, and the tendency and behavior of self-welding between metallic components of drilling systems and nuclear reactors, respectively. Various state of the art instruments for material characterization were utilized to aid in understanding the underlying mechanisms of the phenomena observed and test data obtained. The test data shows that with the influence of certain additives, the tribological performance of WBMs could be brought to a level where they are as good as, or even outperform conventional OBM for oil and gas drilling applications. Work on the self-welding behavior of nickel alloy shows that even in the absence of reducing (air) medium but only inert atmosphere, self-welding phenomenon does occur and could demonstrate significantly high bonding strength, which is of critical importance to the operability and reliability of nuclear reactors and other high-temperature applications. | en |
