Development of effective green lubricants for industrial drilling systems in aggressive environments
Creators: Palimi, Mohammadjavad
Publisher: name: University of Alberta Library
Year: 2024

<p>In drilling systems used in the oil and gas industry, drilling equipment often encounters critical problems which could result in irreparable damage to metallic equipment. Chemical and physical interactions at the contact between different parts, such as drill bits, drill strings with well walls and other hard materials, can cause wear and thus negatively affect the mechanical system&#39;s efficiency, sustainability, and safety. Moreover, the drilling operations often proceed in corrosive environments, which can deteriorate the performance of the drilling equipment. The most special concern is the synergistic attack by both wear and corrosion, referred to as tribo-corrosion, which can result in significant material loss, compared to those caused by wear and corrosion separately. Drilling fluids used to facilitate drilling operations are essential, which generate lubricating films to minimize direct contact between moving metal parts and surroundings for reduced friction, corrosion, wear, and synergistic wear-corrosion attack. Various factors, such as temperature, solution chemistry, contact force, sliding speed, and electrochemical potential, all can affect wear, corrosion, and tribo-corrosion in the drilling systems. Thus, comprehending the mechanisms of wear, and corrosion, the wear-corrosion synergy, and their effective preventative measures is essential to improve the drilling effectiveness and mitigate the mentioned issues.<br>
This research attempts to improve the corrosion, wear and tribo-corrosion resistance of carbon steel immersed in the drilling fluids. The study evaluated the effect of different green corrosion inhibitors containing various heteroatoms (O, N, P) on the corrosion, wear, and tribo-corrosion of steel in emulsion-based drilling fluids (WBEs) under static and dynamic conditions. Various concentrations of mineral oil as base oil, surfactant and corrosion inhibitors were added to the 5% KCl base solution to make highly stable WBEs, which were evaluated by dynamic light scattering technique, zeta potential measurements, turbidimetry and inverted light fluorescence microscope. Then, the CO2 corrosion-inhibiting effectiveness of inhibitor molecules on carbon steel in a rotating cylinder electrode system was studied using electrochemical tests, including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization analyses. In the following, a pin-on-disc tribometer incorporated into the electrochemical system under a linear reciprocating sliding module studied the anti-tribo-corrosion behavior of carbon steel immersed in the WBEs containing different corrosion inhibitors. The effectiveness of the different corrosion inhibitors in suppressing corrosive wear performance was thoroughly evaluated by measuring the coefficient of friction (COF), potentiodynamic polarization, current density, and potential evolution with time. In addition, the synergy between wear and corrosion was also measured. The surface morphology, chemical composition, volume loss, wear track profile, and specific wear rate of worn surfaces after tribo-corrosion experiments were examined by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectrophotometer (XPS) and 3D optical profilometer. The results showed that the green inhibitors significantly improved the emulsion-based fluids, evidenced by significant reductions in corrosion rate, COF and wear rate and wear-corrosion synergy. Finally, the effect of various controllable parameters such as contact force, sliding speed, electrochemical potential, and the concentration of corrosion inhibitor on the tribo-corrosion properties of steel samples immersed in WBEs were investigated. The study revealed the strong effects of the abovementioned parameters on corrosion potential, corrosion current density, COF, volume loss, corrosive wear, and adsorption rate of inhibitor molecules to the iron surface. </p>