Diamond-like carbon (DLC) coatings are recognized in many sectors as a promising way of controlling wear and the corrosion performance of components. DLC coatings are well established in the automotive industry where they are applied to the moving parts of direct injection fuel systems operating under frictional conditions at high pressures and in the aggressive environment of the combustion chamber. Over the last few years, there have also been an increasing number of reports of DLC coating applications in oil and gas production contexts, including in pipes, shut-off gates and various types of valves. This paper reviews current efforts to use DLC coatings in the oil and gas sectors and analyses typical coating degradation mechanisms including wear and wear-accelerated corrosion regimes. DLC coating deposition techniques including Physical (PVD) and Chemical Vapor Deposition (CVD) techniques are elaborated and the unique coating properties obtained from those two methods are assessed. Surface functionalization is discussed including dopants (W and Si) and gradient interlayers. Finally, the outlook for future use of DLC coatings in oil and gas production is discussed.
Fusion Bond Epoxy (FBE) coating system was exposed to 5% sodium hydroxide at elevated temperature for 30 days. The result of exposure showed formation of adhere deposit layer, a discolored zone underneath and remaining un-affected bulk of the coating. The deterioration of the coating was characterized using analytical techniques like scanning electron microscopy (SEM), energy-dispersive X-ray (EDAX) spectroscopy, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC), pull-off adhesion, and electrochemical impedance spectroscopy (EIS). Results obtained indicated chemical deterioration of the coating in the discolored zone and leaching of low molecular weight coating component forming deposit layer. Although the adhesion strength and barrier property were not affected, the polymer matrix in the affected zone undergoes severe changes in its surface microstructure, primary chemical structure, and glass transition temperature. This may inflict serious impairment of the coating functional properties and premature failure of the coating in long term exposure.
Summary
BaSO4 scale containing Naturally Occurring Radioactive Material (NORM) as well as calcium carbonate scale has been reported in gas production facilities in conjunction with the Antrim play in northern Michigan. The scale study was undertaken by the Water Research Institute, Inc. (WRI) under contract from the Gas Research Institute. It was proposed in the scale study to conduct a two phase systematic characterization of BaSO4 scale from the Michigan Basin area both as to occurrence and environmental hazard, and to evaluate scale control methods using brines typical of the area. The initial study involved sample collection and analytical work-up to arrive at a correct theoretical analysis of the problems involved. The variability of the sulfate concentrations in the wells is addressed and scale prediction techniques applied to the reservoirs and the surface equipment to determine where scale was forming and where it is likely to form. The scale is proposed to be forming due to the commingling of produced waters from wells with high sulfate concentrations with waters from other wells relatively high barium concentrations. Inhibitor evaluations were done using a high temperature-pressure laboratory apparatus developed at Rice University and WRI (patent application pending with GRI) and effective chemicals and probable dose rates for inhibition were determined. Concurrently, studies were begun by Bioindustrial Technology, Inc. and United Exploration and Development Consultants to learn the sources of the high sulfate concentrations reported in some wells in the area and to determine the causes of souring in some others.
In addition to the scale forming in the surface facilities, NORM scale was predicted and found in production tubing from individual wells. The driving forces for scale precipitation in these wells is the temperature and pressure changes resulting from production Chemical squeeze of inhibitor into the reservoirs and surface injection are recommended to treat and eliminate the scale problem.
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