Abstract
Generally, oil tubing and casing connections made of carbon steel are connected using phosphate-treated coupling, but high-grade steel oil casing can only be connected using copperized couplings, which are expensive and result in environmental pollution. A new anti-friction coating was prepared by adding suitable amounts of nanoparticles into a highly pure and concentrated nano-copper suspension, with epoxy resin as a binder. Laboratory tests and full-scale make and break tests show that a heterogeneous copper layer is formed after curing when this coating was applied to the phosphate layer surface of couplings made of P110 and P110S casings. This can greatly reduce the make-up torque of casing thread, and can effectively improve or even eliminate galling of high-grade steel oil casing.
Highlights
Oil-casing pipes are widely used for drilling in oil wells; as many casing pipes and threaded couplings are used in such oil wells, the failure of even one casing pipe or coupling can result in huge economic losses
The range of friction coefficients is larger for the reference sample, and reduces gradually with time
It can be seen that, compared to the reference sample, the friction coefficient for the AF-01 sample hardly changes on increasing the load from 2N to 5N and 10N
Summary
Oil-casing pipes are widely used for drilling in oil wells; as many casing pipes and threaded couplings are used in such oil wells, the failure of even one casing pipe or coupling can result in huge economic losses. Epoxy resins contain polar hydroxy and epoxy groups, which help to improve the invasive and adhesion force of entering into phosphate layer and have excellent bonding properties with the metal matrix[12] Both nano-copper and nano-PTFE particles have good anti-wear and anti-friction properties; nano-copper particles, in particular, can be used in a heavy-load, low speed, and high temperature vibration environment[13,14].This coating was named AFRICO AFRICO forms a thin nano-copper film after curing when it is applied on the surface of the phosphate layer of API (American Petroleum Institute) or non-API couplings; this coating shows excellent anti-friction effect during make-up and can effectively reduce friction and make-up torque between the threads to improve the anti-galling property of tubing and casing
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