Plasma-Sprayed Coatings Resist Erosion in Wire-Wrapped Screens

Abstract

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 21158, “Development of Plasma-Sprayed Coatings To Improve the Erosion Resistance of Wire-Wrapped Screens,” by Lukas Ochmann, SPE, and Mohd M. Amro, SPE, TU Bergakademie Freiberg, and Bernd Gronde, Fraunhofer IKTS Hermsdorf, et al. The paper has not been peer reviewed. Copyright 2021 International Petroleum Technology Conference. Reproduced by permission. _ A newly developed coating is put on the outside (i.e., facing the formation) of standard wire-wrapped screens to make the slots erosion-resistant. The coating consists of ceramic or hard metal and is applied by plasma spraying. An extensive development and verification program was conducted to guarantee defined slot widths, corrosion resistance, and mechanical strength of coating and screen. The coating improves resistance against erosion, can withstand corrosive well environments, and features mechanical properties suitable to be safely installed in any well. Thermal Spraying and Composition of Coatings The screens are coated using thermal spraying. This process uses a hot plasma jet to melt powdery materials and apply them to a solid surface. The molten particles solidify on the surface and form a hard coating with little porosity. No chemical reaction exists between the base material and the coating. Several different steps are necessary to coat a wire-wrapped screen. First, the screen is sandblasted in a distinct way to provide a defined surface roughness. After that, a thin bonding layer is applied by thermal spraying. This intermediate layer further improves the adhesion of the functional layer. This erosion-resistant main layer, which consists of hard metal or ceramic, is applied next by thermal spraying. The coating is finished by filling up the pores of the sprayed layers with a liquid sealer. The coating changes the geometry of the slots, slightly reducing the slot size and creating a less-sharp slot opening. By adjustment of the process parameters of the thermal spraying and choice of the correct initial slot width, defined and constant slot widths can be produced for the final product. Corrosion Investigation All samples and future prototypes are based on 1.4404 (316L) stainless steel. Combinations of four bonding layers, six functional layers, and five sealers were investigated. In total, 237 different samples were corroded under different conditions. The samples were submerged halfway into the brine so that the effect of the three-phase interface (brine, gas, and sample) could be investigated over a period of multiple weeks (minimum 3 weeks, maximum 18 weeks) at 60°C. Further experiments were conducted with nitrogen and hydrogen atmospheres for 3 weeks. The first tests were conducted with samples made from wire-wrapped screens. A second batch of tests was performed with coupons for tensile bond tests.