Development of Plasma Sprayed Coatings to Improve the Erosion Resistance of Wire Wrapped Screens

Abstract The installation of sand screens in wells can fail in one of two ways: by causing an unacceptable high pressure drop in the near wellbore area or by losing the ability to retain particles. Four mechanisms can lead to a failure: plugging, corrosion, erosion and mechanical deformation. To increase the lifetime under erosive conditions, a coating for wire wrapped screens was developed and tested. Erosion occurs, when formation particles hit the screen surface with high velocities or by continuous production of fines through the screen openings. The screen openings must keep a specified size in order to control the formation sand or gravel pack. If the opening size increases due to erosion, more particles are produced and erosion increases. A newly developed coating is put on the outside (i.e. facing the formation) of standard wire wrapped screens to make the slots resistant against erosion. 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. A test facility was built to investigate the erosion resistance of sand screens. It consists of a flow loop to circulate a slurry of water and particles through 2″ coupons. Samples of standard wire wrapped, metal mesh and coated screens were tested. The tests were conducted with flow velocities of up to 18.5 m/s and particles of up to 100 micrometer for up to 60 h. The screens where compared under consideration of optical criteria, mass loss and functionality. The coated screens showed no sign of wear on the outside and kept their initial slot size. The slots of uncoated wire wrapped screens more than doubled in some places, when eroded under the same conditions. To test the functionality of the samples, sand retention tests were conducted before and after erosion. Since there were no changes in slot width, the coated screens show the same retention capabilities before and after erosion, while metal mesh screens that were eroded under the same conditions lost their ability to retain sand. The newly developed coating improves the resistance against erosion, is able to withstand corrosive well environments and has mechanical properties suitable to be safely installed in any well. Therefore the coating has the ability to improve the lifetime of screens under erosive conditions.