High frequency surface treatment methods and apparatus to extend downhole tool survivability
A downhole device with compressive layer at the surface thereof. Such devices may be particularly well suited for survivability in the face of potentially long term exposure to a downhole environment. Techniques for forming protective compressive layers at the surfaces of such devices may include positioning devices within a chamber for bombardment by high frequency particles. As a manner of enhancing the compressive layer thickness and effectiveness, low temperature conditions may be applied to the device during the high frequency treatment.
1. A method of treating a downhole device for exposure to an environment of a hydrocarbon well, the method comprising:
positioning the device in a chamber adjacent an high frequency generator;
applying a frequency to the chamber with the generator to form a compressive layer at a surface of the device with high frequency particles; and
reducing the temperature of the device to less than about 0° C. during said applying to increase a thickness of the layer.
2. The method of claim 1 wherein the frequency is between about 50 Hz and about 25 kHz.
3. The method of claim 1 wherein said reducing is achieved via introduction of a temperature reducing fluid to the chamber.
4. The method of claim 3 wherein the fluid is cryogenic.
5. The method of claim 4 wherein the fluid is a liquid of one of nitrogen, carbon dioxide and argon.
6. The method of claim 1 further comprising rotating the device in the chamber during said applying.
7. The method of claim 6 wherein said rotating promotes one of uniformity in a thickness of the layer and an increase in a rate of formation of the layer.
8. The method of claim 1 wherein said applying comprises:
focusing a delivery of the particles to the surface; and
moving the device in the chamber to expand the delivery across the surface.
9. The method of claim 1 further comprising treating portions of the device with a laser peening application following said applying.
10. The method of claim 1 further comprising: coating the surface with a dye prior to said positioning; and visually examining the surface following said applying to confirm an effectiveness of the treating.
11. The method of claim 1 further comprising delivering a protective overlay to the layer.
12. The method of claim 11 wherein the protective overlay is an ultra-fine powder comprising one of chromium, molybdenum and nickel.
13. An assembly for high frequency treatment of a downhole device, the assembly comprising:
a chamber for accommodating high frequency particles and the device, the particles selected from a group consisting of ceramic, steel and chromium; and
a high frequency generator coupled to the chamber for inducing the particles to bombard a surface of the device at a given frequency to form a compressive layer thereat.
14. The assembly of claim 13 wherein the particles are between about 0.5 mm and about 10 mm in diameter.
15. The assembly of claim 13 wherein the particles include a material for alloying with the surface during the inducing.
16. The assembly of claim 13 further comprising a rotation mechanism for rotating the device in the chamber during the inducing.
17. The assembly of claim 13 wherein said chamber further accommodates a temperature reducing fluid to increase a thickness of the layer.
18. The assembly of claim 13 wherein the device is a tubular with a temperature reducing fluid therein to increase a thickness of the layer at an outer surface thereof exposed to the particles.
19. The assembly of claim 13 wherein the device is a tubular accommodating the particles therein, said chamber further accommodating a temperature reducing fluid to increase a thickness of the layer at an inner surface of the tubular.