PROFILE
Sand ingress into the wellbore is a major problem for reservoir engineers and can lead to a reduced rate of oil and gas production, erosion of completion and downhole tools, and damage to surface equipment. Sand control techniques are used to manage this problem in order to stabilise the reservoir and enhance productivity. Wire mesh sand screens are one method of sand control that helps mitigate against the negative impacts of sand and fines in a producing well. Conventional materials like 316L stainless steel and nickel-alloys are typically used for mesh sand screens and are very good for corrosion resistance, but offer only marginal protection against long-term sand abrasion and erosion.
CHALLENGE
A major multinational energy corporation and well owner wanted a coating solution to optimise the operational life of their wire mesh sand screens and maintain production volumes for a longer duration. Coating these multi-layer screens presented significant technical challenges due to the nature of the wire mesh weave and its small apertures.
SOLUTION
Hardide-T is a tungsten metal matrix coating with dispersed nano-particles of tungsten carbide. It is applied on metal components by chemical vapour deposition (CVD), crystallising from the gas phase atom-by-atom in reaction chambers. The coating is very hard, tough and forms a pore-free barrier against corrosion and acid attack. As a proven performer in severe service oil and gas environments, and capable of coating mesh with apertures as small as 150 microns, Hardide-T was selected as the coating to be developed for this application.
We worked closely with the operator and screen manufacturer to determine the performance criteria, coating expectations, product design, test procedures and trial program before undertaking coating production runs.
After initial sand erosion, acid resistance, tensile and coating thickness uniformity tests proved successful, the team optimised flow parameters, micron rating and base material options.
In sand/water slurry erosion testing (2.1% of 300 μm average silica sand in water with jet velocity 24 m/s and 90 degree impingement angle), the Hardide coating showed a 125x lower erosion rate than stainless steel.
At our in-house laboratories, we sectioned coated mesh screen samples and finished product to determine coating uniformity, thickness, hardness and overall quality. A detailed QC procedure is carried out for every coating run to ensure product quality and consistency. The coated sand screens then successfully passed rigorous mechanical testing by the operator to evaluate the risk of the tool bursting and collapsing under high pressure applied from inside or outside the screens. This confirmed the coated screens are robust and ready for field use in demanding conditions.
The development process took more than two years to complete. The Hardide-T coated sand screens are now installed in deepwater fields and reservoir simulation predicts a doubling of life expectancy with more consistent, longer production rates.
