Hydrogen Sulphide Contamination of Crude Oil

Problem

Hydrogen sulphide contamination of crude oil threatened closure to a well head on one of the Chevron UK operated Ninian North Sea oil platforms owing to resultant H₂S gas handling constraints and corrosion of valuable plant.

These conditions called for the introduction of an H₂S scavenging agent right at the well head to de-sour the crude oil before contact with any further plant.

A mixer was required which could:

• operate completely effectively to ensure neither the scavenging agent nor the hydrogen sulphide remained resident beyond the flowline
• operate at a very high pressure (c 350 bar)
• be corrosion resistant itself
• be very space efficient

Total quality assurance was paramount owing to the very high value of the installation and time was vital every day meant lost production.

Solution

Chevron engineers selected Statiflo to solve the problem.

Statiflo engineers developed a static mixer using an extra strong corrosion resistant alloy Hastelloy C276 in a tailor made configuration designed to allow a three element mixer to be integrated into a long radius bend situated directly on top of the production well head. Additionally, specialist high pressure quick release end connections were incorporated to conform to oil industry standards.

The design fully met Chevron’s exacting requirements and has been operating to the full satisfaction of Chevron engineers since January 1989.

Result

Without the successful introduction of H₂S scavenging with the use of the inline mixer, this well head could not have operated since millions of pounds worth of downstream processing and associated gas equipment might have been damaged by the corrosive crude oil and gas. The static mixer allowed the corrosive scavenger to contact the H₂S rapidly and thus prevent either chemical or H₂S to exit the flowline.

With the use of Statiflo’s Motionless Mixer technology a valuable revenue stream has now been reinstated.