OS ZINC OXIDE - Sulphide Scavenger
Hydrogen sulphide is a flammable, colourless gas that is extremely toxic at low concentrations and represents one of the most hazardous issues encountered in oil and gas well drilling. It is of critical importance to treat hydrogen sulphide with appropriate scavengers. Simply maintaining high pH or using oil-based fluids with excess lime is at best a temporary measure and can lead to dangerous levels of hydrogen sulphide being liberated from the drilling fluid.
OS ZINC OXIDE scavenger reacts with sulfides to form ZnS. This precipitate is an insoluble, inert, fine solid that remains harmlessly in the mud system or is removed by the solids-control equipment. OS ZINC OXIDE can be used in any type of drilling fluid.
Typical Physical Properties
Appearance - Off white powder
S.G. - 5.4 – 5.6
Bulk Density - 2,627 kg/m3
Zinc Oxide - Min. 99.7%
Metallic Metals (as Zn) - None
Moisture - Max 0.4%
Insolubles in HCl solns - Max 0.04%
Solubles in Water - Max 0.6%
Screen Residues (45 u m wet screen) - Max 0.32%
Loss on Ignition - Max 0.6%
OS ZINC OXIDE has a higher percentage of zinc (>80% by weight) compared to competitive sources of zinc, such as basic zinc carbonate, zinc sulfate or zinc chromate.
OS ZINC OXIDE is finely ground and offers a high surface area for fast, efficient removal of the hydrosulphide and sulphide ions.
OS ZINC OXIDE is not pH-dependent; it is effective at very alkaline pH, such as 11.5 to 12.5, whereas iron materials are less so.
Helps remove the hazard of dangerous H2S gas escaping at the surface.
Lessens the possibility of hydrogen embrittlement occurring on downhole tubular.
It is recommended that a pH above 11 be maintained whenever H2S is expected. This high alkalinity converts the dangerous H2S gas to less toxic bisulfide (HS-) and sulfide (S2-) ions. The OS ZINC OXIDE then reacts to form an insoluble Zinc Sulphide precipitate, removing the potential for subsequent release of H2S.
The initial treatment of OS ZINC OXIDE scavenger is usually 1 to 2 lb/bbl (3 to 6 kg/m3).
Subsequent field treatments should be based on approximately 1 lb/bbl (3 kg/m3) of Zinc oxide scavenger per 600 mg/L of sulfides detected.
On a stoichiometric basis, 1 lb/bbl (3 kg/m3) of Zinc oxide scavenger removes 1100 mg/L of sulfides.
Removal is always less effective under actual field conditions so it is recommended to maintain an excess of OS ZINC OXIDE in the circulating system. Use a Garrett Gas Train and proper Drager tubes to measure the sulfide content. Zinc oxide scavenger should be added through the hopper.
OS ZINC OXIDE is packaged in 25 kg sacks.