Part No. 197-01 Garrett Gas Train Test

Measures the concentration of soluble sulfides and soluble carbonates

The Garrett Gas Train (GGT) measures the concentration of sulfides or carbonates in drilling fluids and drilling fluid filtrates. This measurement gives a quantitative indication of the rate and amount of intrusion of hydrogen sulfide or carbon dioxide from the formation in the drilling fluid.

The Garrett Gas Train kit contains all hardware and reagents required to conduct the procedure according to API Recommended Practice 13B-1, ANSI/API 13B-1/ISO 10414-1. Two types of Dräeger tubes are supplied to adequately span the range of hydrogen sulfide concentrations that may be found in water based drilling fluid filtrates and in oil based drilling fluids. CO₂ Dräeger tubes and 1 liter gas bags are supplied for determination of carbonate concentration. Inert carrier gases, both  CO₂ and NO₂ are supplied for all tests. All items are securely packaged in a waterproof, high-impact plastic carrying case.

Hydrogen Sulfide Test Paper discs (supplied) can be used in the Garrett Gas Train to give a qualitative indication of the presence of sulfide. If the presence of sulfide is indicated by darkening of the paper disc, a Dräeger tube should be used for quantitative analysis.

Sulfides

Soluble sulfides include H₂S and the sulfide (S^2-) and bisulfide (HS^-) ions. Drilling fluid filtrate is acidified in a Garrett Gas Train, converting all sulfides to H₂S which is evolved by bubbling an inert carrier gas through the sample. The gas train separates the gas from the liquid. The gas stream is passed through a Dräeger tube which responds to H₂S by darkening along its length. The darkened length is proportional to the total sulfide in the drilling fluid filtrate. The low-range Dräeger tube, H₂S 100/a, 100 to 2000 mg/L, (0-120 ppm) turns from white to brownish-black. The high-range Dräeger tube, H₂S 0.2%/a, 0.2% to 7.0%, (60-4080 ppm) turns from pale blue to jet-black.

Carbonates

Total soluble carbonates include CO₂ and the carbonate (CO₃^2-) and bicarbonate (HCO₃^-) ions. Drilling fluid filtrate is acidified in a Garrett Gas Train, converting all carbonates to CO₂, which is then evolved by bubbling an inert carrier gas through the sample. The gas train separates the gas from the liquid. The gas stream is collected in a 1 liter gas bag (to allow CO₂ to mix uniformly) and subsequently drawn through a Dräeger tube at a fixed flow rate. The Dräeger tube responds to CO₂ by progressively staining purple along its length. A reaction between CO₂ and a hydrazine chemical causes a crystal violet indicator to turn purple. The stain length is proportional to the total carbonate concentration in the filtrate.