Sulfur and amorphous dithiazine measurement
The disclosure describes a method to indirectly measure the amount of elemental sulfur or amorphous dithiazine in a reservoir sample by converting them to H 2 S gas. The H 2 S is captured via caustic cyanide solution and quantified by analytical methods and correspond to the concentration of elemental sulfur or amorphous dithiazine. The method has particular applicability to determine where best to drill and avoid locations of high sulfur.
1 . A method of producing oil, said method comprising:
a) obtaining a plurality of samples, each sample from a known location in an oil reservoir and containing MEA or a triazine, or MEA or a triazine being added thereto;
b) optionally analyzing each of said plurality of samples or portion thereof to determine a first amount of H 2 S remaining unreacted with said MEA or triazine after step a);
c) analyzing each of said plurality of samples or portion thereof to determine an amount of dithiazine and correlating said amount of dithiazine to a second amount of H 2 S;
d) analyzing each of said plurality of samples or portion thereof for an amount of amorphous dithiazine (a-DTZ) by treatment with a reductive mercaptan solution to convert a-DZT to H 2 S and measuring a third amount of H 2 S and correlating said third amount of H 2 S to said amount of a-DTZ in said plurality of samples;
e) calculating a total amount of H 2 S in a each sample from a each said known location by adding said optional first amount of H 2 S from step b), said second amount of H 2 S from step c), and said third amount of H 2 S from step d), thereby determining one or more highest H 2 S content location(s) in said reservoir and one or more sweeter content location(s);
f) producing oil from said one or more sweeter content location(s) as determined in step e); and
g) wherein said produced oil has less H 2 S than a method of producing oil from said reservoir without steps a) through f).
2 . The method of claim 1 , wherein plurality of samples are drilling mud samples obtained while drilling an oil well or a test well.
3 . The method of claim 1 , wherein said plurality of samples are core samples.
4 . The method of claim 1 , wherein said reductive mercaptan solution comprises a mercaptan, an amine and an alcohol.
5 . The method of claim 1 , wherein said optional first, said second, and said third amounts of H 2 S are measured by a reaction with caustic cyanide and determining an amount of thiocyanate or isothiocyanate produced.
6 . The method of claim 5 , wherein said amount of thiocyanate or isothiocyanate is determined by reaction with iron or copper plus pyridine and measuring an amount of color produced.