Process for quantifying the pyritic sulfur and the organic sulfur of a rock sample

Process for quantifying the pyritic sulfur in a sedimentary rock sample, in which at least the following steps are applied:

• A. the sample is heated in an inert atmosphere, between a first temperature of between 80° C. and 320° C. and a second temperature of between 600° C. and 700° C., while following a first temperature sequence, and an amount of hydrocarbon-based compounds, an amount of CO and an amount of CO2 released during the first temperature sequence are continuously measured;
• B. at least one portion of the effluents resulting from the heating of the sample in an inert atmosphere is continuously oxidized, an amount of SO2 released by the oxidation of the effluents as a function of the time of the heating in an inert atmosphere is continuously measured, and at least one pyrolysis pyritic sulfur content SPyrolPyrit is determined from the amount of SO2;
• C. the residue of the sample resulting from the heating in an inert atmosphere is heated in an oxidizing atmosphere between a third temperature of between 280° C. and 320° C. and a fourth temperature of greater than or equal to 800° C., while following a second temperature sequence, and an amount of CO and an amount of CO2 released during the second temperature sequence are continuously measured;
• wherein at least one pyritic sulfur content SPyrit contained in the sample is determined on the basis of a formula of the type:
• S
• Pyrit
• =
• S
• pyrol
• Pyrit
• *
• (
• 1
• +
• β
• 1
• -
• β
• +
• γ
• 1
• -
• γ
• )
• α
• wherein α is a parameter representing a proportion of the pyrolysis pyritic sulfur relative to the total sulfur, β is a parameter representing an effect of the mineral matrix on the proportion, and γ is a parameter representing an effect of the organic matrix on the proportion, the values of the parameters α and β being predetermined, and the parameter γ being determined from a formula of the type:
• γ=ƒ(OI,HI)
• wherein ƒ is a function of at least one oxygen index OI and of a hydrogen index HI, the hydrogen index HI being a function at least of the amount of hydrocarbon-based compounds measured during the heating in an inert atmosphere and the amounts of CO and of CO2 measured during the first and second temperature sequences, and the oxygen index OI being a function at least of the amounts of CO and of CO2 measured during the first and second temperature sequences.