A method of developing an underground reservoir of hydrocarbons containing organosulfur compounds, characterized in that it comprises: A. determining an amount of hydrogen sulfide (H 2 S) produced over time by an aquathermolysis phenomenon induced by a thermal process such as steam injection into said reservoir, from a gridded representation of said reservoir, from experimental measurements performed on at least one sample of said hydrocarbons and/or a rock sample from said reservoir, by carrying out the following steps: i. constructing an elementary reaction scheme representative of a material balance for the element sulfur from at least one compositional representation of the hydrocarbons, said representation describing said hydrocarbons in different pseudo-constituents, of at least one solid pseudo-constituent, at least one H 2 S constituent and pseudo-stoichiometric coefficients relative to said pseudo-constituents and constituents; ii. constructing a kinetic model from at least one reaction system simulating said aquathermolysis phenomenon, said reaction scheme, of atomic balances relative to each one of said reactions of said reaction system, said balances relating at least to the sulfur, carbon and hydrogen atoms, and said reaction system being a function of stoichiometric coefficients relative to at least said pseudo-constituents and constituents; iii. constructing a thermodynamic model of the pseudo-constituents of said compositional representation; iv. calibrating a thermo-kinetic model consisting of said kinetic model and of said thermodynamic model, from said experimental measurements; v. determining said amount of hydrogen sulfide (H 2 S) produced by performing a compositional reservoir simulation by means of a compositional and reactive thermal simulator, said simulator implementing said thermo-kinetic model, and by means of said gridded representation; B. determining development conditions for said reservoir as a function of said amount of hydrogen sulfide; C. producing said hydrocarbons by applying said development conditions. A. determining an amount of hydrogen sulfide (H 2 S) produced over time by an aquathermolysis phenomenon induced by a thermal process such as steam injection into said reservoir, from a gridded representation of said reservoir, from experimental measurements performed on at least one sample of said hydrocarbons and/or a rock sample from said reservoir, by carrying out the following steps: i. constructing an elementary reaction scheme representative of a material balance for the element sulfur from at least one compositional representation of the hydrocarbons, said representation describing said hydrocarbons in different pseudo-constituents, of at least one solid pseudo-constituent, at least one H 2 S constituent and pseudo-stoichiometric coefficients relative to said pseudo-constituents and constituents; ii. constructing a kinetic model from at least one reaction system simulating said aquathermolysis phenomenon, said reaction scheme, of atomic balances relative to each one of said reactions of said reaction system, said balances relating at least to the sulfur, carbon and hydrogen atoms, and said reaction system being a function of stoichiometric coefficients relative to at least said pseudo-constituents and constituents; iii. constructing a thermodynamic model of the pseudo-constituents of said compositional representation; iv. calibrating a thermo-kinetic model consisting of said kinetic model and of said thermodynamic model, from said experimental measurements; v. determining said amount of hydrogen sulfide (H 2 S) produced by performing a compositional reservoir simulation by means of a compositional and reactive thermal simulator, said simulator implementing said thermo-kinetic model, and by means of said gridded representation; i. constructing an elementary reaction scheme representative of a material balance for the element sulfur from at least one compositional representation of the hydrocarbons, said representation describing said hydrocarbons in different pseudo-constituents, of at least one solid pseudo-constituent, at least one H 2 S constituent and pseudo-stoichiometric coefficients relative to said pseudo-constituents and constituents; ii. constructing a kinetic model from at least one reaction system simulating said aquathermolysis phenomenon, said reaction scheme, of atomic balances relative to each one of said reactions of said reaction system, said balances relating at least to the sulfur, carbon and hydrogen atoms, and said reaction system being a function of stoichiometric coefficients relative to at least said pseudo-constituents and constituents; iii. constructing a thermodynamic model of the pseudo-constituents of said compositional representation; iv. calibrating a thermo-kinetic model consisting of said kinetic model and of said thermodynamic model, from said experimental measurements; v. determining said amount of hydrogen sulfide (H 2 S) produced by performing a compositional reservoir simulation by means of a compositional and reactive thermal simulator, said simulator implementing said thermo-kinetic model, and by means of said gridded representation; B. determining development conditions for said reservoir as a function of said amount of hydrogen sulfide; C. producing said hydrocarbons by applying said development conditions.