Influences of TSR on gaseous hydrocarbon components and carbon isotopes：revelations from high-temperature and high-pressure simulation experiments

Crude oil rich in sulfur,kerogen of types Ⅱ and Ⅲ and magnesium sulfate were tested in 6 reaction systems(divided into 3 groups) so as to study the influences of thermochemical sulfate reduction(TSR) on gaseous hydrocarbon components and carbon isotopes.The tests were made in gold tube-autoclave system.The above-mentioned 6 reaction systems had the same temperature and pressure;hence their results were comparable.The modeling experiments have proved that: 1)TSR leads to the obvious increase of H₂S and CO₂ yields;2)TSR makes gaseous hydrocarbon become dryer,that is,the C₂₊ series are easier to react in TSR while CH₄ seldom participates in TSR;3)TSR makes the carbon isotopes of gaseous hydrocarbon become heavier and that of CO₂ become lighter;4) TSR makes much more obvious change of carbon isotopes in methane than in ethane and propane,that is,the value of δC₂-δC₁ decreases.The changes of gaseous hydrocarbon components and carbon isotopes caused by TSR influence the index and empirical formula of gas-source rock correlation,so the influences of TSR should be taken into consideration in gas-source rock correlation of natural gas rich in sulfur.