TSR对气态烃组分及碳同位素组成的影响——高温高压模拟实验的证据

选用高含硫原油、Ⅱ型干酪根、Ⅲ型干酪根以及硫酸镁作为反应物,设计了3组共6个反应体系,以对比发生硫酸盐热还原作用(TSR)与否对烃类组分及碳同位素的影响。模拟实验利用黄金管—高压釜限定系统完成,6个反应体系具有完全相同的反应温度和压力,反应结果具有可对比性。模拟实验结果证实:①TSR反应导致气态产物中H₂S和CO₂含量的明显增加;②TSR反应导致气态天然气组分变干,即碳数越多的气态烃越容易发生TSR反应,甲烷很难作为反应物参与TSR反应;③TSR反应导致气态烃碳同位素变重,而CO₂碳同位素变轻;④TSR导致甲烷碳同位素变重最多,乙烷、丙烷碳同位素变重相对较小,即δ13C₂与δ13C₁差值变小。TSR反应导致的天然气组分及碳同位素的变化影响了油气源对比的经验公式及判断指标,因此在高含硫天然气区进行气源对比时应考虑TSR的影响。 

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.