辽河油田杜84块H2S成因探讨

辽河油田杜84块超稠油由蒸汽吞吐转为蒸汽辅助重力泄油（SAGD）开发后，产生了较高浓度的H₂S，导致脱硫设施投入和油气处理成本增加。通过原油、伴生气、地层水和储层矿物地球化学测试分析，H₂S产量与原油含硫量、地层水SO₄2-浓度无明显相关性，而与储层中黄铁矿含量一致性强，黄铁矿中的硫属于生物来源，同位素范围与原油基本一致，起源于原油稠化阶段，大量形成于稠油热采阶段。高温高压热模拟实验表明，注蒸汽热力采油过程中，除含硫有机质热裂解（TDS）和硫酸盐热化学还原反应（TSR）外，黄铁矿氧化分解也是H₂S形成途径之一，当注入低矿化度蒸汽对地层水稀释后，SO₄2-浓度下降，黄铁矿分解是H₂S的主要生成途径，H₂S的生成和分布受控于油藏地质条件、开发方式、开发时间和受热温度。 

Genesis of hydrogen sulfide in Du 84 block,Liaohe Oilfield

During the thermal recovery of extra heavy oil in the Liaohe Oilfield, the concentration of H₂S increased, which results in the increased cost of the desulfurization facility and oil-and-gas treatment. Crude oil, associated gas, formation water and reservoir minerals were analyzed and the H₂S production had no significant correlation with the sulfur content in the crude oil and the SO₄2- concentration in the formation water, but had a good covariance with the pyrite content in reservoir. The sulfur in pyrite had biological source, and its isotopic range was basically consistent with that of crude oil, which originates in the thickening stage of crude oil and forms in large quantities in the thermal recovery stage of heavy oil. Except for the thermal decomposition of organic sulfur compounds (TDS) and thermochemical sulfate reduction (TSR), the thermal simulation experiment shows that the decomposition of pyrite is also one of the ways to produce H₂S in the process of steam thermal recovery. When injected, lower salinity steam dilutes the formation water and pyrite decomposition becomes the main source of H₂S. The production concentration of hydrogen sulfide was controlled by reservoir geology, the thermal recovery method, heating time and temperature.