Changes in Sulfur Content and Isotopic Ratios of Sulfur during Petroleum Maturation--Study of Big Horn Basin Paleozoic Oils
Changes in Sulfur Content and Isotopic Ratios of Sulfur during Petroleum Maturation--Study of Big Horn Basin Paleozoic Oils
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DOI：
10.1306/83d91b9b-16c7-11d7-8645000102c1865d
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发表时间：
1974-11
期刊：
影响因子：
3.5
通讯作者：
W. L. Orr
中科院分区：
文献类型：
--
作者：
W. L. Orr
使用大角盆地（怀俄明州）古生代石油作为“单一来源”石油的例子，研究了硫含量和硫同位素比随“热成熟”的变化，这些石油由于热历史的变化而达到了不同的成熟阶段。随着成熟度的增加，API°、GOR、S/N、^dgrC13 和 ^dgrS34 均增加，而百分比 S 和百分比 N 减少。除了 ^dgrS34 和 S/N 的增加外，这些变化通常被认为是热成熟过程的典型变化。浅层储层中微生物硫酸盐还原产生的低浓度硫化氢在ΔdgrS34 中变化，并且通常不会改变伴生油的ΔdgrS34。由于在低温和低 H2S 压力下 H2S 和油之间的反应可以忽略不计，因此同位素无关的 H2S 和有机硫可能会保留很长时间。这项研究的主要新结论是，存在硫酸盐的高温储层（超过 80-120°C）的热成熟可能涉及同位素分馏可忽略不计的非微生物硫酸盐还原，产生与储层硫酸盐同位素组成几乎相同的还原硫物质。在这种情况下，油的硫化和脱硫在动力学控制过程中竞争，导致同位素交换。油中H2S和有机硫的^dgrS34向储层硫酸盐的^dgrS34变化。 H2S 的交换比石油更快。具有均质 ^dgrS34 分布、沸点和化合物类型的初始油变得异质；低沸点馏分比高沸点馏分更快地接近储层硫酸盐值。信噪比随熟化的大幅增加归因于通过竞争的硫化和脱硫过程将硫百分比维持在显着水平，而氮百分比继续下降。高温硫酸盐还原机理被认为是H2S和SO4=反应生成单质硫和多硫化物，它们快速反应氧化和脱氢有机化合物并将硫分配在油和H2S之间。在这种情况下，可能会积聚高浓度的 H2S，并且油或凝析油可能会产生异常高浓度的硫醇。 H2S是一种催化剂，也是反应的产物；因此，该过程可能是自催化的。
Changes in sulfur content and sulfur-isotope ratios with "thermal maturation" have been studied using Big Horn basin (Wyoming) Paleozoic oils as examples of "single source" oils which have attained different stages of maturity as a result of variations in thermal history. With increasing maturity, API°, GOR, S/N, ^dgrC13, and ^dgrS34 all increase, whereas percentage S and percentage N decrease. Except for the increase in ^dgrS34 and S/N, these changes generally are recognized as typical of the thermal-maturation process. Hydrogen sulfide produced in low concentrations by microbial sulfate reduction in shallow reservoirs varies in ^dgrS34 and generally does not appear to change ^dgrS34 of associated oil. Isotopically unrelated H2S and organic sulfur may remain for long times because of negligible reaction between H2S and oil at low temperatures and low H2S pressures. The major new conclusion from this study is that thermal maturation in high-temperature reservoirs (more than 80-120°C) with sulfate present may involve nonmicrobial sulfate reduction with a negligible isotopic fractionation, producing reduced sulfur species with nearly the same isotopic composition as the reservoir sulfate. In this case, sulfurization and desulfurization of oil compete in kinetically controlled processes resulting in isotopic exchange. The ^dgrS34 of H2S and organic sulfur in oils change toward that of reservoir sulfate. Exchange is faster for H2S than for oil. Initial oils with a homogeneous ^dgrS34 distribution with boiling point and compound type become heterogeneous; the lower boiling fractions approach reservoir s lfate values faster than high-boiling fractions. The large increase in S/N ratio with maturation is attributed to percent S being maintained at a significant level by competing sulfurization and desulfurization processes, whereas percent N continues to decrease. The mechanism for high-temperature sulfate reduction is proposed to be the reaction of H2S and SO4= to produce elemental sulfur and polysulfides, which react rapidly to oxidize and dehydrogenate organic compounds and distribute the sulfur between oil and H2S. High concentrations of H2S may accumulate in this case, and oils or condensates may develop abnormally high concentrations of thiols. H2S is a catalyst as well as a product of the reaction; the process, therefore, may be autocatalytic.