渤海海域渤中地区烃源岩封闭金管热解模拟生烃实验研究

Gold tube pyrolysis study of source rock hydrocarbon generation in Bozhong area,offshore Bohai Bay Basin

选取渤海海域渤中地区沙南凹陷沙三段、沙一段和东三段烃源岩各1个样品,秦南凹陷沙三段烃源岩2个样品,进行封闭金管加水热解实验。烃源岩样品为湖相泥岩,有机质丰度高,干酪根类型为Ⅰ型,且处于低熟阶段。烃源岩矿物组成以黏土矿物为主,方解石、石英和长石也占有相当的比重。热解过程涵盖了主要的生油阶段,沙三段、沙一段和东三段烃源岩平均生烃活化能集中分布在219~222 k J/mol,同一凹陷不同层系、不同凹陷同一层系差别不大,但黏土矿物含量较低和方解石含量较高的样品平均活化能略偏高。封闭热解生烃高峰C_(14+)液态烃产物碳同位素相比原岩沥青"A"碳同位素增重幅度可达11.3%,应用低熟源岩沥青"A"碳同位素进行油源对比时须谨慎。残余固体总有机碳损失可达48%,对原本有机质丰度高和类型好、现处于高演化阶段的烃源岩评价时,有必要进行有机质丰度和类型的恢复。

Sealed gold tube pyrolysis was carried out for 3 source rock samples from the third （E2s^3） and first （E3s^1） members of Shahejie Formation, and the third （E3d^3） member of Dongying Formation in the Shanan Sag, and 2 source rock samples from the E2s3 in the Qinnan Sag in Bozhong area. These samples are lacustrine shale with a high organic matter content and low maturity, and contain type I kerogen. Minerals in the source rock samples are mainly clay minerals and contain a significant amount of calcite, quartz and feldspar. The gold tube pyrolysis experiments focus on liquid hydrocarbon generation. The mean hydrocarbon generation kinetics of E2s^3, E3s^1 and E3d^3 source rock samples range between 219 and 222 kJ/mol, and the kinetics of all samples have a concentrated distribution. Samples from same sag but different intervals, and samples from different sags but same interval have no significant difference, but the samples with a relatively low content of clay minerals and a high content of calcite have a relatively higher mean hydrocarbon activation energy. Carbon isotopes of C14＋ liquid products during peak hydrocarbon generation can be 11.3% heavier than extracts from unpyrolyzed samples, and oil-source correlation with extracts from low maturity source rocks must consider this. TOC loss of residual solids can reach up to 48%. It is necessary to restore organic matter abundance and kerogen type when evaluating high maturity source rocks with a high organic abundance and favorable organic type.