内蒙古西乌旗地区下二叠统寿山沟组烃源岩有机地球化学特征

近些年二连盆地及外围地区石炭—二叠系油气研究工作表明该区具有很大的勘探潜力，西乌旗下二叠统寿山沟组为该区油气勘探的重要目的层之一。为了更准确、深入地认识寿山沟组烃源岩的品质，本文针对寿山沟组烃源岩样品进行有机地球化学特征方面的研究。通过总有机碳（TOC）测试、氯仿沥青及族组分抽提分离、生油岩热解分析、饱和烃GC-MS测试手段重点对烃源岩进行有机质丰度、成熟度及类型评价，并根据有机分子地球化学特征判识生烃母质来源及其沉积环境。研究结果表明：样品总有机碳含量（TOC）均值为1.01%，氯仿沥青“A”含量均值为0.23%，生烃潜量PG（S₁+S₂）均值为0.05×10^-3，综合判识烃源岩有机质丰度为“中等—较好”级别；样品Ro值较高，介于1.67%~4.36%，结合Ts/（Ts+Tm）值与C₂₉甾烷异构化参数特征综合判断有机质成熟度达“高成熟—过成熟”阶段；生物标志物分析结果表明烃源岩的生烃母质以低等浮游生物、菌藻类为主，陆生高等植物为辅，有机质类型为Ⅱ₁、Ⅱ₂型；古水体盐度较高，有机质保存于还原性条件。综合有机质丰度、类型、成熟度、保存条件各项参数认为西乌旗地区寿山沟组烃源岩可达“中等—较好”级别，可为研究区油气资源富集提供气源。

Organic geochemical characteristics of source rocks of Lower Permian Shoushangou Formation in Xiwuqi area,Inner Mongolia

The investigation of Carboniferous-Permian oil and gas in the Erlian Basin and its environs in recent years has revealed that this region has excellent exploration potential. One of the key target strata for oil and gas exploration in this region is the Lower Permian Shoushangou Formation in Xiwuqi. This research examines the organic geochemical properties of source rock samples from the Shoushangou Formation in order to more fully and properly evaluate the quality of those rocks. The abundance, maturity, and type of the source rock's organic matter were assessed using the Total Organic Carbon (TOC) test, chloroform bitumen and group component extraction and separation, source rock pyrolysis analysis, and saturated hydrocarbon GC-MS test, and the source of the hydrocarbon-generating parent material and its sedimentary environment were identified using organic molecular geochemical characteristics. The findings indicate that: TOC content is on average 1.01%, chloroform bitumen ("A") content is on average 0.23%, and hydrocarbon generation potential (S1+S2) content is on average 0.05×10-3. The source rock's level of organic matter richness is "medium-better". The sample has a high Ro value, which ranges from 1.67% to 4.36%. It is determined that the maturity of organic matter has reached the stage of "high maturity-over maturity" when taken into account with the Ts/(Ts+Tm)value and the characteristics of C29 sterane isomerization parameters. The results of biomarker analysis reveal that low plankton, bacteria, and algae, along with higher terrestrial plants, are the primary hydrocarbon- producing parent materials of source rocks, and the organic matter categories are Ⅱ1 and Ⅱ2. High salinity and lowering conditions have preserved the organic stuff in the old water. Based on the parameters of organic matter abundance, type, maturity and preservation conditions, it is considered that the source rocks of Shoushangou Formation in Xiwuqi area can reach the 'medium-good' level, which can provide gas source for the enrichment of oil and gas resources in the study area.