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通过烃源岩沉积特征及地球化学实验数据分析,对鄂尔多斯盆地西南缘中上奥陶统烃源岩分布和生烃潜力进行了系统评价。鄂尔多斯盆地西南缘奥陶系烃源岩主要发育在中上奥陶统克里摩里组和乌拉力克组,呈“L”字形围绕中央古隆起分布;它们为一套厚度较大的深水相泥页岩和含泥灰岩沉积。烃源岩生烃母质类型以Ⅰ型干酪根为主,Ⅱ1型次之。有机碳丰度在不同层位不同岩性均有差别;从层位上来看,乌拉力克组和克里摩里组烃源岩TOC平均值分别为0.58%和0.50%,达到中等烃源岩生烃标准;从岩性上来看,泥质烃源岩有机质丰度高于含泥碳酸盐岩。除沙井子地区为低成熟阶段外,鄂尔多斯盆地中上奥陶统海相烃源岩热成熟度均处于高成熟—过成熟阶段。鄂尔多斯盆地中上奥陶统海相烃源岩生烃量合计达48×1012 m3,总资源量为2.3×1012 m3,西部天环北地区和南部淳化地区为2个生烃中心,是下一步勘探的重点方向。
Based on the sedimentary characteristics of source rocks and the analysis of geochemical experimental data, the distribution of middle-upper Ordovician source rocks and hydrocarbon generation potential in the southwestern margin of Ordos Basin are systematically evaluated. The Ordovician source rocks in the southwestern Ordos Basin are mainly developed in the Upper-Middle Ordovician Cremoli Formation and the Ulalik Formation and distributed in the shape of “L” from the central paleohigh. They are a set of thicker deep-water phase Shale and marl deposits. The types of hydrocarbon-bearing parent rocks are mainly type I kerogens, followed by type II1. The organic carbon abundance varies in lithology at different layers. According to the horizon, the TOC values of the source rocks in the Ulalik Formation and the Creimoli Formation are 0.58% and 0.50%, respectively, reaching the standards of hydrocarbon generation of medium source rocks In terms of lithology, the organic matter abundance of shaly source rocks is higher than that of muddy carbonate rocks. Except that the Shajingzi region is in the low maturity stage, the thermal maturation of the Middle-Upper Ordovician marine source rocks in the Ordos Basin is in the stage of high maturity-maturity. The hydrocarbon generation amount of the middle-upper Ordovician marine source rocks in the Ordos Basin totaled 48 × 1012 m3, with a total resource of 2.3 × 1012 m3. The two hydrocarbon generation centers are located in the North Tianhebei area in the west and Chunhua area in the south, which is the focus of exploration in the next step direction.