利用油砂和烃源岩抽提沥青质的稀土元素、过渡族金属元素判识油源——以鄂尔多斯盆地延安地区延长组下组合为例

The Oil Source Analysis of Rare Earth Elements and Transition Group Metal Elements Extracted from Asphaltenes by Oil Sands and Hydrocarbon Source Rocks—A Case Study of the Lower Assemblage of Yanchang Formation in Yan’an Region, Ordos Basin

摘要: 针对鄂尔多斯盆地延安地区延长组长8~长10油层组受多种油源供给，常规烃源岩生物标志化合物难以区分不同油层的油源的问题。本文利用油砂和烃源岩抽提沥青质的稀土元素、过渡族金属元素丰度配分模式，结合饱和烃的C27、C28、C29重排甾烷，对研究区长8~长10油层组的油源进行了综合判识。认为研究区长8~长10油源总体上为长7湖盆中心优质烃源岩和研究区长9烃源岩的混源，而研究区长7暗色泥岩和长10烃源岩基本上没有贡献，吴起、顺宁、西河口3个地区以及不同的层位的油源存在一定的差异性。研究表明，油砂和烃源岩抽提沥青质的稀土元素、过渡族金属元素丰度配分模式对研究区长8~长10油层组油源判识具有良好的效果，该方法是对湖相油源判识的一种有效补充。

Abstract: The Chang-8~Chang-10 oil reservoirs of Yanchang formation are supplied by multiple oil sources in Yan’an area of Ordos Basin. It is difficult to distinguish the oil sources of different reservoirs by conventional source rock biomarkers. The paper analyzes comprehensively the oil resource of Chang-8~Chang-10 oil-bearing beds in study region by the abundance partitioning model of rare earth elements and transition group metal elements extracted from asphaltenes by oil sands and hydrocarbon source rocks, and by combining with the rearrangement of C27, C28 and C29. It is considered that the oil sources of Chang-8~Chang-10 in the study region are generally a mixture of the high-quality source rocks in the center of the Chang-7 lake basin and the source rocks of Chang-9 in the study area, while the dark mudstone of Chang-7 and the source rocks of Chang-10 in the study region have almost no contribution, and the oil sources of different formation of Wuqi, Shunning and Xihekou in the study region have difference. The result reflects that the abundance partitioning model of rare earth elements and transition group metal elements extracted from asphaltenes by oil sands and hydrocarbon source rocks has good effect on Chang-8~Chang-10 formation. The mean is an effective supplement of lacustrine oil source.