鄂尔多斯盆地伊盟隆起上古生界烃源岩地球化学特征

烃源岩是石油和天然气生成的物质基础,决定了勘探区块的潜在资源量,具有重要的研究价值。对鄂尔多斯盆地伊盟隆起上古生界烃源岩进行岩性、厚度以及地球化学分析,结果表明:上古生界烃源岩岩性主要为泥岩、炭质泥岩和煤层,上古生界暗色泥岩总厚度一般为10~50 m;平面上具有南厚北薄、东厚西薄、局部发育的特征;太原组和山西组炭质泥岩和煤层有机质丰度较高;干酪根以Ⅲ型为主,其次为Ⅱ型;原始有机质形成于弱氧化环境;上古生界烃源岩Ro值介于0.6%~1.8%之间,已经进入成熟-高成熟阶段,且南部生气强度大。其研究结果可以为伊盟隆起区上古生界的油气资源评估提供依据。

GEOCHEMISTRY AND EVALUATION OF UPPER PALEOZOIC SOURCE ROCK ON YIMENG UPLIFT,ORDOS BASIN

Source rock founds the basis for hydrocarbon generation and is of significance to determination of the resource potential in the exploration area. This paper is devoted to the lithology, thickness and geochemical characteristics of the Upper Paleozoic source rock in the Yimeng Uplift belonging to Ordos Basin. The Upper Paleozoic source rocks in the Yimeng Uplift are mainly consisting of dark mudstone, carbonaceous mudstone and coal of the Taiyuan and Shanxi Formations. According to the statistics, the total thickness of the Upper Paleozoic dark mudstone in northern Ordos Basin ranges from 10 to 50m while the total thickness of coal is between 2 and 25m. Hydrocarbon source rocks in the southern and eastern parts of the Yimeng Uplift are thicker than those in the northern and western parts, and the quality of source rocks seems better in some depressions than that in other areas. Carbonaceous mudstone and coals in the Taiyuan and Shanxi Formations are relatively high in organic matters, dominated by the Type Ⅲ of Kerogen followed by the type Ⅱ. The original organic matter is supposed to be deposited in an aerobic environment. Ro value ranges from 0.6% to 1.8%, suggesting that the source rock has entered a matured or high matured stage. The amount of gas generated by the Upper Paleozoic source rock in the southern part is larger than that produced in the northern part of the Yimeng Uplift. The results of the study may provide a basis for hydrocarbon evaluation of the Upper Paleozoic in the Yimeng Uplift.