银额盆地艾西凹陷烃源岩地球化学特征及资源潜力

为明确银额盆地艾西凹陷烃源岩条件和油气资源潜力，基于2口探井泥岩样品的测试分析资料，对烃源岩开展系统的评价研究，对有效烃源岩进行预测，在此基础上分析油气资源潜力。艾西凹陷潜在烃源岩为发育于白垩系乌兰苏海组(K₂w)、银根组(K₁y)、苏红图组(K₁s)、巴音戈壁组三段(K₁b³)、二段(K₁b²)和一段(K₁b¹)的泥岩，其中K₁b³、K₁b²和K₁b¹泥岩有机质丰度最高，其有机质类型均偏腐殖型(Ⅱ型—Ⅲ型)，成熟度均达到成熟热演化阶段。元素地球化学和生物标志化合物资料表明，烃源岩沉积期的古气候温暖湿润，沉积水体主要为淡水，陆源高等植物的生源贡献占优势。有利于有机质富集的沉积环境为盐度较高、还原性较强的环境，高生产力是有机质富集的主要控制因素。厘定了研究区有效烃源岩的TOC含量下限值为0.85%，有效烃源岩主要发育于K₁b³、K₁b²和K₁b¹，它们在南凹漕带、中凹漕带、北凹漕带和西凹漕带具有一定面积的分布。估算出研究区的油气总资源量为5 091.05×10⁴ t，结合活跃的油气显示证据，认为研究区具有较好的油气勘探潜力。

Geochemical characteristics and resource potential of source rocks in Aixi Sag,Yingen-Ejinaqi Basin

In order to clarify the source rock conditions and oil/gas potential of the Aixi Sag in the Yingen-Ejinaqi Basin, based on the analytical results of mudstone samples from two exploratory wells, a systematic evaluation of the source rocks was carried out in this paper, and the effective source rocks were supposed. The potential source rocks in the study area are mudstones developed in Cretaceous Wulansuhai Formation (K₂w), Yingen Formation (K₁y), Suhongtu Formation (K₁s), and the third (K₁b3), second (K₁b2) and first member (K₁b1) of Bayingebi Formation, among which the K₁b3, K₁b2 and K₁b1 mudstones have the highest abundance of organic matter with the kerogen types of Ⅱ-Ⅲ at mature stages of thermal evolution. Elemental geochemical and biomarker data show that the paleoclimate during the deposition of source rocks was warm and humid, the sedimentary water was mainly fresh water, and the contribution of terrestrial organic matter was dominant. The favorite sedimentary paleoenvironment conducive to organic matter enrichment is high salinity and strong reducibility, and high productivity is the main controlling factor for the enrichment of organic matter. The lowest limit of TOC content of effective source rocks is supposed to be 0.85%, and the effective source rocks are mainly developed in K₁b3, K₁b2 and K₁b1. They are mainly distributed in considerable areas in the southern, central, northern and western subsags. The total oil and gas resources in the study area are estimated to be around 5 091.05×104 t. Combined with the evidence of active oil and gas display, it is concluded that the study area has good oil and gas exploration potential.