摘要
百色盆地东部坳陷古近系那读组的那一段上亚段和下亚段以及那二段广泛发育厚度很大的暗色泥岩 ,累计厚度可达 2 0 0～ 10 0 0m。在东部坳陷的绝大部分地区三段地层暗色泥岩的有机碳含量都在 1 0 %以上 ,是好的烃源岩。三套高效源岩的干酪根均以ⅡA型为主 ,次为ⅡB型和Ⅲ型 ,干酪根类型分布受控于沉积环境。那一段泥岩的Ro 值为 0 4 %～ 0 6 5 % ,处于未成熟—低成熟阶段 ;那二段在较深部位的Ro 值为 0 7%～ 0 8%或更高 ,处于成熟阶段的早期。该坳陷的暗色泥岩厚度高值区、半深湖区、有机碳含量高值区、Ro 高值区是一致的 ;沉积中心、沉降中心与生烃中心吻合。那二段成熟度相对较高 ,已达到成熟阶段早期 ,源岩厚度、沉积环境、有机质丰度和类型等也比较有利 ,因此 ,那二段应是本区的最主要的高效烃源岩。田东沉积区面积较大、泥岩厚度较大、半深湖区范围较大、有机碳含量较高、有机质类型较好、有机质的成熟度也相对较高 ,因此 ,田东沉积区比田阳沉积区更具有生、排烃的潜力。
Dark mudstones are widely distributed in the Upper and Lower Sections of Members 1 and 2 of Nadu Formation of Paleogene in the Eastern Depression of the Baise Basin,with an accumulative thickness of 200～1 000 m. The organic carbon content of these three sets of dark mudstones is more than 1.0% in most areas of the Eastern Depression,indicating that they are good source rocks. The kerogen of these three sets of effective source rocks is mainly type Ⅱ A ,and types Ⅱ B and Ⅲ come to the second. The distribution of the kerogen type was controlled by sedimentary environment. R o values of the mudstones in the Member 1 of Nadu Formation are 0.4%～0.65%,indicating that the organic matter was at immature to low mature stage,while those of the Member 2 of Nadu Formation at a deep position are 0.7%～0.8% or even higher,showing that the organic matter was at the early period of mature stage. The range of thicker dark mudstones in the depression is identical with the environment of semi-deep lake and the areas with higher organic carbon and R o values,i.e. the depositional center and the subsiding center of the basin are identical with the hydrocarbon generation center. The maturity of the Member 2 of Nadu Formation is relatively high,reaching the early period of mature stage,and the source rock thickness,the sedimentary environment,and the organic abundance and type of this member are also favorable. Therefore,the Member 2 of Nadu Formation should be the most effective source rock in this area. The Tiandong sedimentary district,which has a larger area,a larger thickness of mudstone,a larger range of semi-deep lacustrine environment,a higher organic carbon content,better organic matter type and higher maturity,has a greater potential of hydrocarbon generation and expulsion than the Tianyang sedimentary district.
出处
《古地理学报》
CAS
CSCD
2005年第1期113-124,共12页
Journal of Palaeogeography：Chinese Edition
基金
中国石油化工集团公司科技攻关项目"百色盆地成烃成藏基础理论研究"中的部分成果
