摘要
贵州奥陶—三叠纪海相沉积发育,分布广泛。这些沉积中含有丰富的牙形石和油气显示,为研究牙形石的颜色变化指标(CAI)和烃类相态之间的关系提供了良好的条件。有关贵州牙形石CAI资料曾有周希云(1980,1985,1987)、蒋武(1980)、钟端和董致中(1982)等作了零散报导。 根据A.G.Epstein等(1977)所建立的CAI系列,贵州及邻区的86个地层剖面或产地的奥陶—三叠系的牙形石颜色可分成1.5—5CAI级和4个不同的CAI值区。CAI高值或低值区分别与高或低的古地温梯度和大或小的原始埋深区相对应。 文中讨论了CAI与烃类相态之间的关系。奥陶—三叠系的CAI低值区对石油的生成和热力保存较有利,但在贵州这些地区均已暴露,不再具有石油勘探价值。CAI的中—高值区,可生成天然气,在有区域盖层的地区得以保存。在贵州,这种有利于天然气保存的地区大约还有40000km^2,它相当于贵州总面积的24％。
The Ordovician - Triassic marine sediments are well - developed and widely distributed in Guizhou. There are abundant conodonts and hydrocarbon outcrops in the sediments, thus providing an excellent condition for the study of relationship between conodont colour alteration index (CAI) and facies of hydrocarbon occurrences. The data of CAI in Guizhou were reported by Zhou Xiyun (1980, 1985, 1987), Jiang wu (1980), Zhong Duan and Dong zhizhong (1982).
According to the sequence of CAI established by Epstein A. G. and others (1977) , the Ordovi-cian -Triassic conodont colours from 86 stratigraphic sections or places in Guizhou and adjacent areas may be divided into the grades of CAI from 1. 5 to 5 and 4 different value areas of CAI. The higher or lower value areas of CAI correspond to the higher or lower paleogeothermal gradients and to the larger or less primitive depths of burial respectively.
The corresponding relations between CAI and facies of Hydrocarbon occurrences are discribed in this paper. The lower value areas of CAI in Ordovician -Triassic systems are more beneficial to petroleum formation and heat - retaining, but these areas are outcropped and have little value for exploring oil in Guizhou. In the midium - high CAI areas,the gascan be formed and preserved where there is a condition of regional covering strata. These areas of beneficial preservable gas are of about 40000 km2, corresponding to 24% of the total area of Guizhou.
出处
《贵州地质》
1990年第4期361-372,共12页
Guizhou Geology
