云南思茅盆地二叠纪层序格架与生储盖研究

The Permian sequence stratigraphic framework and source-reservoir-caprock associations in the Simao Basin,Yunnan

关键词:  二叠纪  层序格架  生储盖  思茅盆地  云南

Key words:  Permian  sequence stratigraphic framework  source-reservoir-caprock association  Simao Basin  Yunnan

摘要:

根据层序界面的特点、凝缩段的组成,思茅盆地二叠系可分为2个Ⅱ级层序、9个Ⅲ级层序。在此基础上,探讨了层序格架与油气生储盖的关系可分为2个二级层序界面为一构造侵蚀不整合层序界面,是极好的储集场所。此时西部盆地中沉积物已经变质,与生储盖关系不大;而东部地区以开阔碳酸盐台地为主,低位体系域、海侵体系域和高位体系域以形成储集层为主。第2个二级层序由海侵-高位体系域所构成。海侵体系域由龙潭组下部所组成,在普洱西部崖子以西为深水盆地(含斜坡)环境,以东为浅海环境,邻近东部古陆区为滨海环境。无论盆地或浅海,岩性以深灰—灰黑色泥岩为主,生烃性能极好。高位体系域可以分为早期高位体系域和晚期高位体系域。早期高位体系域由龙潭组上部层位组成,西为浅海相砂岩、火山岩等,可作储层;东为滨海平原,下部以深灰、灰黑色泥岩为主,是很好的生油岩,上部以砂岩为主夹火山岩,可作为储集层。晚期高位体系域西部为长兴组灰岩、白云质灰岩、白云岩,可作为储层之用。

Abstract:

Two second-order sequences and nine third-order sequences may be identified for the Permian strata in the Simao Basin,Yunnan in the light of sequence boundary and condensed sections.The first second-order sequence boundary is represented by a tectonic-erosional unconformity which may be the best locus for the preservation of oil and gas.Since the sediments in the western part of the basin have been subjected to metamorphism,they have nothing to do with the source-reservoir-caprock associations throughout the basin.In the eastern part of it,the lowstand,transgressive and highstand systems tracts on the open carbonate platform have all contributed to good sites for the formation of reservoir rocks.The second second-order sequence boundary consists of transgressive and highstand systems tracts.As for the transgressive systems tract composed of the lower horizons of the Longtan Formation,the deep-water basin slope environments appear in the areas west of Yazi in western Pu'er while the shallow-marine environments east of it,and the littoral environments near the ancient land in the east.The lithology is,without exception,dominated by dark grey-greyish black mudstones which have excellent hydrocarbon potential.The highstand systems tract may be grouped into two types:early and later types.The early highstand systems tract is made up of the upper horizons of the Longtan Formation:shallow-marine sandstones and volcanic rocks as reservoir rocks in the west,and littoral plain in the east, where the dark grey and greyish black mudstones as good source rocks occur in the lower part while in the upper part the sandstones intercalated with volcanic rocks as reservoir rocks are accentuated.In the western part of the late highstand s ystems tract,limestone,dolomitic limestone and dolostone may serve as reservoir rocks.