摘要
在鄂尔多斯盆地中、东部,奥陶系顶部风化壳是主要含气层。这个含气层的孔、洞、缝网络系统在榆林—绥德一带遭到以碳酸盐为主的自生矿物的充填胶结,实际上变成致密遮挡带。遮挡带以西向着中部古隆起带东侧则形成具有工业价值的天然气藏。这个遮挡带在缺少其他有效圈闭的条件下,是能够形成天然气藏的基本要素之一。遮挡带的形成,与覆盖在奥陶系风化壳上的石炭系水具有向下侵入的水文地质条件和历史有密切关系。在石炭系成岩过程中,含盐丰富和高度变质的地下水,逐渐向下侵入奥陶系风化壳并发生盐分的析出作用,使风化壳致密化程度大大提高。风化壳致密化程度与提供水量多寡有关的石炭系厚度成正比例。遮挡带的前缘大约是石炭系厚度90m 的地带。
The weathering crust on the top of Ordovician is the main gas-bearing stratum in the central and eastern part of Ordos basin.The porous network system consisting of pores,vugs,and fractures in the stratum is filled and cemented by authigenic minerals dominated by carbonate in Yulin and Sui- de,Shanxi province.As a matter of fact,it becomes a barrier belt.On the west of the barrier belt there are some commercial gas pools to the east of the central paleolift of Ordos basin.The barrier belt is one of the basic key factors to form gas pools where other effective traps do not exist.The for- mation of the barrier belt is mainly related to the carboniferous water whi- ch lay in the Ordovician weathering crust and has down-intrusire hydroge- ologic condition in history.During diagenesis of the carboniferous,the rich- salt and high-metamorphic groudwater gradually intrudes down into the Or- dovician weathering crust and salt separation occurs.In this way,weathe- ring crust was filled.Filling of the weathering crust depends on the amount of water provided and thickness of the carboniferous.The thickness of car- boniferous in front of the barrier belt is about 90 meters.
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
1992年第2期29-35,共7页
Petroleum Exploration and Development
