鄂尔多斯盆地白河区早中侏罗世沉积相及其与油气运聚的关系

白河区延安组地层平缓,构造不发育,油藏分布范围小,但产量高,针对这一特点,对研究区早中侏罗世的沉积相及其与油气运聚的关系进行了探讨。利用岩性和测井曲线特征,对沉积相、微相类型进行了识别与划分,认为白河区富县组、延10油层组为辫状河沉积体,发育河道砂坝、心滩、河漫滩和河漫沼泽等沉积微相;延9油层组为三角洲平原沉积体系,发育分流河道和分流间湾等沉积微相。同时以延长组长1、长2残余地层厚度的分布,恢复了前侏罗系的古地貌特征。研究表明,富县组的巨厚砂层是下部过剩压力的泄压口,是下部油气向延安组地层运移的通道;延10、延9油藏主要受沉积相带的控制,河道砂体为油气富集的有利沉积相带,三角洲平原煤系沼泽为其良好的盖层。

Early-middle Jurassic sedimentary facies and its relationship with the hydrocarbon migration and accumulation in Baihe area of Ordos basin

In Baihe area of Ordos basin,Yan'an formation is characterized by gentle stratum,undeveloped structure,small reservoir distribution range and high yield.Aiming at the characteristics,the research on early-middle Jurassic sedimentary facies and its relationship with the hydrocarbon migration and accumulation has been carried out.By using lithology and logging curves,the types of sedimentary facies,the microfacies have been identified and divided.The results indicate Fuxian formation and Yan-10 member belong to braided river sedimentary bodies and developed sedimentary microfacies such as channel sand dam,diara,flood land and river flood swamp.Yan-9 member belongs to delta plain sedimentary system and developed sedimentary microfacies such as distributary channel and distributary bay.At the same time,based on the residual strata thickness distribution of Chang-1 and Chang-2,the ancient landform characteristics of the Jurassic have been restored.Studies have shown that thick sand layer of Fuxian formation was pressure relief opening of lower overpressure and acted as migration channel.Mainly controlled by sedimentary facies,channel sand bodies of Yan-10 and Yan-9 reservoir are of favorable sedimentary facies belt for oil and gas enrichment,with delta plain coal swamp acting as its good cap rock.