川中地区侏罗系致密砂岩储集层成因及“甜点”预测

Genesis and Sweet Spot Prediction of Jurassic Tight Sandstone Reservoir in Central Sichuan Basin

四川盆地侏罗系凉高山组和沙溪庙组一段储集层,为典型的特低孔、特低渗致密砂岩储集层,非均质性强,"甜点"发育区预测难度大。为预测储集层"甜点"有利区,利用岩心、薄片、扫描电镜、X射线衍射、包裹体分析等方法,开展了储集层特征及其形成机制研究。结果表明,四川盆地侏罗系致密砂岩储集层为相控砂体叠加中成岩期溶蚀作用而成,中后期构造裂缝提高了其储集能力。储集层"甜点"主要受沉积砂体、成岩溶蚀和构造裂缝控制,滩坝、分流河道和河口坝微相砂体溶蚀相与烃类充注相及裂缝发育的叠合区,为储集层"甜点"发育的有利区。凉高山组储集层"甜点"有利区分布于公山庙、龙岗—营山、莲池—充西等地区;沙一段储集层"甜点"有利区分布在公山庙、龙岗9井区、税家槽和大成—广安等地区。

The reservoirs of Jurassic Lianggaoshan formation and Sha-1 member of Shaximiao formation in Sichuan basin are typical extra?low porosity and extra-low permeability reservoirs with strong heterogeneity and great difficulties to predict sweet spots.To predict the favorable areas of sweet spot,the paper studies the reservoir characteristics and its forming mechanism based on the analysis of core,thin section,SEM,X-ray diffraction and inclusion.The study results show that the Jurassic tight sandstone reservoirs are the products of the dissolution of facies-controlled sandbodies during the middle diagenetic period in the Sichuan basin and the structural fractures formed in the middle and late periods can improve the reservoir capability.The sweet spots in the reservoirs are controlled by sedimentary sandbody,dia?genetic dissolution and structural fractures,and mainly distributed in the areas where microfacies such as beach bar,distributary channel and river mouth bar,hydrocarbon charging phases and fractures superimpose with each other.The sweet spots of Lianggaoshan formation are mainly found in the areas of Gongshanmiao,Longgang-Yingshan,Lianchi-Chongxi etc.;and the sweet spots of Sha-1 member are main?ly distributed in the areas of Gongshanmiao,Wellblock Longgang?9,Shuijiacao and Dacheng-Guang’an etc.