川东北三叠系飞仙关组鲕滩气藏有利储集层的形成与分布

Formation and distribution of Triassic Feixianguan oolitic bank favorable reservoir in the NE Sichuan Basin

川东北地区三叠系飞仙关组鲕滩气藏是近年四川盆地碳酸盐岩天然气勘探取得重大突破的领域,目前在中国石油探区内已发现罗家寨、渡口河、铁山坡等大中型气藏。对鲕滩气藏白云岩储集层进行岩心观察、显微薄片分析,并进行微量元素、流体包裹体、X衍射、阴极发光及电子探针等分析,结果表明,白云岩化和多期溶蚀是形成优质白云岩储集层的关键因素,混合云化与埋藏云化的叠加作用是形成孔隙性白云岩储集层的基本条件。飞仙关组鲕滩气藏储集层经历了4期溶蚀作用,即同生期溶蚀作用、浅埋期溶蚀作用、深埋期溶蚀作用和抬升期溶蚀作用,形成优质白云岩储集层的主要溶蚀作用是浅埋期和深埋期的溶蚀作用。优质白云岩储集层主要分布在台缘鲕粒滩相带,纵向与亮晶鲕粒灰岩呈韵律性互层,横向主要分布在鲕粒滩坝靠近潟湖—潮坪一侧。

Some giant gas reservoirs have been found by PetroChina in Luojiazhai, Dukouhe, and Tieshanpo in the Sichuan Basin. The analyses of core, thin sections, minor element, liquid fluid inclusion, XRD, cathodoluminescence and electron microprobe suggest that dolomitization and dissolution are the key factors, and mixing dolomitization and buried dolomitization are the basic factors for forming favorable reservoirs in Feixianguan Formation. In the oolitic bank reservoirs four periods of dissolution can be identified including the surface meteoric water dissolution, organic water dissolution during shallow-buried, organic water dissolution during deep-buried period and the dissolution in the basin risen up, of them the organic water dissolution during the shallow-buried and deep-buried periods are the important dissolutions for forming favorable dolomite reservoirs. The favorable dolomite reservoirs are mainly distributed in the oolitic bank of shelf margin, vertically interbedding with sparry oolitic limestones and literally distributed on the lagoon-tidal flat side of the oolitic bank.