镇泾地区延长组碎屑岩古风化壳研究

STUDY ON THE WEATHERED CRUST OF CONGLOMERATE IN UPPER TRIASSIC YANCHAGN FORMATION OF ZHENJING FIELD

镇泾地区延长组碎屑岩古风化壳中见有良好的油气显示,是下一步油气勘探的重点。利用测井资料、铸体薄片、背散射、微量元素等资料,对研究区延长组碎屑岩古风化壳特征进行了研究。结果表明碎屑岩古风化壳主要包括水解带和淋滤带,水解带主要表现为一套厚度稳定的泥岩,可作为区域性盖层;而淋滤带由于大气淡水的淋滤作用,长石等易溶矿物发生蚀变,形成次生孔隙极为发育的砂岩储层,是致密砂岩中的"甜点",越靠近不整合面,储层物性越好。淋滤带"甜点"主要发育在前侏罗纪古地貌的斜坡上。这种结构具有良好的储盖组合,如果发育圈闭,可以形成具有一定规模的油气藏。

There is a favorable oil sign in clastic weathered crust of Zhenjing field,making it the next important exploring target.The clastic weathered crust of Yanchang Formation is researched by using well logging data,thin-sections of the cast,trace elements,BES and so on.It is showed that the weathered crust includes hydrolyze zone and leaching zone.Hydrolyze zone is made up of stable mudstones,and can be used as cap rocks.Because fresh water leaching,then feldspar and water-soluble minerals are altered,leaching zone is full of sandstones with a lot of secondary pores,which are 'desserts' of tight sandstones,and desserts can be found in slope of pale geomorphology of upper Jurassic usually.This structure has a good combination of reservoirs and caps.It can form large reservoirs if the traps are developed.