龙凤山地区营城组深层优质储层形成机理

摘要

近年来,在长岭断陷龙凤山地区埋藏深度大于3000m的营城组地层中,已有多口钻井获得工业油气流,显示出良好的油气勘探潜力,但其优质储层的形成机理与控制因素均不明确,制约了进一步的油气勘探和开发.综合利用岩心观察、铸体薄片分析、CT扫描、物性测试及恒速压汞等方法,对龙凤山地区优质储层的形成机理与控制因素进行了分析.结果表明:营城组储层物性主要受成岩作用的控制,根据胶结物的特征可划分出压实致密砂岩、绿泥石胶结砂岩和浊沸石胶结砂岩3种类型砂岩;在淡水充注和湖水作用的控制下,储层胶结作用和溶蚀作用均具有明显的分带性,并据此建立了不同砂岩的发育模式.中成岩期浊沸石胶结砂岩受到有机酸的溶蚀,在扇三角洲外前缘形成优质储层分布区,有利于油气的聚集成藏,可作为下一步勘探开发的“甜点”区域.%With the new exploration development of Longfengshan area in Changling graben,it is proved that the Yingcheng Formation with burial deeper than 3000 m has favorable gas exploration potential.Although com-mercial oil and gas flow was produced in several wells,the formation mechanism and controlling factors for high-quality reservoirs remained undefined.Based on the data of core observation,casting thin sections,computed tomography (CT) scanning,physical properties testing and constant-rate mercury penetration,the formation mechanism and controlling factors for high-quality reservoirs were analyzed.The results show that the reservoir property in the study area is mainly controlled by diagenesis.According to this,the reservoirs were divided into compacted tight sandstone,chlorite-cemented sandstone and laumontite-cemented sandstone.The distribution of cementation and dissolution shows the characteristics of obvious zonation under the control of fresh water filling and lake water.The distribution model of various types of sandstones was established.During the middle diage-netic stage,the laumontite was dissolved by organic acids produced by source rock,and formed high-quality reservoirs in outer skirt of the fan delta front,which is the “sweet point” for the further hydrocarbon exploration.