马朗凹陷条湖组凝灰岩致密储层特征及形成条件分析

Characteristics and formation conditions of tight tuff reservoir of Tiaohu Formation in Malang Depression

马朗凹陷条湖组凝灰岩致密油藏是近年来三塘湖盆地的重点勘探领域之一,明确其储层特征及形成条件对于深化三塘湖盆地凝灰岩致密油勘探具有重要意义。以岩心观察、薄片鉴定和全岩矿物分析为基础,结合场发射扫描电镜和毛管压力曲线等资料,开展储层微观特征研究,同时,采取井震结合方法,利用振幅、频率属性预测凝灰岩致密储层分布。结果表明:马朗凹陷条湖组凝灰岩致密储层主要由晶屑、玻屑组成,且富含有机质,脱玻化孔发育,具有中孔、特低渗、高含油饱和度的特征;缺少陆源碎屑物质供应的相对稳定的浅湖—半深湖环境是凝灰岩致密储层形成的关键;距离火山机构一定范围内的火山洼地控制着有效凝灰岩致密储层的平面展布;脱玻化及溶蚀作用对凝灰岩储集性能的改善至关重要。马朗凹陷北斜坡的火山洼地是凝灰岩致密储层发育的有利场所,L1西、L104H东及M7西南等区块是下一步开展致密油勘探的有利目标区。

The tight tuff reservoir of Tiaohu Formation in Malang Depression has become one of the key fieldsfor exploration in Santanghu Basin in recent years.The reservoir characteristics and formation conditions are ofgreat significance for deepening the exploration of tight tuff reservoir in Santanghu Basin.Based on the data ofcore observation,thin sections,whole rock X-ray diffraction,field-emission scanning electron microscope andmercury capillary pressure,the micro-characteristics of tight tuff reservoir were studied,and the distribution oftight tuff reservoir were characterized according to the data of amplitude,frequency by combining drilling andseismic method.The results show that the tight tuff reservoirs are mainly composed of crystal chips and glass chips,and rich in organic matter,with devitrified pores developed.The reservoir has the features of medium porosity,ultra-low permeability and high oil saturation.The stable shallow-semi deep lacustrine environment whichis lacking of terrigenous materials is the key for forming tight tuff reservoir,volcanic depression within a certainrange from the volcanic apparatus controls the distribution of effective tight tuff reservoir,and devitrification anddissolution are critical for improving the reservoir properties of tuff.The volcanic depressions in the northernslope area of Malang Depression are favorable for the development of tight tuff reservoir,the west blocks ofL1well and east blocks of L104well,south west blocks of M7well in Malang Depression are the next favorabletargets for tight oil exploration.