苏北盆地溱潼凹陷古新统阜宁组二段侵入岩围岩变质带储层特征及其成藏意义

Reservoir characteristics and hydrocarbon accumulation significance of metamorphic zones of intrusive rocks and surrounding rocks in second member of Paleocene Funing Formation in Qintong Sag,Subei Basin

火山岩油气藏是油气勘探的重要领域之一。苏北盆地溱潼凹陷侵入岩分布广泛,油气显示活跃,已成为我国东部陆相盆地油气深化勘探和规模增储的重要领域,具备良好的勘探前景。然而,目前针对火山岩对泥页岩围岩储层及其成藏影响的研究较为缺乏,泥页岩围岩变质带能否作为勘探重点领域有待深入评价。为了推动苏北盆地侵入岩围岩变质带新类型油藏勘探,以溱潼凹陷阜二段侵入岩围岩变质带为研究对象,综合岩心、薄片、全岩、测井等资料,系统揭示了泥页岩变质带储层特征,明确了岩浆侵入对阜二段变质带油气成藏的贡献。研究表明,溱潼凹陷阜二段泥页岩受岩浆侵入影响,泥页岩围岩发生蚀变形成环状变质带储层,岩浆的侵入具有明显“增储作用”;变质带储层发育孔隙、裂缝两类储集空间,储层发育程度受侵入岩厚度及烘烤强度控制,岩浆的侵入具有“催熟作用”,同等深度下泥页岩Ro可增加0.4%~0.5%;阜宁组侵入岩形成于吴堡期—三垛期,火成岩侵入形成环状变质带的时间早于油气充注期,具有良好的成藏匹配关系。受岩浆侵入、侵入岩空间分布以及源储匹配关系控制,溱潼凹陷阜二段侵入岩围岩变质带具有源储一体、近源富集的特征,是规模增储的新阵地。

Volcanic reservoirs play a crucial role in oil and gas exploration.The intrusive rocks in the Qintong Sag of the Subei Basin are widely distributed within active oil and gas deposits,making them a significant area for further exploration and reserve expansion in East China’s continental basins.Despite the promising explora-tion prospects,there is a research gap regarding the impact of volcanics on shale surrounding rock reservoirs and their accumulation potential.It is essential to evaluate whether the shale metamorphic zones could serve as a key exploration target.This study focuses on the metamorphic zones of intrusive rocks and surrounding rocks in the Qintong Sag’s second member of the Funing Formation.By integrating core,thin section,whole rock,and well logging data,this work systematically reveals the reservoir characteristics of the mud shale metamorphic zones and defines the contribution of magma intrusion to hydrocarbon accumulation in the metamorphic zones.The results indicate that magma intrusion alters the mud shale of the Funing Formation,resulting in a circular meta-morphic zone reservoir with enhanced reservoir properties.This reservoir exhibits two types of spaces,pores and fractures,with development dependent on the thickness and intensity of intrusive rocks.Magma intrusion also leads to a“ripening effect”,increasing the Ro of mud shale by 0.4%-0.5%at the same depth.The intrusive rocks of the Funing Formation were formed during the Wubao to Sanduo periods.The intrusion of igneous rocks created a circular metamorphic zone prior to the hydrocarbon charging stage,indicating a favorable accumulation match.Influenced by magma intrusion,spatial distribution of intrusive rocks,and the source-reservoir relation-ship,the metamorphic zones of intrusive rocks and surrounding rocks in the second member of Funing Formation in the Qintong Sag exhibit characteristics of integrated source-reservoir and near-source enrichment.This presents a new opportunity for significant reservoir enhancement on a large scale.