川北米仓山地区震旦系灯影组差异化岩溶作用分析

四川盆地灯影组以一套碳酸盐岩沉积为主，优质储层发育普遍受岩溶作用影响。川北米仓山地区早古生代为一个范围相对稳定且露出水面的陆地，在桐湾期与川中古隆起具有很好的可对比性。通过重点剖面碳、氧同位素特征分析及镜下观察，对灯影组二段和灯影组四段(下文简称“灯二段”和“灯四段”)不整合岩溶特征进行了系统对比。灯二段储层表现为葡萄状白云岩发育顺层、穿层溶蚀洞缝；而灯四段则以砂糖状白云岩晶间孔、藻纹层白云岩针状溶孔和角砾间孔隙为主，与前者相比灯四段表现为更多类型且更为发育的储集空间。灯二段、灯四段不整合面附近碳、氧同位素值由底及顶有逐渐变低的趋势，且灯四段白云岩碳、氧同位素值比灯二段整体较低，在纵向分布上更为偏负。综合说明了桐湾二幕较桐湾一幕构造抬升更为强烈，灯四段较灯二段受表生岩溶剥蚀影响更深，反映了桐湾运动不整合对灯影组储层发育起着主要控制作用。

Differential Karstification Analysis of the Sinian Dengying Formation in Northern Sichuan

The Dengying Formation in the Sichuan Basin is mainly a set of carbonate sediments,in which the high quality reservoir development is generally controlled by karst effects.In the Early Paleozoic,Micangshan area of northern Sichuan was an exposed land which was relatively stable,and it had good correlation with paleo-uplift of central Sichuan in the Tongwan Period.In this paper,through the analysis of carbon and oxygen isotopic characteristics in the key sections and microscopic observation,we systematically compared the unconformity karst features between the2^nd and 4^th members of Dengying Formation.The 2^nd member reservoir is characterized by grape-like dolomite which develops bedding,interspersed corrosion caves and fractures,while the 4^thmember develops sugar-like dolomite intercrystal pores,algae laminae dolomite acicular dissolved pores and breccia pores.Compared with the former,the 4^th member of Dengying Formation has more reservoir space types and they are more developed.Furthermore,carbon and oxygen isotopes near the unconformity of the two layers have a tendency to get lighter from bottom to top,and carbon and oxygen isotope value of the 4^th member of Dengying Formation is overall lower than that in the second member,as well as more negative in the vertical distribution.Based on the characteristics above,we can summary that compared to the first period of Tongwan Movements,the second period of tectonic uplift is more strong,leading to deeper supergene karst erosion effect in the 4^th member of Dengying Formation.As a result,it reflects that the unconformity of Tongwan Movements plays an important role in controlling the development of Dengying Formation reservoir.