普光气田三叠系飞仙关组储层为典型的相控型储层，由白云化程度很高的鲕粒滩体所构成，岩性主要为残余鲕粒、内碎屑以及泥粉晶白云岩等，储集空间类型多样，主要为粒内孔与晶间孔，局部发育少量裂缝。不同储集空间类型储层成因与岩相以及所在滩体部位、白云化作用等关系密切，其中，滩体底部发育海侵泥晶灰(白云)岩，常含鲕粒、砂屑等颗粒，鲕粒、砂屑呈泥晶结构，滩体低部位发育粒内孔鲕粒白云岩，鲕粒由微晶白云石构成，白云化程度低，而滩体中高部发育晶间孔残余鲕粒白云岩，鲕粒呈中粗晶残余结构；滩体顶部为泥粉晶白云岩，含有硬石膏晶体，储层物性极差，但易形成裂缝。这种鲕粒滩体岩性变化反映了随着水体变浅，组成鲕粒的白云石晶粒不断增大，白云化程度不断增强的特征。此外，碳氧同位素分析显示鲕粒细晶白云石δ¹⁸O值为负值，平均为-5.037‰(PDB)，δ¹³C值平均为1.596‰(PDB);微量元素分析中Sr含量和Na含量很低，SrO含量和Na₂O含量平均分别为0.018 72%和0.013 12%,FeO含量也低，平均为0.057 64%;X-射线衍射分析白云石的有序度低，平均为0.62，小于0.9;Mg/Ca值中碳酸钙摩尔分数高，平均为51.14%，大于50%;并且岩石薄片中基本未发现流体包裹体，少数发现少量单相流体包裹体，这些均表明组成普光气田鲕粒滩体中的白云石是在受大气淡水影响、氧化、低温、近地表条件下形成，综合显示为混合水白云化成因。

The Triassic Feixianguan Formation reservoir in the Puguang Gasfield is a typical phase-control reservoir and is composed of highly dolomitized oolitic shoal.It is dominated by residual oolitic dolomite,intraclast and micritic dolomites.The reservoir spaces are various and the dominant types are intergranular pores and internal pores (include intracrystalline pores).Few fractures are developed in local areas.Different types of reservoir space have very different physical properties,pore structure parameters and sensitivity characteristics.According to further analysis,it is proposed that the causes of different types of reservoir spaces are related to lithofacies and dolomitization.At the bottom of the beach,it developed transgressive micrite limestone (dolomites),including particles like oolitics and sand cuttings which are micrite structure.At the low location of the beach,it developed inner hole oolitic dolomite.The oolitics are usually composed of microcrystalline dolomite,which has low dolomitization.At the middle and high location of the beach,it developed residual coarse-grained intracrystalline pore residual oolitic dolomite and the oolitic is coarse-grained structure.At the top of the beach it mainly developed crystal dolomite,including anhydrite.The physical properties of reservoir gradually become poor,and it is easy to form fractures.The lithologic changes of the oolitic beach body reflect that as the water becomes shallow,grains of the dolomites increase constantly,and the degree of the dolomization strengthens constantly.In addition,the oxygen and carbon isotopic values demonstrate that δ¹⁸Ο of oolitic grain-refining dolomite is negative with an average of -5.037‰(PDB).The average of δ¹²C is 1.596‰ (PDB).The analysis of trace element show that Sr and Na are at a low level.The average content of SrO and Na2O is 0.018 72% and 0.013 12%,respectively.The average content of FeO is 0.057 64%.The x-ray diffraction analysis of dolomite order degree is low,i.e.,0.62 on average and below 0.9 generally.The CaCO₃ molar fraction in Mg/Ca is high,with an average of 51.14% and generally more than 50%.There′s nearly no fluid inclusion in the rock section,and some has little single-phase fluids inclusion.This shows that the dolomite of the oolitic beach body of Puguang was formed under the condition of the meteoric fresh water,oxidation,low temperature,and near the surface,which implies the dorag dolomitization causes.