潜江凹陷潜江组盐间页岩油储层发育特征及影响因素

Characteristics and influencing factors of inter-salt shale oil reservoirs in Qianjiang Formation,Qianjiang Sag

以江汉盆地潜江凹陷潜江组潜3~4油组盐间页岩油储层为研究对象,通过岩心观察、岩石薄片鉴定、氩离子抛光-扫描电镜、低温氮气吸附及高压压汞等技术手段对泥页岩的岩相特征、储集空间类型、储层物性特征及影响因素进行研究。结果表明:潜江组潜3~4油组盐间页岩油储层矿物组成复杂,主要发育层状云(泥)质钙芒硝岩相、纹层状泥质云岩相、纹层状云质泥岩相、纹层状泥质灰岩相、纹层状灰质泥岩相和块状云岩相等6种岩相类型;储集空间包括层间缝、晶间孔、晶间溶孔及黏土矿物晶间孔;储层孔隙度平均为11.4%～18.9%,渗透率平均为2.635～4.827mD,属于中孔、特低渗透储层;纹层状泥质云岩相和块状云岩相的物性和含油性好,为最有利的岩相;压实作用及后期硫酸盐矿物的充填作用是造成储层物性变差的主要原因。

The samples of shale oil reservoirs from the Qian34 formation of Qianjiang Sag in Jianghan Basin were collected for a series of experimental studies including core description,thin section analysis,Argon Ionization-Field Emission Scanning Electron Microscopy(AIP-FESEM)analysis,low-temperature nitrogen adsorption,high-pressure mercury injection,etc.to analyze the characteristics of lithologic facies,reservoir storage space types,reservoir physical properties and their influencing factors.The results indicate that the inter-salt shale oil reservoirs in Qian34 are characterized by complex mineral composition.There are six types of lithofacies in the study area,which includes layered dolomite(argillaceous)calcium mangerite lithofacies,laminated argillaceous dolomite lithofacies,laminated dolomite mudstone lithofacies,laminated argillaceous limestone lithofacies,laminated lime mudstone lithofacies and massive dolomite lithofacies.The main reservoir storage space of inter-salt shale oil are interlayer fractures,intercrystalline pores,intercrystalline dissolved pores and clay intracrystalline pores.The average porosity is 11.4%-18.9%and the average permeability is 2.635-4.827 mD.The formation belongs to mid-porosity and extra-low permeable formation.Laminated argillaceous dolomite lithofacies and massive dolomite lithofacies are the most favorable facies types with good physical properties and high oil-bearing characteristics.Compaction and authigenic sulfate minerals filling are the main reasons for the poor physical properties of the reservoir.