基于地质成因的砂岩储层微观孔隙结构分形特征分析

Analysis of Sandstone Reservoir Micro-pore Structure Fractal Based on Geological Origin

为查明储层微观特征与地质成因之间的联系,利用压汞、扫描电镜、铸体薄片、孔渗分析等资料,研究了松辽盆地大庆长垣不同渗透性砂岩储层的微观分形特征,并结合储层岩石学、成岩作用、次生孔隙的发育情况等分析了地质成因.研究表明:微观孔隙分形维数随储层渗透率降低而增大,反映孔隙复杂程度增加;中高渗储层孔隙分布在分形特征方面表现为二段式,大小孔喉分维数差异较大;低渗储层分形特征表现为一段式.从沉积过程看,储层物性越好,形成的大孔和小孔复杂程度差异越大,且大孔复杂程度高于小孔.从成岩过程看,大孔喉以溶蚀作用为主,小孔喉的胶结作用、压实作用均较强.高渗储层受沉积作用影响大,分形维数较小;低渗储层受成岩作用影响大,分形维数较大.该研究从成因上解释了不同渗透性储层微观特征的差异,对利用分形特征恢复地质信息具有一定指导意义.

To confirm the relation between micro-character and geological origin of sandstone reservoir,micro-pore fractal characteristics of different permeability sandstone reservoirs in Daqing Changyuan in Songliao Basin are researched with the data from mercury,scanning electron microscopy,cast sheet,porosity and permeability,and geological origin is analyzed with the petrology and mineralogy,diagenesis,and secondary porosity.The results show that the micro-pore fractal dimension increases with the lowering of reservoir permeability,which reflects the increased complexity of the pore.Two-stage of the fractal characteristics of pore distribution in middle and high permeability reservoir is shown.The fractal dimensions of large and small pore are quite different.The character of low permeability reservoir showes one-stage.View from the deposition process,the better reservoir properties is,the bigger the complexity difference of the large pore and small pore are,and fractal dimension of large pores are greater than that of small pores.From the diagenetic process,the macropore throat is mainly dissolved,and the cementation and compaction of the small pore throat are stronger.The high permeability reservoir is influenced by sedimentation and the fractal dimension is small.The low permeability reservoir is influenced by diagenesis and the fractal dimension is large.This study explains the difference of microscopic characteristics of different permeability reservoirs from the origin,and has certain guiding significance for the recovery of geological information by using fractal characteristics.