青西凹陷下白垩统含白云质泥岩与泥质白云岩储集层微观孔喉特征及控制因素

Microscopic Pore-throat Characteristics and Controlling Factors of the Lower Cretaceous Dolomite-bearing Mudstone and Argillaceous Dolomite Reservoirs,Qingxi Depression

岩石类型中的孔喉特征对储集层的研究具有重要意义。对青西凹陷下白垩统储集层中的含白云质泥岩和泥质白云岩进行薄片观察、矿物X衍射定量分析、场发射扫描电镜观察、Qemscan系统分析和压汞分析,结果发现,含白云质泥岩中黏土矿物含量高,发育黏土矿物层间孔,含部分黄铁矿晶间孔及微裂缝,粒内孔数量较少,微米级孔隙（孔径10-200μm）数量居多;泥质白云岩中白云石含量高,以矿物颗粒粒缘缝、粒间孔、微裂缝及有机质收缩缝为主,偶见有机质溶蚀孔、黄铁矿晶间孔,纳米级孔隙较多,主要为20-200μm。通过两类岩性中孔喉特征差异初步分析,认为矿物组成、压实作用、有机质成熟度是其主要影响因素。

Study on pore-throat characteristics is one important part of reservoir assessment. Studying pore-throat features in different lithologies has great significance in reservoir study. On basis of thin-section observation and X-ray diffraction analysis,field-emission electron microscope observation,Qemscan system and mercury injection analysis,dolomitebearing mudstone and argillaceous dolomite of the lower Cretaceous reservoir in the Qingxi depression were analyzed. The results indicated that the dolomite-bearing mudstone consists high contents of clay minerals,develops clay-mineral interlayered pores and contains some pyrite intercrystalline pores and microfractures with few intraparticle pores,in which micrometer-scale pores（diameter： 10-200 μm） are dominant. The Argillaceous dolomite mainly develops grain-edge fractures,interparticle pores,microfractures and organic matter contracted fractures,occasionally contains organic matter dissolved pores and pyrite intercrystalline pores,many of which are nanometer-scale pores,with diameters of 20-200 nm.Preliminary study had been conducted on the differences of pore-throat characteristics of the two lithologies and the results indicated the main controlling factors are mineral composition,compaction and the maturity of organic matter