微生物结构对微生物白云岩孔隙特征的影响——以塔里木盆地柯坪地区肖尔布拉克组为例

摘要

微生物结构是微生物白云岩区别于常规碳酸盐岩的重要特征,研究微生物结构与孔隙特征的关系是研究微生物白云岩储层成因和分布的关键.以塔里木盆地西北缘柯坪地区典型野外剖面肖尔布拉克组为例,选取凝块石白云岩、泡沫绵层石白云岩、叠层石白云岩及泥粉晶白云岩样品,通过实验测试表征其物性特征和孔隙结构特征,并与相应的微生物结构相关联,以分析微生物结构对孔隙特征的影响.根据成岩改造强度和性质的不同将样品分为3组,对比其孔隙特征来分析成岩作用的改造.结果显示,微生物结构与孔隙特征关系密切,沉积作用通过控制微生物结构来控制微生物白云岩的孔隙特征,而成岩作用则主要在沉积作用的基础上进行叠加改造,并受微生物结构的制约.%Microbial texture is an important characteristic of microbial dolomites compared to conventional carbonate rocks.Thus,studying microbial texture is the key to understand the origin and distribution of microbial dolomites.We selected thrombolite dolomite,foam spongy dolomite and stromatolite dolomite samples of the Xiaoerbulake Formation in Keping area in the northwestern Tarim Basin to test their petrophysical properties and pore structures. The test results were correlated with corresponding microbial textures to analyze their influence on pore characteristics. These samples were divided into three groups with different intensities of diagenesis alteration in order to analyze its effects. The results showed that the pore structures of microbial dolomites were closely related to their microbial textures. Sedimentation served as the dominating factor of pore structures with its controls on microbial textures, while diagenesis,under the restriction of microbial textures,changed the pore system mainly on the basis of sedimentation.