Influence of microbial textures on pore characteristics of microbial dolomites: A case study of Lower Cambrian Xiaoerbulake Formation in Keping area, Tarim Basin

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.