多孔类岩石孔隙率测量方法适用性评价——以珊瑚礁灰岩为例

Evaluating the Applicability of Porosity Measurement Methods for Porous Rock—Taking Coral Reef Limestone as an Example

摘要: 孔隙率是反映岩石孔隙结构发育情况的重要指标。然而对于一些孔隙结构极度发育的多孔类岩石，不同的孔隙率测量方法有着不一样的适用性。本文以中国海南省一种生物成因沉积岩——珊瑚礁灰岩为例，讨论了饱水法、水银压汞法和基于CT扫描图片的图像法这三种孔隙率测量方法对该种岩石的适用性。测量结果表明：水银压汞法和经过自适应阈值分割的图像法所测得的孔隙率数值相近，约为0.48；而饱水法的测量结果显著偏小，为0.35；而基于两种全局阈值分割方法的图像法的测量结果则偏大，约为0.55。对珊瑚礁灰岩的孔隙连通性进行分析发现珊瑚礁灰岩的孔隙连通性极好，故认为高压水银压汞法所测量得珊瑚礁灰岩孔隙率数据最为准确，同时也说明经过局部阈值分割法处理的二值化图像更适宜于珊瑚礁灰岩这类孔隙结构极度发育多孔类岩石的孔隙率计算。

Abstract: The porosity is an important index to reflect the development of pore structure of porous rock. However, for some porous rocks with extremely developed pore structure, different porosity measurement methods have different applicability. In this paper, we discuss the applicability of three porosity measurement methods, water-saturated method, mercury intrusion porosimetry (MIP) method and image method based on CT scanning technique, to porous rock, using a biogenic sedimentary rock, i.e., coral reef limestone, collected in Hainan Province, China, as an example. The results show that the porosity measured by the MIP method and the image method with adaptive threshold segmentation are similar, which is around 0.48; the porosity measured by the water-saturated method is significantly smaller, which is 0.35; and the porosity measured by the image method using two global threshold segmentation approaches are larger, which are approximately 0.55. The analysis of pore connectivity of the coral reef limestone sample reveals that the pore connectivity of the sample is high. Therefore, the porosity measured by the high-pressure MIP method is considered to be the most accurate, which also indicates that the binarized images processed by the local threshold segmentation method are more suitable for the porosity calculation of coral reef limestone with a hyper-developed pore structure.