Calculation Of Porosity And Fracture Parameters Based On Rock Micro Image

Due to the influence of uncontrollable factors such as environment and illumination in the collection process,the brightness of the original micro photos of the collected rocks makes it difficult to directly observe the rock pores and fracture structures.In the process of calculating the porosity and fracture parameters of rock micro images,the traditional method of calculating rock pore structures need to be adjusted manually,which is complicated and difficult to operate.With the development of computer,digital image processing technology has been widely used in every field.In this paper,the digital image processing technology is applied to the calculation of porosity and fracture parameters of micro rock images.Compared with the traditional calculation methods,the digital image processing calculation method has the advantages of simple operation and strong intuitiveness,which can greatly improve the efficiency of processing micro rock images and provide a new idea for calculating the porosity and fracture parameters of micro rock images in geology.In this paper,two image processing software MATLAB and Image J are used to calculate the porosity and crack parameters of micro rock images.On basis of digital image processing technology,combined with image enhancement,edge detection,mathematical morphology,image segmentation and other methods,to achieve the calculation of the porosity and fracture parameters of micro rock images in five groups of rock samples.The experiment is divided into two parts.In the first part,the software Image J is used to calculate the porosity and fracture parameters of rock micro photos.Firstly,the rock microscopic photos are preprocessed by Image J,and the pre-processing methods include image type conversion and grayscale processing.Then Laplace transform is used to segment the preprocessed images,and the number of pores and the calculation of porosity are automatically carried out by selecting the specified rock background circle.Then through the edge detection and local operation to extract the crack and automatic statistics of crack number and crack rate.In the second part,the software MATLAB is used to calculate the porosity and fracture parameters of rock micro photos.Firstly,the rock micro photos are preprocessed by MATLAB,and the pre-processing methods include histogram equalization,etc.Then the enhanced rock images are segmented by the OTSU to calculate the porosity and detect the maximum porosity.After the threshold segmentation,the images are processed by mathematical morphology,and the cracks and impurities are separated successfully by the difference of the ratio of the long and short axes in minimum tangent rectangle,achieving the purpose of successfully extracting cracks and automatically obtaining the width and length of cracks.In this experiment,software MATLAB and Image J are used to carry out linear regression analysis on the calculated results of porosity and fracture of five groups of rock samples.It is found that in the rock samples containing only pores,the number of pores,total pore area and average pore area are significantly correlated with porosity.The linear regression relationship R²is about 0.96,and the corresponding P value of total pore area is about 1.83×10^-13,which has the greatest influence on porosity.In the samples containing pores and fractures,the maximum pore diameter,fracture width and fracture length have a great correlation with the porosity of the rock.The linear regression relationship R²is about 0.88,and the P value corresponding to the fracture width is about0.1×10^-3,which has the greatest influence on the porosity.Finally,the results show that the images processed by Image J are more beautiful than the original rock image.The linear analysis of the porosity results of group 21 and group 35 of rock samples calculated by software MATLAB and Image J shows that the two calculation methods are consistent with the calculation results of group 21 of rock samples.The calculation results of 35groups of rock samples have a large error.Compared with the software Image J,the calculation results of MATLAB are more consistent with the conclusion of geological understanding.