Fine characterization of pore structures in coral reef limestones based on three-dimensional geometrical reconstruction

A digital core technique was utilized for three-dimensional (3D) reconstruction of reef limestone and the maximum-ball algorithm was adopted to extract the pore network model, thus realizing the quantification and 3D visualization of pore throats in reef limestone. Meanwhile, the digital core technology was combined with the fractal theory to calculate the two-dimensional (2D) and 3D fractal dimensions of reef limestone of four different densities. The results show that the slice-by-slice porosity of reef limestone is highly discrete, and the porosity of reef limestone gradually reduces as its density increases. The pore and throat radii of reef limestone of different densities both follow the logarithmic normal distribution while the throat length follows the Gaussian distribution. The coordination number of reef limestone is mainly distributed in the range of 2.73 to 8.65. As the density increases, pore connectivity gradually weakens. The sphericity of reef limestone exhibits a strong exponential correlation with the pore radius The fractal dimension of reef limestone is mainly distributed in the range of 2.392 to 2.697 and tends to decline gradually with the increase in density.