Changes in the Fracture and Intergranular Porosity in Rock Fracture Preparation

The method proposed by the authors makes it possible to determine the nature of changes in two components (intergranular and fracture) of the total porosity. Changes in the fracture and intergranular porosity were investigated during fracture nucleation of sandstone samples under modeling in situ conditions. Sandstone samples were held at constant confining and pore pressure modeling in situ conditions. At the same time, only a slight decrease in the total and intergranular porosity was observed. However, only in the sample with an initially large fracture porosity was an increase in fracture porosity observed. Growth of additional axial compression reduced all types of porosity. Fracture preparation of the sample with an initially small fracture porosity was predominantly accompanied by a decrease in total and intergranular porosity and increase in fracture porosity, i.e., growth of microcracks. At the same time, during fracture preparation of a sample with an initially large value fracture porosity, an increase in total and intergranular porosity and decrease in fracture porosity were observed, which is characteristic of dilatancy processes. Differences in the fracture nucleation of sandstone samples were revealed, which indicates that their initial fracture porosity has a significant effect on them.