Features of Stress State Reconstruction in Carbonate Rocks on the Example of an Oil Field of the Republic of Tatarstan

The paper presents the results of laboratory studies of the physical and mechanical properties of carbonate rock cores from one of the oil fields in the Republic of Tatarstan. The experimental data obtained, together with the results of geophysical studies of wells and fracture data, were used to calculate the stress-strain state of the rocks. Horizontal stresses were calculated using the Eaton poroelastic model. The deformation coefficients at the depth of hydraulic fracturing were preliminarily determined. The minimum horizontal stress was determined as the fracture closure pressure, and the maximum horizontal stress was calculated from the stress diagram (combining the rock failure criterion and the classification of tectonic states). The elastic moduli obtained from laboratory studies were used in the stress reconstruction. As a result, the values of the stress along the borehole section were calculated and the tectonic regime was determined. The dependence equations for the strength properties of the rocks composing the section were obtained and the strength values along the entire borehole were calculated. The geomechanical model was used to calculate the dependence of fracture pressure on fracture length and to assess the conditions of uncontrolled fracture growth.