The strength properties of the rock determine many physical processes occurring in the formation and at the bottom of the well. Deformation and destruction of rocks under the influence of external forces can be both a positive and a negative factor for working with formations at all stages of development. To create the optimal design of the well drilling trajectory, select the optimal development project, the fluids extraction rate from the formations, efficient planning and implementation of hydraulic fracturing procedures, prevention of emergencies during drilling and operation and reduction of oil recovery due to irreversible loss of reservoir properties and solving many other problems, it is necessary to consider possible destruction of the rock. The Mohr-Coulomb envelope (rock strength passport) can be used as a strength criterion for such tasks, it characterizes the boundary values of stresses in the rock, at which its destruction occurs according to the Mohr-Coulomb theory.
At article discusses three methods for determinate strength passports based on the results of laboratory studies of rock samples: multistage loading of the sample, assessment of the sample fracture after triaxial compression strength test, the use of "twin" samples for testing. The features of each method, its advantages and limitations are disclosed, examples of construction of strength passports for rocks from fields in Western Siberia are shown. According to the research results, the most preferable is the use of "twin" samples. However, this method is associated with technical difficulties.