Selection of optimal strength criteria for the terrigenous Pashiyan horizon of the Romashkinskoe field Tashliyarskaya area

Abstract

In the process of oil reserves’ development, the in-situ stresses change. Knowledge of rock failure constraints will allow prediction of behavior of rock when subject to subsurface stress change. In this study, we used the results of studies of the Pashiyan sandstone core samples recovered from the Tashliyarskaya area well No. 14403. Six sets of samples, each consisting of three samples taken from the homogeneous intervals at the same depth, were used to determine the ultimate tensile strength, uniaxial and triaxial compressive strength in the in-situ conditions. An analysis of the methods for constructing a rock strength certificate, and comparison of the strength criteria described in State Standard 21153.8-88, the Mohr-Coulomb linear strength criterion and the non-linear Hoek-Brown criterion are provided. The Hoek-Brown criterion has the advantage of describing a non-linear increase in strength with an increase in overburden pressure and more adequately reflects the properties of rock. For the first time, a comparison of applicability of strength criteria obtained by different methods and based on the laboratory core analysis was made to determine their practical applicability. Comprehensive studies of the strength characteristics have never been previously conducted, and the results obtained will serve as the basis for further analysis and application in order to improve the development of the terrigenous Devonian Romashkinskoe field.