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Main fields in the Republic of Tatarstan have entered the closing stage of development characterized by high extent of reserves depletion (86 % of OOIP) and increase of the share of unconventionsl hard-to-recover reserves (from 33 % to 80 %). A considerable portion of PJSC TATNEFT’s unconventional reserves (36 %) is found, primarily, in carbonate and carbonate-silicious (shale) low porosity/permeability or fractured reservoirs, which are very challenging targets. In this light, study of low-permeability and porous reservoirs has recently acquired a prime importance. Comprehensive studies are needed to understand stress and strain properties of reservoir rocks in challenging geomechanical in-situ conditions. To understand fracturing pattern of carbonate reservoirs in Tatarstan, the Company has been employing different survey methods, including aerial and space imagery, side-view seismic location (SVSL), offset vertical seismic profiling, tracer surveys, core analysis, including oriented and quick capture cores, 3D CDP seismic survey. Particular attention has been given to analyses of drilling troubles and vertical and horizontal wells’ performance. The results obtained make it possible to select optimal orientations of horizontal wellbores with a view to maximize future production. This paper presents the Bavlinskoye oil field case study. Recommendations on downhole surveys are presented, as well as guidelines to select an optimal orientation of a horizontal wellbore in fractured reservoirs.