The article reviews a fast-track high-quality evaluation approach to the net pay reservoir thickness in a well-to-well space. The review is based on rocks the upper-Jurassic (J_1-1) Vasyugan suite exemplified by two areas in Western Siberia. The presence of certain geological prerequisites for reservoir formation supported by the use of historical data analysis made it possible to cluster the area in question interest according to the level of confidence in the availability of net pay thicknesses. The approach described in the article has been instrumental in optimizing the drilling program by mitigating cost risks. New wells delivered corroborating evidence of data reviewed.