Clay minerals and their parageneses make sensitive indicators of diverse processes involved in transformation of the Valanginian terrigenous rocks in the North Khalmerpayutinskaya field by hot solutions. The latter ones used to form hydrothermal-metasomatic reservoirs and to transport HC. The amounts of mixed-layer bodies and the proportions of swelling (smectite) and non-swelling (chlorite, micaceous) constituent packages make it possible to estimate the trap quality and the probability of HC presence.