Abstract <p>This study examines post-sedimentation changes in sandstone reservoirs in the Cretaceous deposits in the western part of the Gydan Peninsula. Structural-mineral associations formed under conditions of background subsidence catagenesis and superimposed fluid catagenesis have been studied using the method of stage analysis. The focus is on the mechanisms of material redistribution, which lead to changes in the reservoir properties of the rocks. The key processes contributing to secondary porosity formation include leaching and decompaction, driven by fluid activity. The resulting data can be used to predict the hydrocarbon potential of reservoirs and identify optimal zones for development.</p>