Quantitative study on reservoir diagenesis in Northern Dagang Structural Belt, Huanghua Depression

The sandstone reservoir experienced diagenesis of compaction, cementation, dissolution, and replacement in the Northern Dagang Structural Belt. The compaction intensity is quantitatively classified into six grades according to the relative content of grains, with different types of grain-contact. Compaction of the sandstone reservoir in the study area is from moderate (grade III) to moderate-intensive (grade IV). Cementation includes quartz overgrowth, calcite cementing, and clay mineral cementing. The quartz overgrowth occurs from 2 200 m to 3 300 m. Calcite cement is calcsparite. The precipitation depth of calcite cement is determined to be 2 300–3 100 meters using cathodoluminescence, inclusion thermometry, and so on. The authigenic clay mineral fills in the pores. Its distribution is related to burial depth. Dissolution includes corrosion of detrital feldspar and calcite cement. Compaction is related to burial depth, sandstone composition, and cementation. Cement precipitation is related to transformation of clay minerals and dissolution results from the thermal evolution of organic matter.