Diagenesis controls on high-quality reservoirs of the Yingcheng-Shahezi formations in the Lishu Fault Depression, Songliao Basin

Through lithologic observation, thin section identification and mineral composition statistics, the high-quality sandstone reservoirs in the Cretaceous Yingcheng-Shahezi formations in different areas of the Lishu Fault Depression were studied in detail. The results showed that the high-quality reservoirs were mainly developed in sandstones with coarser grain size, higher soluble component content and lower rock debris content. The main diagenesis processes of the target layer in this area include compaction, cementation filling, dissolution and structural fissures. In the process of diagenesis, compaction and cementation reduced the pores of the reservoir, while dissolution formed a large number of secondary pores. The structural fractures were the migration channels and reservoirs of the late oil and gas. It was proposed that the reservoirs in this area have five main pore combinations such as “original pore type”, “porous dissolved type”, “dissolved pore type”, “fractured type” and “cracked type”. The main controlling factors affecting the pore development of high-quality sandstone reservoirs are sandstone fabric, dissolution and later structural fractures. The sandstone has good structure, strong dissolution, tectonic fracture and large single layer thickness, and the interval and area adjacent to the source rock are the direction and target for future exploration.