Reservoir characteristics and pore evolution in Sishilicheng area of Yanqi basin

By taking Sishilicheng area of Yanqi basin as an example, based on the study of reservoir petrology, diagenesis, physical properties and pore structure, combined with the structural-sedimentary-thermal evolution model of the basin, a prediction model of sandstone porosity evolution is established. The results show that the original porosity of the reservoir in Sishilicheng area is 35.00%, the porosity loss caused by compaction is 24.50%, and the porosity loss caused by cementation is 2.80%. At the end of early diagenetic period, for the reservoir with good connectivity of pore system, the final preserved porosity is about 12.50% due to the formation of secondary pores and oil-gas filling. For the reservoir with poor connectivity of pore system, the final porosity is only 7.70% due to no secondary pores and no oil-gas filling. The statistical relationship between high-quality reservoirs and sedimentary facies shows that most of the high-quality reservoirs are distributed in braided river delta plain branch channel and front underwater distributary channel sand body.