Reservoirs and Seals of C0₂ Pools in Yangxing-Huagou-Pingnan Area,Jiyang Depression

Key words: 
• reservoir seal /
• CO_{2 pool} /
• Jiyang Depression

Abstract: Jiyang Depression is one of the sub basins in Bohaiwan basin. Carbon dioxide (CO₂ pools occur in Yangxing Huagou Pingnan area, the center of Jiyang Depression. Reservoirs of the CO₂ pools are the marine carbonate rocks in lower Palaeozoic Era, the lake carbonate rocks and delta sandstone in Eogene System, and the fluvial sandstone in Neogene System. The marine carbonate rock reservoirs are in the north of the area and the reservoir spaces are the structural and solution gaps. The lake carbonate rock reservoirs are in No.4 and 1 sections of Shahejie Formation in Pinfangwang area. The delta sandstone reservoirs, which total thickness are 100m～600m,porosity range from 11.5%～33% and permeability from 6.5×10 ^-3 m²～83×10^-3 m², are in Shahejie Formation in Gaoqing Pingnan, Lingfanjia and Yangxing area, respectively. The fluvial sandstone reservoirs are widely distributed in Yangxing Huagou Pingnan area. In generally, the sand and mud ratios, porosity and permeability of the fluvial sandstone reservoirs in the north are higher than that in the south of the area. Seals of CO₂ pools in Yangxing Huagou Pingnan area are mudstone and compact conglomerate and they all are effective seals. The mudstone seals are mainly distributed in No.3 and 1 sections of Shahejie Formation in Eogene System and upper Guantao Formation and Minghuazheng Formation in Neogene System. The compact conglomerate seals, which permeability are very low, occur in No.4 section on the sub mountain in Balibo of the north of Yangxing Huagou Pingnan area.Comparison of reservoir and seal between CO₂ pools and hydrogen gas pools, two kinds of pools are of similar reservoir. And CO₂ pools have poor qualitiy seal.