Abstract:

     The Daqing Oilfield, situated in Songliao Basin of Eastern China, is a famous oilfield for its largest production of crude
oil in China. The Xujiaweizi fault depression, located in the north of the basin, covering an area of 4300 km2, developes large
amount of basaltic hydrocarbon reservoirs. In this paper, we analyze the geological features and reservoir characteristics of basaltic hydrocarbon reservoir in the depression. Combined with mineral and chemical compositions of basalts from ten deep drilling wells of the Xujiaweizi fault depression, we evaluate the feasibility of CO2 sequestration in hydrocarbon reservoir of basaltic rocks, and then estimate the CO2 storage capacity from mineral trappimg and gas reservoir trapping in basaltic rocks in the depression. Our results show that reservoir spaces are favorable sites for CO2 sequestration and minerals of the reservoir rocks are easily suffered tocarbonation. Meanwhile, the cap rocks of the hydrocarbon reservoirs can prevent the emission of CO2, and the stability of hydrocarbon reservoir can guarantee the safety of injected CO2. Therefore, hydrocarbon reservoir of basaltic rocks should be an idea target for CO2 sequestration. Estimates of theoretical capacity for CO2 storage assume that all the pore space freed up by the production of recoverable hydrocarbon reserves would be replaced by CO2. In this study, the capacity of CO2 mineral sequestration has been calculated for the mafic minerals in basaltic rock of the hydrocarbon reservoir based on the principle of water-CO2-rock reaction. Moveover, the theoretical storage capacity of the gas reservoir trapping has been estimated based on gas resources in reserved basals
from the local gasfield. According to our preliminary calculations, the potential capacity of mineral trappins for reaction with CO2 is about 89.33×108 tons, while capacity of gas reservoir trapping to CO2 storage is about 6.2×108 tons. So the total trapping capacity of CO2 sequestration for hydrocarbon reservoir of basaltic rocks from the Xujiaweizi fault depression is about 95.53×108 tons.

Key words: CCS (CO2 Capture and Storage), geological sequestration, basalt, potential capacity of CO2 sequestration, Xujiaweizi
fault depression