CO_(2) solubility and mineral trapping behavior in high-salinity reservoirsOA

CO_(2) solubility and mineral trapping behavior are critical to the stability and effectiveness of integrating CO_(2) geological storage synergistically with gas field produced water(GPW)reinjection,a promising strategy for achieving co-benefits in pollution mitigation and carbon emission reduction.To investigate CO_(2) solubility-mineral trapping during co-injection with GPW-characterized by high salinity and complex ion composition-a series of CO_(2)-GPW-rock interaction experiments and geochemical simulations were conducted using sandstone and limestone samples,together with simulated GPW of salinities ranging from 47.6 to 225.5 g/L.The results indicate that:(1)CO_(2) solubilitymineral trapping behavior is governed primarily by CO_(2) pressure,injection method,and GPW salinity,and is further influenced by calcium concentration and rock mineralogy.Under the experimental conditions,the CO_(2) solubility-mineral trapping capacity ranged from 9.03 to 11.01 g/L,with corresponding trapping proportions between 74.56% and 87.38%;(2)within a closed CO_(2)-GPW-rock reactive system,the timedependent CO_(2) solubility-mineral trapping proportion can be described by the cumulative Weibull model.The CO_(2) solubility-mineral trapping capacity increases with increasing CO_(2) pressure but decreases with increasing GPW salinity.A slight elevation in calcium concentration enhances CO_(2) solubility-mineral trapping at low CO_(2) pressures,despite concurrent increases in ionic strength and brine salinity.When the GPW salinity remains constant,the variation in calcium concentration exerts only a limited influence on CO_(2) solubility-mineral trapping;(3)a higher reactive mineral content in the reservoir enhances CO_(2) solubility-mineral trapping,and intermittent injection significantly improves this process;(4)the cumulative solubility-mineral trapping capacity can reach 22.13-38.01 g/L,representing 2.28-3.04 times the capacity achieved under single-injection conditions.These findings underscore the importance of carefully selecting storage sites and designing injection schemes in CO_(2) geological storage operations.