CO2 BEHAVIOR IN OPEN AQUIFERS, INSIGHTS FROM VERTICAL HETEROGENEITY AND STRUCTURE CONFIGURATION

Abstract

This study investigates the behavior of the CO2 plume in open aquifers by the change in important properties. Vertical permeability, with the creation of 8 different varying permeability properties with depth keeping the same average vertical permeability (PERMZ, PERMZD, PERMLHL, PERMHLH, RandPermZ, RandPermZD, RandPermLHL, and RandPermHLH). The dip of the structure was done using nine different dip angle models ranging from 0° to 30°. In addition, it assesses the effects on injection rate under the permeability and dip variations using three different injection schemes (constant rate, stepwise increasing rate, and stepwise decreasing rate) under a constant total volume injected in all the cases. This is achieved after creating a smaller-scale model of an open aquifer populated with petrophysical and fluid conditions representative of the Smeaheia dataset. Results show that during the injection time, each extra degree on the dip will increase the velocity by 28% on average. The plume's migration path will be significantly affected by the gravitational segregation of CO2, particularly in formations with dip angles higher than 3°. Additionally, heterogeneities within the aquifer, such as layers with differing permeability, result in preferential pathways. The sweep area is positively impacted by lower dip angles. The injected CO2 is less likely to bypass large sections of the reservoir, allowing for more efficient utilization of the available pore space. This increased contact with the rock matrix not only improves the storage capacity but also enhances the potential for capillary trapping. The detailed map of how permeability varies throughout the entire reservoir is key to predicting the movement and behavior of a CO2 plume over time. This is assessed under the same average permeability for all the reservoirs. The injection rate pattern affects the evolution of the pressure in the reservoir. The High to low rate (HL), shows a steeper trend of the pressure, reaching the highest values in less time. In addition, in all the sensitivities the initial injection affects the pressure behavior during the injection time and afterwards, at high initial rates the final pressure at the end of injection and after injection will be higher than the constant rate, (C), and Low to high rate, (LH).