CO2-Responsive Nanogel Transportation and Plugging Efficiency in Sandstone Rock for Enhanced Gas Storage Efficiency

CO2 flooding can improve hydrocarbon recovery and store a substantial volume of CO2 in reservoirs. However, high-permeability zones in reservoirs can cause early CO2 breakthrough, which significantly reduces CO2 sweep efficiency and gas storage efficiency. In this circumstance, in-depth fluid diversion is required to improve gas storage. However, traditional gels are primarily effective in sealing near wellbore fractures or large flow channels but cannot penetrate and treat in-depth regions of the reservoir. To remediate in-depth heterogeneity, a CO2-responsive nanogel is developed. After initial swelling, this nanogel can further swell when exposed to CO2, enabling in-depth delivery and plugging. This study explores the transport behavior and plugging efficiency of CO2-responsive nanogel in sandstone formations for enhanced gas storage efficiency. The research aims to evaluate the nanogel's adsorption and desorption behavior, ability to divert CO2 flow, and plugging efficiency to CO2 and brine, thereby improving gas storage efficiency. CO2-responsive nanogel was prepared using 1% NaCl brine and aged at 65°C for 24 hours. Core flooding experiments were conducted using sandstone cores of varying permeabilities to investigate nanogel filtration, adsorption-desorption behavior, transport, and plugging efficiency. Adsorption-desorption experiments confirmed that nanogel adsorption follows the Freundlich isotherm, with 92.9% of the adsorbed nanogel being desorbed from the rock surface. The transportation test reveals that the desorbed nanogel can be transported to the in-depth area. Once delivered into the in-depth, the later injected CO2 can swell the nanogel and form an efficient plugging. The in-depth plugging is beneficial for gas diversion during CO2 injection. Plugging efficiency tests demonstrated a significant increase in the nanogel's plugging efficiency, with improved residual resistance factors (Frr) for CO2 and brine. The nanogel effectively reduced CO2 permeability and enhanced conformance control, mitigating early CO2 breakthrough, hence improving CO2 storage efficiency. This innovative nanogel demonstrates targeted plugging capability and strong potential for deep reservoir penetration. The novel properties of this nanogel make it an innovative solution for in-depth plugging and fluid diversion, which improves CO2 storage efficiency. The findings contribute new insights into nanogel-based conformance control, providing practical guidelines for optimizing CO2 storage efficiency and conformance control in CO2 flooding.