Enhancing Subsurface CO₂ Storage Monitoring and Sensing: A Novel Long-Term, Real-Time Wireless Communication System

Long-term monitoring and sensing are extremely important to prevent leakage for subsurface CO2 sequestration. Traditional wired communication methods could lead to potential leakage pathways for CO2, while the underground wireless signal transmission faces challenges in extremely low channel capacity and energy efficiency for long distance. In this article, we focus on resolving these challenges by developing a highly efficient underground wireless communication system. This system is designed for sensing applications, enabling long-distance monitoring of subsurface CO2 storage. The system is built on a series of toroidal transceivers wrapped around a highly conductive casing string, enabling wireless signal transfer deep below the surface with high efficiency. By eliminating the need to perforate the casing or embed an umbilical in the cement annulus, this design keeps the well integrity and minimizes potential leakage risks. More importantly, the metal casing amplifies the efficiency of wireless signal transfer, providing a directed pathway for electric current, rather than allowing omnidirectional radiation losses in the subsurface. The design of the toroidal transceiver, together with its operational parameters—such as ferrite core sizes, coil wire diameter, number of coil turns, operating current and frequency, and transmitter placement—has been optimized for enhanced signal reception. Using the optimized design, for an 800-m-long subsurface wireless system, the channel capacity could improve about 14 000 times from 0.35 bps to 5 kbps, and the energy efficiency improves $10^{{9}}$ times from $10^{-{3}}$ to $10^{{6}}$ bit/J. In the end, we built a scaled-down wireless communication system with universal software radio peripheral (USRP) as transceivers, test it at different symbol rates, and compared the bandwidth from voltage signal curve and constellation figures.