Electrically responsive wellbore cement for integrity monitoring: coupled electromechanical behavior of graphene-modified cement systems

Wellbore cement provides zonal isolation and structural integrity in subsurface energy systems but offers limited capability for continuous integrity monitoring. This study evaluates the self-sensing potential of field-representative API Class H wellbore cement containing 0.3, 0.5, and 1.0 wt% graphene nanoplatelets (GNPs), prepared using practical slurry formulations and industry-standard mixing procedures. Electrical resistance was characterized over 1 Hz–10 kHz, followed by coupled unconfined compressive strength (UCS)–electrical resistance monitoring under saturated conditions and post-failure microstructural characterization. GNP incorporation generally reduced electrical resistance relative to neat cement, although the relative conductivity of the GNP-modified formulations varied with frequency, demonstrating that the concentration–conductivity relationship was not strictly monotonic. Under compressive loading, the 0.5 wt% powder-GNP specimen reached the highest UCS of 3885.1 psi, compared with 1499.6 psi for neat cement. The tested GNP-modified specimens also exhibited earlier electrical deviations relative to mechanical failure. Electromechanical warning times were 262 s for neat cement, 909 s for 0.3 wt% powder GNP, 570 s for 0.5 wt% powder GNP, and 1581 s for 0.5 wt% liquid GNP. The liquid-dispersed specimen therefore exhibited the longest warning interval and sustained electrical evolution throughout progressive deformation and post-peak degradation. These results demonstrate the feasibility of combining structural performance with intrinsic electrical sensing in practical wellbore-cement formulations. The study establishes an engineering framework for electrically responsive wellbore cement intended for geothermal, carbon-storage, hydrogen-storage, and long-term well-integrity monitoring applications.