Poroelastic strain precursors during laboratory carbon dioxide core flooding revealed by helically bonded fiber sensing.

Reliable monitoring of carbon dioxide injection requires observations of both plume migration and the associated geomechanical deformation. Using a laboratory supercritical carbon dioxide core-flooding experiment, we show that circumferential strain measured by a helically bonded fiber evolves differently in space and time from carbon dioxide saturation imaged by time-lapse X-ray computed tomography. The associated coupled two-phase flow and poroelastic deformation modeling, constrained by the tomography-derived saturation data, indicates that strain changes precede the carbon dioxide saturation front as they closely follow pressure disturbances propagating through the connected water phase. Later strain evolution increasingly reflects capillary-controlled carbon dioxide invasion. Because pressure inside porous rock is difficult to measure directly at high spatial resolution, we interpret distributed strain as a model-constrained poroelastic proxy for the evolving pressure footprint. Overall, our results show that distributed strain sensing can identify mechanically affected regions ahead of the carbon dioxide plume front, when these measurements are supported by saturation imaging and sparse pressure gauge information.