Flow visualization of <scp>CO₂</scp> in tight shale formations at reservoir conditions

Abstract

Abstract The flow of CO 2 in porous media is fundamental to many engineering applications and geophysical processes. Yet detailed CO 2 flow visualization remains challenging. We address this problem via positron emission tomography using 11 C nuclides and apply it to tight formations—a difficult but relevant rock type to investigate. The results represent an important technical advancement for visualization and quantification of flow properties in ultratight rocks and allowed us to observe that local rock structure in a layered, reservoir shale ( K = 0.74 µdarcy) sample dictated the CO 2 flow path by the presence of high‐density layers. Diffusive transport of CO 2 in a fractured sample (high‐permeable sandstone) was also visualized, and an effective diffusion coefficient ( D i = 2.2 · 10 −8 m 2 /s) was derived directly from the dynamic distribution of CO 2 . During CO 2 injection tests for oil recovery from a reservoir shale sample we observed a recovery factor of R F = 55% of oil in place without fracturing the sample.