Krishnamurthy, Prasanna G. | Engineering Papers

DOE OSTI2022

Geologic Heterogeneity Controls on Trapping and Migration of CO 2

When CO 2 is injected into sedimentary basins, the fate of the buoyant CO 2 will be determined by how it interacts with the underlying geologic heterogeneities. Here we geologically print a cross-bedded pattern using two different bead sizes, and then conduct flow experiments to observe buoyant flow pathways, migration speed, and immobilized volumes. The amount of buoyant phase trapped under the heterogeneities is observed to vary by two orders of magnitude, with the controlling parameter being the size contrast between the coarse and fine grains that make up the structure. Furthermore, the results allow an estimate of heterogeneity trapping, and show how CO 2 trapping in aquifers can be experimentally evaluated before injection.

58 GEOSCIENCES↗

DOE OSTI2019

Mimicking Geologic Depositional Fabrics for Multiphase Flow Experiments

A novel laboratory technique is presented for generating two-dimensional beadpacks with reproducible natural geologic sedimentary bedforms. The heterogeneous beadpacks are deposited in a 0.6 m × 0.6 m × 0.02 m glass slab chamber using a programmable two-axis linear actuator. The method takes advantage of natural mechanical sorting processes, along with the ability to program the motion of the arm, to efficiently build cross-beds and ripple laminae similar to those seen in natural water-lain clastic deposits. By using a mixture of grain sizes (200 to 800 μm diameter), depositional fabrics with multiscale heterogeneity (mm to dm) are generated. Reproducibility tests show very high correlation among multiple fabric realizations produced with similar inputs. After introducing this first-of-a-kind capability to produce depositionally realistic fabrics at scales larger than that of rock cores, a demonstrative study is presented that illustrates gravity unstable multiphase flow which is relevant in the context of CO 2 sequestration. Preliminary results highlight the dramatic impact small scale capillary heterogeneities have on multiphase immiscible displacement and can help bridge understanding between core scale experiments and reservoir scale observations.

54 ENVIRONMENTAL SCIENCES↗