During the period of soaking by ScCO2, ScCO2 continuously interacted with the reservoir rocks. To perform the effects of ScCO2 on the shales of the Nantun formation, clarifying the mechanisms of improving the shale oil recovery, the experiments for permeabilities were conducted in this article. The X-ray diffraction and Electron Microscopy Scanning（SEM ）were applied on the shales of the Nantun formation before and after soaking. Based on the analysis of the macroscopic and microscopic changes such as permeabilities, mineral compositions, surface morphology, and pore-throat structures, the results showed that after 7 and 14 days of soaking by ScCO2 solution, its permeabilities of the shales in the Nantun formation will be improved at about 1.6 times and 2.4 times, respectively. ScCO2 solution had significant effects of dissolution on dolomite and calcite, but it has no significant effects on the clay minerals, quartz and feldspar contained in the shales of the Nantun formation. At a micro-scale surface dissolution, after soaking by ScCO2 solution, the original pores were enlarged with corrosion or new pores were formed, resulting in the growth of permeabilities.
Yuze Zhang, Shangming Shi and Huabin Wei
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