Hen pecking at dirt where there was a heating fuel/oil spill! Wiped her soil-stained beak & very strong oil smell

[PandemicChicken]

One of my hens keeps getting into the area where heating fuel/oil spilled all over the ground a month ago. The ground was covered in leaves & I thought was frozen, but she managed to dig/peck her way through to reach the soft soil where there’s still oil residue/fuel that got absorbed into the soil. I wiped the dirt off her beak, and there was a strong oil smell on my hands/napkin. I tried opening her mouth to check if there was dirt inside, but I didn’t get a close look. Her beak kinda smells like oil/fuel too. I know when chickens peck around, sometimes they get dirt inside their mouth too. Is there anything I can do? Do you think the oil/heating fuel got ingested, or only on the outside of the beak??
Picture of my fluffy Henrietta!

 

[nuthatched]

Cover the area with a tarp or plywood, she should be ok.