back-up isn't just an IT issue
"the ransomware KO'd back-office systems used for monitoring oil flows and generating billing records based on those flows"
That shouldn't be a reason to shut down completely. There should be some back-up means of measuring quantities, may be less accurate and you might lose a profit margin, but better to do that and keep things flowing and save on the ransom. For example, if the oil comes from or goes into storage tanks (which it probably does), then send someone out to read the level gauges on the tanks before and after, take a photo perhaps, write out the bill by hand if necessary. Point out to customers they have a choice of delivery charged on that basis or no delivery at all.
On parallel lines , my local supermarket once had all the barcode scanning equipment down. To keep things moving and probably prevent a riot, the check out staff were authorised to assess the value of each shopping trolley by sight and propose a price , if the customer disagreed , they got out the pen and paper. Sure , they must have lost something, but they didn't throw away perishables as unsold, and all the customers were happy in getting their dinners as normal.