Trailers work with unrefined oil. There isn’t much difference between a truck trailer and an oil tanker car on the railway.

Difference is size and cost per unit to move it. We are talking about Middle East light sweet crude oil here, not Alberta’s oil sands or whatnot which does require some processing and heating even before sending it through a pipeline.

North Dakota currently sends a few trainloads of crude oil directly from the fields to refiners 50 miles away from me today. Tanker trucks do routes picking up a few dozen barrels per rig every few days/weeks/months in low producing areas of the country.