1983, NYMEX (the New York Mercantile Exchange) launched the light sweet crude oil futures contract. This is commonly known as WTI crude oil futures. As the United States is the world's largest energy consumer, and NYMEX's WTI crude oil futures are the most active crude oil trading varieties, WTI crude oil prices are gradually used to explain "international crude oil prices".
According to the British financial situation, the lowest historical price of WTI crude oil was 9.75 USD/barrel, which appeared in1April, 986.
References:
British finance: WTI crude oil price