Module 3 · Midstream: moving the barrel

Pipelines, blending and storage

Level 2 · Working knowledge 10 min read 4 questions

The moment a barrel enters a pipeline it usually stops being that barrel. Understanding common-stream blending, hubs and storage economics explains most of what looks strange about regional oil prices.

Between the wellhead and the refinery gate sits the midstream: gathering lines, trunk pipelines, tank farms, rail, barges and terminals. It is unglamorous, it captures a small share of the value of the chain, and it is where a startling amount of the risk lives.

Gathering, trunk lines and specifications

Small gathering lines collect from individual wells and batteries into a trunk line. To enter that trunk line the oil must meet a pipeline specification: limits on water and sediment, on vapour pressure, on viscosity, sometimes on sulfur and on total acid number. A producer whose barrel fails specification has no route to market at that point, regardless of what the barrel is worth in the abstract.

Common stream: your barrel is not your barrel

Most trunk pipelines run a common stream. Oil from many producers is commingled, and what arrives at the far end is a blend with the pipeline's own published quality, not any individual producer's crude. Quality banks settle the difference in cash: a producer who put in oil better than the stream average is credited, and one who put in worse is debited. The physical barrel ceases to be traceable; the commercial entitlement does not.

Some lines instead run batches, pushing discrete parcels of different grades one after another down the same pipe with a degree of mixing at the interfaces, which is cut out and downgraded. Batching preserves grade identity at the cost of throughput and complexity.

Hubs, and why storage has a price

Pipelines converge at hubs: places with many connections, large tankage and independent terminal operators. A hub is what makes a price assessment meaningful, because it is a place where many buyers and sellers can physically take or make delivery. That is why oil benchmarks are named after places and infrastructure rather than after countries - a point lesson 13 develops.

Tank farm

Fixed or floating-roof tanks, typically leased by the month. Floating roofs sit on the liquid surface to suppress vapour loss.

Working capacity

Usable volume, which is less than nameplate: tanks cannot be filled to the roof or emptied below the floating roof's landing point. Storage 'full' in the headlines usually means working capacity, not physical volume.

Line fill

The oil permanently inside a pipeline to keep it operating. It is inventory that can never be sold while the line runs, and it is a real capital cost.

Strategic reserves

Government-held crude, held for supply emergencies rather than for trading. See stockpiles and strategic reserves.

Contango, backwardation and the economics of a tank

Storage has a use whenever oil for future delivery is worth more than oil today. When the forward curve is in contango - future prices above spot - a trader can buy physical oil, sell a forward contract, pay for storage and financing, and lock in the difference. When the spread exceeds the full cost of storing and financing, tanks fill. When the curve is in backwardation - future below spot - holding inventory costs money, and the industry runs stocks down.

This is why inventory levels and the shape of the forward curve move together, and why a report that stocks are rising is not automatically bearish: it may simply be the curve paying someone to hold them. The direction of causation runs both ways and reading it as one-way is a common error.