One of the most favored and sophisticated trades among oil market players is the WTI/Brent box, which, in brokers’ slang, is often referred to as the “puzzle.” It involves the simultaneous purchase and sale of Brent spreads against WTI spreads. Alternatively, viewed from a different angle but arriving at the same result, it entails buying and selling shorter-dated versus longer-dated arbitrage. In practice, this trade predominantly takes the form of time spreads or arbitrages six months apart, preferably June/December or December/June.

It is an exotic trade, as it reflects a comprehensive market view of the comparative strength or weakness of the two major crude oil benchmarks. It captures the underlying supply and demand for these grades, together with transatlantic shipping costs and even refining margins. It goes without saying that geopolitical events can, and do, greatly influence the value of the “puzzle,” as illustrated in the accompanying chart.

The recent and sudden weakness of this structure is clearly discernible. It began at the start of 2026 and can be attributed to three developments: Venezuela, Ukraine and Iran, along with their respective effects on the factors that influence the price of a barrel.

After the capture of the former Venezuelan president and the reshaping of the country’s oil industry at the beginning of the new year, expectations of fierce competition between the Latin American country and Canada—both suppliers of heavier and more sour crude oil, the preferred staple of U.S. refiners—increased. This put downward pressure on domestic grades, including WTI, due to the increasing availability of U.S.-produced crude oil. Whether Venezuela will prove to be a long-term and reliable exporter of crude oil to the U.S. remains questionable and is yet to be seen.

Meanwhile, accurate Ukrainian drone strikes on Russian oil facilities, such as pipelines, ports and refineries, continued without interruption. Coupled with effective U.S. sanctions, which restricted Russia’s ability to export freely, these developments significantly supported diesel and European crude oil prices.

Last, but certainly not least, the joint U.S.–Israeli assault on Iran and the consequent retaliatory measures by the Persian Gulf OPEC nation targeting the region’s oil and gas fields, refineries and the critical Strait of Hormuz shipping lane—which, in peaceful times, allows 20 mbpd of oil to sail through—sent the price of oil to levels not seen since July 2024. Fears of severe supply disruption were exacerbated by the astronomical rise in freight rates and insurance costs.

The collective impact of these geopolitical developments was a nearly unprecedented plunge in the June 26/December 26 WTI/Brent box, which fell to -$1.60/bbl by March 3. These events are likely to shape its movement for weeks to come and beyond. No doubt, by the time this Insight is published, the market will have changed considerably. As the situation around these geopolitical hotspots evolves, the value of the “puzzle” aligns accordingly. It is a logical and, more importantly, safe way to express one’s view on how perceived and actual conflicts influence the underlying oil balance. Despite the complexity of this four-legged trade, it remains a highly efficient way to express a macro view on the crude balance, especially given the robust liquidity of CL/BZ box instruments. For seamless execution, these structures are fully available on CME Direct, allowing you to manage exposure to these global shifts without the high transaction costs typically associated with multi-leg positions.