ONE way of helping to reduce emissions of carbon dioxide into the atmosphere is to pump the gas into underground caverns or old oil fields.

The easily available oil from West Texas’s Permian Basin, the richest oilfield in America, is mostly gone now. The best way to extract the remainder is to pump gas down to force the oil out.

When the price of oil is low, exploration and production is expensive, but companies can rely on retail assets such as gas stations to benefit from the high profit margins at the pump.