Shale drillers in the Permian Basin are producing vast amounts of gas as a byproduct of prospecting for oil. But there aren’t enough pipelines to take all the gas to market, causing some of it to become landlocked, and sending local prices into free fall. Gas prices in parts of the prolific region hovered near zero last month and some trades went negative, to as low as a negative 25 cents per million British thermal units, according to S&P Global Platts. The price-reporting agency said it was the first time on record that gas traded for less than zero at the Waha hub in West Texas. While prices have since ticked up, averaging $1.68 per million British thermal units for the four weeks through Dec. 21, that is still 40% of the $4.20 per million British thermal units that gas has fetched in that time at the main U.S. […]