A long period of low oil prices has saved motorists money at the pump, but languishing crude prices could drive up heating bills. That is because the natural-gas supply is closely connected to oil drilling. Low crude prices have led U.S. oil producers to idle more than a thousand rigs over the past two years, resulting in a big decline in so-called associated gas, a byproduct of oil drilling. This gas typically represents about 40% of total supply, but its production isn’t particularly responsive to gas prices. Since September 2015, associated-gas production outside the Northeast, the country’s fastest-growing gas-producing region, has fallen by nearly 9%, or about 2.5 billion cubic feet a day, according to energy data firm Platts Analytics Bentek. That drop-off is enough to fuel roughly 13 million U.S. homes daily, and one reason monthly heating costs are poised to rise. Natural gas heats about half of […]