Oil futures finished lower Monday, with the U.S. benchmark pulling back from a more-than-three-year high as a weekly increase in the number of rigs drilling for oil in the U.S. fed expectations for a continued rise in domestic production.

Natural-gas prices, meanwhile, saw volatile trading, with the February futures contract settling sharply higher just ahead of its expiration. On the New York Mercantile Exchange, March West Texas Intermediate crude fell 58 cents, or 0.9%, to settle at $65.56 a barrel. Prices settled Friday at their highest since December 2014. March Brent crude the global benchmark, lost $1.06, or 1.5%, to$69.46 a barrel on the ICE Futures Europe exchange.

The U.S. oil rig count rose by 12 in the week ended Jan 19, bringing the total to 759, the highest since August, according to a weekly report released Friday by oil-field services firm Baker Hughes Inc. The rig count is generally viewed as a proxy for activity in the sector. Last week’s oil-rig increase marked the “biggest gain since last March and oil drilling activity is the highest since Sept. 1—and only 8 rigs shy of last year’s high on Aug. 11,” said James Williams, energy economist at WTRG Economics. “What should get some more attention is that there was an 18-rig gain in the Permian Basin, putting drilling activity in West Texas and Eastern New Mexico (Permian) at the highest level since January 2015,” he said.

Last week, U.S. Energy Information Administration data revealed that crude inventories have fallen for 10 straight weeks, but crude output rose by 128,000 barrels a day to 9.878 million barrels a day in the week ended Jan 19, according to the EIA. Oil market observers will be looking ahead to the EIA’s report this coming Wednesday, which will offer a fresh view on U.S. crude output and supplies. Traders will also continue to keep an eye on developments in Venezuela, as the country “remains the single greatest risk for a major supply interruption,” said Williams. OPEC member Venezuela suffers from an economic crisis as well as political turmoil. “If there is a total halt [to] Venezuelan oil exports, OPEC will increase production to compensate—but it takes a month or more, so there will be a spike in prices until other supplies are in the market,” Williams said.

Among other energy contracts, February gasoline slipped 0.1% to $1.935 a gallon, while February heating oil lost 1.5% to $2.105 a gallon. February natural gas which expired at the day’s settlement, jumped 12.6 cents, or 3.6%, to end at $3.631 per million British thermal units. The contract rose about 10% last week, after a midweek move that sent it to a Dec. 30, 2016 high on bets of cold weather to come in February. But March natural gas which is now the front-month contract, settled at $3.167, down less than a penny, or nearly 0.3%, on Monday. The big difference between the two contracts is timing of the delivery,” explained Williams. “If you bought the February futures contract and held it until expiration, then the seller must deliver that gas to you at the Henry Hub in February,” he said. But “stocks of gas in storage are low, in some areas the lowest in over five years, and colder-than-normal weather is expected in the next couple of weeks.” “By March, we don’t know the weather outlook and the demand is [usually] lower at that time,” he said, so March prices are lower.