Energy stocks only kept pace with broader markets on Monday, Sept. 18, after days of leading them higher. 

U.S. oil prices fell below $50 a barrel again on Monday amid reports Royal Dutch Shell (RDS.A)  had restarted a key Houston refinery that was shuttered by Hurricane Harvey three weeks ago. Refineries in the region are slowly coming back online, meaning that mushrooming crude stockpiles can be processed and delivered to markets.

Houston-based energy services firm Baker Hughes reported on Friday that U.S. oil and gas producers took eight rigs offline during the past week, bringing the Houston oilfield services provider's total count to 936, the lowest since June. They also indicated that the oil-rig count decreased by seven from the previous week to 749, while the natural gas rig count fell by one to 186 and the U.S. offshore rig count rose marginally.

West Texas Intermediate crude was down 0.3% to $49.73 a barrel on Monday morning.

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A crude oil rally last week pulled the commodity to its highest level in roughly a month and a half after signs of reduced global production. Global oil supplies have hit a snag as Hurricane Harvey limited output in the U.S. and declining activity in the Middle East helped the Organization of Petroleum Exporting Countries maintain a previous deal to limit production.

Energy gains were roughly in line with other sectors' increases on Monday morning. Major oilers Exxon Mobil Corp. (XOM) - Get Exxon Mobil Corporation Report , Royal Dutch Shell, Total SA (TOT) - Get Total SA Sponsored ADR Class B Report , and China Petroleum & Chemical Corp. (SNP) - Get China Petroleum & Chemical Corporation Sponsored ADR Class H Report were lower, while Chevron Corp. (CVX) - Get Chevron Corporation Report , PetroChina Co. Ltd. (PTR) - Get PetroChina Company Limited Sponsored ADR Report , and Schlumberger Ltd. (SLB) - Get Schlumberger NV Report climbed. 

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