The relentless drilling ramp-up in America’s top shale plays is making investors more skeptical that an oil price rebound is on the horizon. After increasing their bets on rising West Texas Intermediate crude for three straight weeks, money managers slashed the wagers by 21 percent, according to U.S. Commodity Futures Trading Commission data. Producers in Texas are leading the longest shale revival since 2011, making OPEC-led efforts to rebalance the market increasingly difficult. After the year started on a bullish note, with prices in New York topping $55 a barrel as Saudi Arabia, Russia and other major exporters began to cut production, the rally has staggered. Saudi Arabia’s Energy Minister Khalid Al-Falih has admitted the first three months of supply curbs failed to bring inventories below the five-year average. As optimists lose heart, prices fell back below $50 last month. There’s still a lot of talk about high inventory levels, Michael Lynch, president of Strategic Energy & Economic Research in Winchester, Massachusetts, said by telephone. Investors felt that prices had “gone up too much compared to the fundamentals. The shale oil production trend is definitely bullish, which is bearish for prices.” This month’s production in the top U.S. shale plays will reach about 5.2 million barrels a day, the highest level since November 2015, according to the Energy Information Administration. As producers pour billions of dollars of investment into fields like the Permian and Eagle Ford in Texas, the country’s oil-rig count has more than doubled in a year to 697 last week, according to Baker Hughes Inc.