The U.S. is overtaking Russia as the world's largest producer of oil and natural gas, a startling shift that is reshaping markets and eroding the clout of traditional energy-rich nations.

U.S. energy output has been surging in recent years, a comeback fueled by shale-rock formations of oil and natural gas that was unimaginable a decade ago. A Wall Street Journal analysis of global data shows that the U.S. is on track to pass Russia as the world's largest producer of oil and gas combined this year—if it hasn't already.

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