It's not oil prices, but extreme winter weather that's impacting production and drilling operations in the Permian shale oil basin in Texas, an operator said.

Pioneer Natural Resources said severe winter weather in West Texas has left the Spraberry/Wolfcamp area in the Permian basin in the dark and out of reach. The company said an "extensive recovery period is expected," and it could take several weeks before it determines the full extent of the damage.

The National Weather Service said Wednesday conditions are ripe in West Texas for a possible winter storm and accumulations of freezing rain. The high for Wednesday is predicted at 31 degrees Fahrenheit, about 30 degrees below average.

Since the start of the year, Pioneer said much of the associated infrastructure in the Spraberry/Wolfcamp area is frozen over.

According to Pioneer, the Spraberry/Wolfcamp resource area is behind the steady growth in the Permian basin in western Texas. The company estimates the area contains more than 75 billion barrels of oil equivalent.

"This ranks it as the largest U.S. oil field and the second largest oil field in the world," the company said.