Texas-based oil and natural gas company Apache Corporation received a takeover offer for over $18 billion by an unidentified party, Bloomberg reported, citing sources. The deal would be the biggest yet for an independent oil and gas producer in the U.S. this year, but Apache is said to have rejected the initial offer and is currently working on defense with Goldman Sachs Group.

In July, Noble Energy Inc. took over Texas shale driller Rosetta Resources Inc. for $3.9 billion in an all-stock transaction, including the assumed debt. 

It was not clear if there would be any further talks regarding the Apache takeover. Apache has a shale play in the Permian Basin in western Texas, which is one of the company’s biggest leaseholders. The Texas shale play is the only one where oil output has been growing while drillers cut their expenditure and let go of idle rigs, Bloomberg reported.

The company also explores in Egypt, the Gulf of Mexico and Canada. In the U.S., Apache has the Eagle Ford in southern Texas and Woodford shale in Oklahoma for exploration, Bloomberg reported.

Apache posted a smaller-than-expected adjusted loss Thursday and increased its production forecast. The company posted a net loss of about $5.7 million for the third quarter, compared to a loss of nearly 1.3 million during the same period last year, Bloomberg reported. It also slashed its capital budget for 2015 by over 60 percent, as compared to the previous year.

A major producer during the 2000 shale boom, Apache has underperformed in recent years. The Bloomberg report cited investments in failed projects in Argentina and Australia as a reason for the losses, adding that the company has started selling stale projects in Australia and Texas. In January, the company appointed John J. Christmann as its CEO.

Stocks of Apache, which has been facing the brunt of falling crude prices along with many other players in the field, have reportedly fallen 54 percent since peaking in 2014. The S&P index of 17 drillers has fallen 28 percent over the last year.