BG Group PLC says it is in "advanced discussions" with Royal Dutch Shell PLC about a possible offer from Shell to buy the British natural gas producer.
The company said late Tuesday that there is no certainty that a deal will be struck. It gave no further details.
Representatives for Shell, which is Europe's largest oil company by market value, declined to comment.
The statement from BG Group followed a Wall Street Journal report that said the deal could be valued at around $50 billion.
Energy companies are looking to reduce costs and become more efficient in the wake of tumbling oil prices. One route is through consolidation.
Last November, Halliburton said it would pay $34.6 billion for rival oilfield services company Baker Hughes.