Apache said the stock and cash deal valued Mariner's common stock at $26.22 per share, a 45 percent premium over its Wednesday closing price. Mariner shareholders would receive 0.17 of an Apache share and $7.80 for each Mariner share.
The company also said it would assume $1.2 billion in Mariner's debt as part of the deal, and that the transaction might be completed by the third quarter.
Apache has been on the prowl for well-priced oil and gas properties that fit neatly into its existing exploration program.
On April 12, it said it planned to buy Devon Energy Corp's
Shares of Apache closed at $108.06 Wednesday on the New York Stock Exchange. Shares of Mariner were trading 41 percent up at $25.5 in trading before the bell on Thursday.
(Reporting by Arup Roychoudhury in Bangalore; Editing by Jarshad Kakkrakandy)