International oil and gas exploration and production company Occidental Petroleum has completed its previously announced acquisition of Anadarko Petroleum in a $55bn deal.

Proposed in April, the transaction also includes the assumption of Anadarko’s debt.

Occidental Petroleum president and CEO Vicki Hollub said: “With Anadarko’s world-class asset portfolio now officially part of Occidental, we begin our work to integrate our two companies and unlock the significant value of this combination for shareholders.

“We expect to deliver at least $3.5bn annually in cost and capital spending synergies and the focus of our board and management team is on execution to achieve the promise of this exciting combination.”

The transaction was closed after it was approved by the shareholders of Anadarko at a meeting, where more than 99% of the shares voted were in favour of the Occidental merger agreement.

As part of the acquisition, Anadarko shareholders are receiving $59 in cash and 0.2934 shares of Occidental common stock per share of the former’s common stock in the transaction.

Occidental’s midstream and marketing segment purchases, markets, gathers, processes, transports and stores hydrocarbons and other commodities.

Occidental secured the acquisition of Anadarko Petroleum in May after Chevron decided not to increase its initial offer to counter Occidental’s bid.