Expected to be completed in 2016, the agreement is subject to further approvals from company shareholders and regulatory authorities in the countries BG operates in, including the European Union, China, Australia and Brazil.
Shell CEO Ben van Beurden said: "We’re well underway with the anti-trust and regulatory filing processes in relevant jurisdictions around the world and we’re confident that, following the usual thorough and professional review by the relevant authorities, the deal will receive the necessary approvals."
As part of the deal, Shell will purchase BG’s liquefied natural gas (LNG) business as well as its projects in Brazil, East Africa, Australia, Kazakhstan and Egypt.
BG CEO Helge Lund earlier said: "BG’s deep water positions and strengths in exploration, liquefaction and LNG shipping and marketing will combine well with Shell’s scale, development expertise and financial strength.
"The consolidated business will be strongly placed to develop the growth projects in BG’s portfolio.