Royal Dutch Shell said Monday it was closing some of the offices in the United Kingdom for BG Group as both companies move forward under a united structure.

British energy company BG Group became a unit within the corporate structure of Royal Dutch Shell in early February. The $7 billion tie-up was the largest of its kind since Exxon and Mobil joined forces in the 1990s.

Royal Dutch Shell said in a statement emailed to UPI that a December structural review of the combination was completed and, as a result, some regional offices of BG Group would close.

"One of the review's recommendations was to consolidate all Shell's London and South East based operations into Central London," Huibert Vigeveno, BG Group transition CEO, said.

While voluntary layoffs are opened to BG Group staff, all internal vacancies at Shell are now available to them. Employees who do leave would be counted under Shell's previous target of eliminating about 10,300 from its payroll.

Shell said combining with BG Group would mark the start of a new chapter for the company. Costs will move lower by about $4 billion for 2016, but also result in widespread redundancies. The Dutch supermajor said its full-year 2015 earnings declined 80 percent to $3.84 billion.

On a quarterly basis, BG reported a loss of $1.2 billion against $8.3 billion in the fourth quarter of 2014. Spending in its final quarter as a standalone company was 28 percent lower year-on-year at $1.7 billion, with nearly all of that targeting exploration and production.