Shell's grab of energy giant BG Group and a legal victory for frontier work offshore Alaska leaves rivals in the dust, though environmentalist are unimpressed.

The board of directors at Shell and BG group issued a joint statement last week saying they've reached an agreement for the Dutch acquisition of its British rival.

A weekend editorial from The Telegraph newspaper in London said the grab is an "audacious" move in a "new wave of oil industry consolidation" that's greeted a slump in oil prices that's lasted nearly a year. The deal, valued at around $70 billion, is among the largest acquisitions since the Exxon Mobil merger was completed in 1999.

For Shell, the acquisition may move the Dutch supermajor into the "pole position" as the largest oil company in the world. For rivals like BP, reeling from the dual financial blows of the Deepwater Horizon tragedy in 2010 and the low price of oil, it may be a sign of the writing on the wall, The Telegraph said.

BP ended 2014 with net debt of $22.6 billion. The company already announced plans to shed staff and, in February, Chief Executive Bob Dudley said the company is entering a reset phase focused on streamlined spending in the low oil price climate.

While its industry rivals shift gears, Shell is preparing to continue with drilling operations in the arctic waters off the coast of Alaska. The company already devoted about $5 billion and more than eight years of work on the campaign.

Last week, the federal Bureau of Ocean Energy Management said Shell's exploration plan is adequate for formal review.

Shell's plans were already the target of a legal challenge and, last week, activists from Greenpeace occupied the same rig chartered for earlier offshore Alaskan efforts.

"There is no compelling reason for the rush to give Shell another chance this summer," Susan Murray, deputy vice president for advocacy group Oceana, said in a statement.

Shell's plans for offshore Alaska are open for a public comment period that extends through April.