BP started the formation of "Super Majors" with it's acquisition of Amoco, followed by Arco. Not to be left behind, Exxon acquired Mobil, Chevron took over Texaco, and smaller mergers followed such as ConocoPhillips.
You can Google John Browne to find out what led to his downfall at BP, whose biggest legacy of ruthless cost cutting led to numerous accidents at BP owned facilities, and most likely set the culture that led to the latest disaster in the Gulf of Mexico.
Below, in its entirety is the April 2001 Forbes article, "Going Deep" written by Daniel Fisher. (Clicking on the picture will enlarge it for easier reading...)
And just in case you were curious about historical crude oil prices and BP's stock price, here they are...