BP has taken a final investment decision to move forward on its Mad Dog 2 project in the US Gulf of Mexico, a step made after years of reworking and cost-cutting that brought project costs down by more than half to $9 billion.

The final iteration of the new semi-submersible design will have capacity to produce 140,000 barrels per day of oil from up to 14 production wells, with planned first oil in late 2021.

“This announcement shows that big deep-water projects can still be economic in a low price environment in the US if they are designed in a smart and cost-effective way,” chief executive Bob Dudley said.

“It...