A major oil and natural gas project expansion in the deepwater Gulf of Mexico (GOM) has ramped up four months ahead of schedule and 15% under budget, BP plc said Thursday.

The  Thunder Horse Northwest Expansion is expected to boost production at the massive Thunder Horse facility by an estimated 30,000 boe/d at its peak, taking gross output at one of the largest oilfields in the GOM to more than 200,000 boe/d.

The northwest expansion initially was scheduled to start up early next year.

“Our business in the Gulf of Mexico demonstrates our upstream strategy in action,” said upstream CEO Bernard Looney. “Leveraging our world-class position and facilities, we are bringing new barrels online rapidly and efficiently, and uncovering more opportunities nearby. We are focused on growing value and these projects in the Gulf are competitive with any opportunities we have worldwide. This is what we mean by growing ‘advantaged’ oil.”

CEO Bob Dudley earlier this month said BP needed to continue investing, “not to find and produce as much as we can, but to access the most advantaged new barrels that will be needed to make up for declines.”

The Thunder Horse field was discovered in Mississippi Canyon in 1999, and it is 75% owned by BP and 25% by ExxonMobil Corp. The platform, which sits in more than 6,000 feet of water about 150 miles southeast of New Orleans, has capacity to handle 250,000 b/d gross oil and 200 MMcf/d gross natural gas.

Thunder Horse initially began producing in June 2008 and at the time it started up, the platform was considered the largest oil and gas producer in the GOM.

The latest expansion is the fourth global upstream endeavor year-to-date by BP to begin producing, following seven global start ups in 2017 and six in 2016. New BP-led projects scheduled to start operations between 2016 and 2021 are forecast to provide the supermajor with another 900,000 boe/d of production by 2021.

“This latest expansion of Thunder Horse is another important milestone in our efforts to maximize value from our assets in the Gulf,” said BP’s Starlee Sykes, regional president of GOM and Canada business. “Over the past five years we’ve driven up production through safe and reliable operations and bringing on new deepwater projects in a more efficient and standardized way. All this hard work is now delivering results. Our Gulf of Mexico business is thriving.”

The expansion, which achieved first oil and gas only 16 months after being sanctioned, includes an additional subsea manifold and two wells tied into existing flowlines two miles to the north of the Thunder Horse platform.

In 2017, an expansion of Thunder Horse’s south field, a four well tie-back to the floating hub, boosted gross production by more than 50,000 boe/d. And in 2016, BP started up a major water injection project at Thunder Horse to further enhance oil production.

BP operates three other large GOM production platforms in Atlantis, Mad Dog and Na Kika, and it holds stakes in four nonoperated hubs -- Mars, Olympus, Ursa and Great White.

In the past five years, BP’s average output in the GOM has increased on average to more than 300,000 boe/d from under 200,000 boe/d in 2013. More output is expected from various expansions, including the estimated $9 billion Mad Dog Phase 2 deepwater expansion in Green Canyon blocks, which is slated for completion in 2021.

BP altogether holds acreage in about 200 lease blocks in the GOM. Other global upstream efforts that have ramped up for BP this year are the natural gas project Shah Deniz 2 in Azerbaijan, Atoll in Egypt and the Taas expansion in Russia.