Worldwide offshore oil and natural gas discoveries reached slightly below 2.3 billion boe last year, which was almost 90% lower than the resources uncovered in 2010, Rystad Energy said Wednesday.

In the Gulf of Mexico (GOM), however, the discovered volumes “remained relatively stable” compared to development in other global offshore regions.

Rystad said the global decline in offshore discoveries last year was “most significant” in the overall plunge in discovered volumes. Total global discovered volumes, oil and natural gas combined, fell to “an all-time low” from the 1940s, the Norwegian-based analyst said.

 In 2016, the average liquid content in the discovered resources was only about 40%.

“Even more tellingly, the replacement ratio for liquids in 2016 was below 10%,” analysts said. “For comparison, the replacement ratio for liquids in 2013 was as high as 30%.” The replacement ratio measures the amount of discovered resources during the year relative to the amount of liquids product in the same year globally, disregarding the production start-up date for the discoveries.

Discoveries in deepwater, which take years if not decades to develop, were not overwhelming in U.S. waters last year but the number remained stable, according to Rystad. Royal Dutch Shell plc has announced discoveries in the GOM, which are set to ramp up within the next few years. Anadarko Petroleum Corp. has development underway in several discoveries, as do ExxonMobil Corp. and others.

The Bureau of Ocean Energy Management’s Mike Celata, regional director of the GOM office, last August said the GOM “has proven to be one of the world's most prolific hydrocarbon basins and is the primary offshore source of hydrocarbons for the United States.” The federal Outer Continental Shelf "supplies the nation with approximately 97% of all offshore oil and natural gas production. Of both onshore and offshore domestic production in 2014, the Gulf supplied the nation with 16% of the total oil and 4.5% of the total gas."

The Energy Information Administration expected eight fields to come online in the GOM last year, with four starting up this year and two more ramping up in 2017, all signs that U.S. offshore output should hit record highs in 2017.

Rystad identified the key countries that influenced offshore discovered liquids development.

Brazil, said analysts, experienced a new “golden age,” because of multi-billion barrel discoveries made in the beginning of the decade.

Among the largest discoveries in Brazil, Lula (formerly known as Tupi), Libra and Buzios stand out, said Rystad. Combined, the discoveries hold 20 billion barrels of liquids. All of the large discoveries made in Brazil in the past decade are located in the large pre-salt basins, particularly Santos and Campos.

“However, the success story from 2010 did not repeat itself as 2016 approached” on a combination of factors, such as limited capital to develop projects that were previously discovered or local content regulations, among others.”

Offshore exploration on the Norwegian Continental Shelf was disappointing in 2015 and 2016, with no discovery surpassing 100 million barrels of discovered resources. Exploration results were considered “particularly discouraging given the number of exploration wells in the region, which remained relatively stable within the range of 45 to 65 exploration wells per year, since 2010.”

Meanwhile, Russia’s largest discovery in recent years was Universitetskaya, discovered in 2014. The discovery could potentially hold more than 2.3 billion bbl of resources, of which 1 billion bbl are liquids alone.

However, “Russia continues to be dependent on foreign technologies to be able to develop its offshore discoveries, especially in the arctic areas.” ExxonMobil struck an alliance with Russia’s OAO Rosneft in 2011 that included trading technology. “At the same time, exploration activities in offshore arctic regions are currently on hold” because of sanctions related to Russia’s Ukraine incursion “and generally less interest in the investment-heavy exploration” because of low commodity prices.

“Rystad Energy expects the exploration activity to slowly pick up from 2018, allowing for more discoveries toward the end of this decade and beyond,” analysts said. “At the same time, some of the recent license awards could open new prospective exploration regions, e.g. the deepwater license award in Mexico.”