Rystad Energy estimates that liquid resources from mature assets grew 151 billion barrels over the last four years, which is almost 17% more than the amount produced in those years. This brings the total remaining liquid resource count to 1.227 trillion barrels as of year-end 2017.

Of the 151 billion increase, 68 billion barrels are from conventional onshore fields, 43 billion barrels are from shale, while offshore resources have grown by 40 billion barrels. For conventional onshore, a large part of the growth is driven by Saudi Arabia. Increased infill drilling and better investment terms have lifted the estimate for the remaining resources in the country. For shale, the growth is primarily driven by better well performance and more target benches in the Permian basin. The offshore uplift is driven by the Middle East, Russia and Europe.

“Growth in mature fields can be driven by many factors, such as increased infill drilling, improved understanding of the reservoirs, EOR projects and technology improvements. These developments are more challenging to track compared to new discoveries and often are difficult to measure,” Espen Erlingsen, senior vice president of upstream research at Rystad Energy, states.

The effect of these developments can be estimated by comparing the total amount of remaining resources in 2013 and 2017. The number was at 1.186 trillion barrels at the end of 2013. This was reduced through production by 132 billion barrels of oil and NGL. Over the same period 22 billion barrels of new liquid resources were discovered.

Those numbers indicate 1.076 trillion barrels should remain, but Rystad Energy’s latest estimates based on bottom-up research puts the count at 1.227 trillion barrels at the end of 2017, implying the 151 billion barrel growth from mature assets.

“Combining resource revisions in mature fields with volumes from new discoveries, 173 billion barrels were added to global resources over the last four years. The contribution from producing fields shows the importance of investing in mature assets,” Erlingsen comments.