How do we know that these oil companies are telling the truth about the discovered amount?

If the new Prez has his way, we'll be shovelling coal in our tanks.

The biggest problem facing Mexico’s much diminished oil giant, Pemex, in 2017 will be finding a way to service a growing debt pile of over $100 billion – most of it denominated in foreign currency – from the proceeds of a continually shrinking revenue base.

Btw, their oil production is at 26 year low.

Well, he don't have much options. And volcano part has not much use here.

Mexico’s existing oil reserves are dwindling so fast the country could go dry within nine years without new discoveries.

That’s the message from the National Hydrocarbons Commission, which said Friday that the reserves fell 10.6 percent to 9.16 billion barrels in 2016, from 10.24 billion barrels a year earlier. Once the world’s third largest crude producer, Mexico’s proven reserves have declined 34 percent since 2013.

He set 8.9 years as a time frame for the reserves to run out.

Sad truth.

https://www.bloomberg.com/news/articles/2017-03-31/down-10-mexico-oil-reserves-gone-in-9-years-without-new-finds

@brianl

Looking at Mexica and Brazil internal economic and political things it is clearly not the case.

Recent rate of commercial volumes found gives little confidence that there will be enough new discoveries to fill the gap. Spend on exploration globally has collapsed from US$60 bn p.a. in 2014 to just US$25 bn p.a. in 2018. The drop has fed directly through to significantly lower volumes of reserves discovered. Exploration found 8 bn bbls p.a. of commercial liquids on average in the early part of this decade; it’s only delivered around 2 bn bbls p.a. in the three years since 2014.

The oil market could be running short of oil capacity by the late-2020s at the current, low discovery rate. That’s worryingly near at hand given it takes the best part of 10 years for the average new discovery to build to peak production even with a marked improvement in project execution post-downturn. Should new volumes discovered recover to pre-crash levels of 8 bn bbls p.a. the gap opens up in the early 2030s and climbs to 6 million b/d by 2040. This will have to be filled by presently sub-commercial discoveries with implications for price.

https://www.woodmac.com/news/the-edge/the-case-for-investing-more-in-exploration/

There's enough to last 55 years, by then the world will be smitten with panels.