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I suspect that the author just picked some numbers out of some press release or something without having any idea what they mean. Reserve estimates have fairly well defined classifications and they mentioned no classifications at all in the article.
Basically there are estimates of hydrocarbons (HC) in place, as well as proved, developed, undeveloped, unproved, possible and probable reserve categories. The difference is whether one thinks there is a 10% chance of producing them and not a lot of corroborating information (a very high number!) or a 90% chance of producing them and a lot more information (a much more conservative estimate). Since many rock properties (i.e. permeability, fracture intensity) tend to have a log-normal distribution, there can be very long tails on the distribution of reserve estimates when properties are uncertain. For log-normal distributions it is fairly common to have a standard deviation that is larger than the mean value.
You can rest assured that the author of that article had no idea what parameters were being used or what they meant, or they would have mentioned them. However, it's much easier to baffle with bullsh*t rather than understand things.
CQ de W5ALT
Walt Fair, Jr., P. E. Comport Computing Specializing in Technical Engineering Software