Crude oil marginal production costs per barrel by country

What are the crude oil marginal production costs in top oil producing countries ?

The marginal production costs of crude oil depend also on the oil extraction method. There are different costs related to onshore production, offshore production, production from oil shales etc. But in general, some countries can produce oil with lower average costs and other with higher average costs.

For example:
Saudi Arabia, Iraq, Iran - can produce oil with really low costs, for around 10 USD per barrel
Russia - can produce oil with relatively low costs, for around 20 USD per barrel
US - can produce non-shale oil with relatively low costs and shale oil with higher costs
China, Mexico - can produce oil with higher costs
Brazil, United Kingdom - can produce oil with quite higher costs

Total production price depends on costs related to oil extraction, transportation and storage of oil, taxes etc. If one or more of these costs are low, it makes an advantage.