Strikes at two Colombian producers since earlier this month and an export ban at a third mine could mean the world's fourth largest exporter loses almost 3 million tonnes of production for February unless there is a resolution soon, calculations by Reuters and analysts suggest.
That figure - equivalent to the amount of thermal coal Germany imports in an average month - would be expected to lead to a jump in prices during times of economic growth.
But the apparent global abundance of coal and weak demand in key markets may mean buyers have been cushioned from big price rises despite multiple disruptions to shipments, analysts said.
Prompt deliveries of coal into northern European ports are trading just below $90 a tonne, just a few dollars above their levels before the main Colombian strike began on Feb.7, while API2 coal swaps for 2014 delivery on Friday settled near $99/tonne, $3 above levels at the start of this year.
Other problems hitting coal exporters have failed to drive up coal swaps.
"We have already seen torrential monsoon rains in Indonesia, a strike in New South Wales, cyclone-related disruptions in Queensland and no big consequence (for prices)," said Carlos Fernandez Alvarez, a coal analyst with the International Energy Agency.
"So probably that feeling of oversupply is more than a feeling," he added.
Earlier this week traders at some utilities that buy from Colombia said the market would start to get nervous if supply disruptions continued into next month.
Colombia's thermal coal exports of 77.4 million tonnes last year accounted for around 10 percent of total global seaborne supply.
"That prices have not moved at all, apart from a $2.50 up and down move on the back of strike news at the Cerrejon mine (Colombia's largest), reveals that the market was oversupplied by a great amount," said an analyst with a trading house who requested anonymity.
Based on national import figures, the Latin American country accounts for around 30 percent of imports in Britain, Germany, Turkey and Spain, which between them took delivery of around 32 million tonnes of Colombian coal in 2012, the analyst said.
Israel, Chile and the United States account for a further 16 million tonnes of demand for Colombia's coal, meaning customers will need to source alternative supplies, defer shipments or draw down stocks if production problems persist into next month.
Demand for coal in Europe tends to ease in the second quarter as the northern hemisphere moves into spring, although from the start of March stockpiles are likely show a major drop because of the cancelled shipments from Colombia, analysts said.
Around 2.5 million tonnes of coal is stored at Rotterdam's coal terminal, up 500,000 from the end of last year, and the figures will start to fall at the time when Colombian shipments would have completed their voyages to European ports.
Between them utilities in northern Europe and the Mediterranean are estimated to import around one capesized vessel (150,000 tonnes) of Colombian coal a day on average.
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The strike at Colombia's largest producer Cerrejon, a joint venture between Anglo American BHP Billton and Xstrata, is now in its third week, costing the company around 100,000 tonnes in lost production a day.
This has prompted default on some of the mine's shipments and the cancellation of orders by power generators.
On Friday, the main union at the mine said it would re-enter preliminary talks with management but will only deal with the logistics of re-starting wage negotiations.
Meanwhile an export ban imposed by the government for environmental reasons on Drummond, Colombia's second biggest producer, prompted the company to slash daily production of around 80,000 by three-quarters from Thursday after stocks reached maximum capacity.
A third producer, La Francia, is losing 15,000-20,000 tonnes a day of production because of a strike.
Taken together, the stoppages would cost Colombia 4.5 million tonnes a month in lost production, according to analysts.