* Whitehaven says coking coal prices to stay high for months
* Company was not affected by Cyclone Debbie
* Looking to boost sales as some exporters face stalled operations (Adds background)
SYDNEY, April 13 (Reuters) - Australia's Whitehaven Coal Ltd said on Thursday that coking coal prices would remain high for months as supply disruptions since Cyclone Debbie damaged train lines and interrupted exports reverberate through markets.
Whitehaven, whose mines about 1,300 km (800 miles) south of the cyclone's path have been unaffected by the rail stoppages, also plans to boost its own coking coal sales next quarter as exporters further north grapple with stalled operations.
Five miners in the cyclone-hit region, including BHP Billiton and Glencore have declared force majeure - a clause typically invoked after natural disasters - since multiple landslides and flooding knocked out major coal rail networks.
Railway operator Aurizon is gradually returning some tracks to service. Its Blackwater line resumed operations on Monday and its Newlands line is expected to open on Thursday.
However, with the busiest Goonyella line further north closed until May, the disruption caused by the cyclone could lead to the potential loss of 15 million tonnes of coking and thermal coal exports from Australia, Whitehaven said in a statement on Thursday.
"This loss of exports is likely to be positive for coal prices until normal production and shipments resume and any contract delivery shortfall recovered, which could take some months," the company said.
Coking coal prices this month posted the biggest one-day surge on record as the rail outages blocked up to half the world's export shipments.
Spot prices on the Dalian Commodity Exchange, jumped more than 7 percent and Australian coking coal futures on the Singapore Exchange leapt 43 percent on news of the disruptions.
Whitehaven said customer requests for coking coal "increased substantially" since the storm and that the company expected to boost coking coal sales next quarter.
Whitehaven said it produced 5.7 million tonnes of coal for the quarter and affirmed its full-year production guidance of 21 to 22 million tonnes. (Reporting by Tom Westbrook; Editing by Eric Meijer and Joseph Radford)