(Repeats earlier story for wider readership with no change to text.)
* BHP customer "not too worried" over strike given ample stocks
* Disruptions to pare 1.8 percent from 1Q supply -Goldman Sachs
* Big China, Japan smelters, have stockpiled 2-3 months supply
By Melanie Burton
MELBOURNE, Feb 15 (Reuters) - Even as strikes cripple output at the world's two biggest copper mines, Asia's copper industry is pretty relaxed, sitting atop metal stockpiles that have grown by nearly two-thirds since the end of January.
Copper inventories tied to China's Shanghai Futures Exchange have surged 61 percent since the week of Jan. 20 to 277,659 tonnes, the most since May 2016, the latest data shows. Stockpiles held in bonded warehouses in China have edged above 500,000 tonnes, from around 450,000 tonnes in November, according to consultants CRU Group.
BHP Billiton declared a force majeure last week on contracted copper shipments from its Escondida site in Chile, the world's largest copper mine, and Freeport-McMoRan Inc has sent home workers from its Grasberg facility, the world's second-biggest mine, this week.
But, because of the ample stockpiles, the outages have not worried the market as copper cathode premiums in China's bonded zones, what buyers will pay above global prices to procure the metal, remain steady at $75 a tonne. China is the world's biggest copper user. <0#BASEBW-SHMET>
"In China's bonded market there is still a lot of stock, so we are not that worried about the force majeure for now," said a BHP customer in Shanghai whose February shipments were delayed.
BHP halted its Escondida operations because of a worker's strike while Freeport closed Grasberg after filling up its on-site storage after a strike shuttered the smelter that is the only buyer of its copper output.
In addition to the high refined metal stockpiles, copper ore and concentrates imports to China swelled in the months before the disruptions. November imports were a record 1.76 million tonnes, with December just below that at 1.67 million tonnes, according to customs data.
While Chinese premiums remain steady, copper prices have surged, with three-month copper on the London Metal Exchange rising to $6,204 a tonne on Monday, the highest since May 25.
On the mine supply side, analysts estimate the disruptions will cut around 5,400 tonnes per day from the global supply of copper concentrate. If the Escondida strike lasts for 20 days, first-quarter global supply could drop 1.8 percent, according to Goldman Sachs.
In theory this could wipe out a small surplus of 80,000 tonnes of refined copper this year, estimated by analysts polled by Reuters.
Analysts at Standard Chartered said the loss of both Escondida and Grasberg is a "justified" bullish factor but they also note the high inventories.
"If sustained beyond the end of February then it is possible that the cathode market could... start to tighten. For the time being, though, we remain in a clear phase of cathode surplus," said the analysts in a report referring to the typical type of refined copper.
With the surge of concentrate imports, most Chinese smelters are in no rush for new supply.
"For the next two to three months most of the smelters are well prepared, particularly the main smelters. They were restocking the concentrate before Chinese New Year, so they are comfortable," said a source at a trade house in Shanghai.
Fees that smelters pay miners to process their concentrate, an indicator of the supply and demand balance, dipped to the mid$80's a tonne last week from the high $80s in mid-January, according to CRU.
JX Holdings Inc's metal unit, Japan’s biggest copper smelter, does not expect any impact from Escondida’s strike unless it dragged on for a few months, a spokesman said.
But Escondida could have ripple effects amid labour talks at other mines such as Rio Tinto's Kennecott mine in Utah. One trade house source in North America believes China has underestimated the strikes' impact.
"There is already a lot of enquires and some for as early as February. There seems to be a fair bit of appetite for Feb-March," the source said.
Reporting by Melanie Burton Additional reporting by Yuka Obayashi in Tokyo and Susan Taylor in Toronto.; Editing by Christian Schmollinger