* Oil spillage from cracked pipelines; none from tanker
* Tanker suspected to have approached at higher than recommended speed
* Cleanup for seashore seen to take up to two weeks
* No refinery production impact from the incident
* Ocean Tankers says to discuss with Shell over unloading
By Meeyoung Cho and Keith Wallis
SEOUL/SINGAPORE, Feb 3 (Reuters) - Teams of workers, aided by ships and aircraft, will complete on Monday the sea cleanup of 164,000 litres of oil that leaked off South Korea's southern coast, the coast guard said, after a pipeline run by GS Caltex Corp cracked at the weekend.
A cleanup of shore areas will take up to two weeks.
The crack and subsequent leak occurred on Friday at a quay off Yeosu, more than 300 km (185 miles) south of Seoul, while the 318,445 deadweight tonne Very Large Crude Carrier Wu Yi San was preparing to berth and offload crude.
Oil remaining in the pipeline leaked, but none spilled from the tanker, which did not hit refinery production at GS Caltex, according to the refiner and the Korea Coast guard.
"A clean up would be completed within today, while a clean up of the seashore would take one or two weeks," a senior official at the Yeosu Coast Guard of Korea told a press briefing broadcast live on television.
The prime minister's office, in a statement issued on Sunday, said an oil boom to control the spillage would be expanded to a diameter of 9.5 km from 5 km, and 201 vessels and five planes would work on the clean up.
The coast guard official said the tanker was suspected of approaching the quay at a higher than recommended speed, but the exact cause of the accident was under investigation.
He added that crude oil, naphtha and other oil compounds leaked from three cracked pipelines at the quay.
The tanker is operated and managed by Singapore's Ocean Tankers, which said the vessel was under the control of two port pilots and assisted by five harbour tugs when it struck the shore jetty and pipeline.
Surveyors from ship safety classification society ABS and the ship's insurer, the North of England P&I Association, are helping the investigation and assessing damage to the ship, said Ng Kwang Chiau, senior vice president at Ocean Tankers' fleet management division.
He said the ship's voyage data recorder, or "black box", would be analysed as part of the investigation.
There were no injuries to the crew, Ng said. The front of the ship sustained minor damage, but the vessel was safely anchored.
The ship was chartered to Shell, Ng said and talks would take place with the oil major about unloading options, he told Reuters.
A spokesman at GS Caltex said: "The tanker needs to go through safety tests before unloading the crude and unloading might be done through a jetty nearby or ship-to-ship, which the shipper is in charge of."
He declined to comment on the type of the crude in the tanker.
South Korea's second-largest refiner, with a 775,000-barrels-per-day (bpd) capacity, GS Caltex is equally owned by Chevron Corp, the second-largest U.S. oil company, and South Korea's GS Energy, owned by GS Holdings .
In 2007, South Korea's worst oil spill occurred off the coast of Taean, when 10,500 metric tonnes spilled from a Hong Kong-registered tanker whose hull was punctured in a collision.
In November 2013, a small amount of oil leaked into the sea east of South Korea from a cracked pipeline run by the country's top refiner, SK Energy, owned by SK Innovation.