* Four miles of ship channel shut by sunken boat
* Search continues for missing crewman
* Four crew members rescued by Lyondell workers (Adds details on ships waiting, expected duration of salvage, tug ownership)
By Erwin Seba
HOUSTON, Feb 11 (Reuters) - Two Houston refineries said their operations were unaffected on Thursday morning by the closure of a portion of the upper Houston Ship Channel due to a sunken tug boat and the search for a missing crewman.
Lyondell Basell’s [ACCELC.UL] 270,600 barrel-per-day Houston refinery is near where the tug sank in the Houston Ship Channel on Wednesday night. Valero Energy Corp’s (VLO.N) 145,000-bpd Houston refinery is west of the Lyondell plant.
The shutdown could extend into Saturday while the search for the missing crewman is conducted and the tugboat is removed, said Coast Guard Captain James Whitehead, deputy commander of Sector Houston-Galveston.
“The tugboat is partially blocking the channel,” Whitehead said at a news conference.
Two ships were prevented from coming into the upper channel and one ship was unable to exit on Thursday afternoon.
No ships were moving along a 4-mile (6.5-km) stretch at the beginning of the 53-mile (85-km) waterway between the Gulf of Mexico and the busiest U.S. petrochemical port, according to the Coast Guard.
Dock employees from the Lyondell refinery rescued four crew members from the tugboat J.R. Nichols when it sank at about 10:30 p.m. CST Wednesday (0430 GMT Thursday).
The tugboat is one of nine owned by a subsidiary of Kinder Morgan Energy Partners KMP.N.
“Our focus right now is on searching for the missing crew member,” said Emily Thompson, spokeswoman for Kinder Morgan Energy Partners.
A search continued on Thursday morning for a fifth crewman from the tug. The search must be completed before the tug can be taken from the channel.
The shutdown of a section of the channel was also intended to prevent the spread of fuel leaking from the tug along the waterway, the Coast Guard said.
All five Houston-area refineries are supplied with crude oil from tankers transiting the the Houston Ship Channel.
“The closure of the port will have no impact on our refinery operations at this time,” Lyondell spokesman David Harpole said in a statement.
Lyondell spokesman Aaron Woods said the company did not anticipate any impact on operations from the channel closure.
A Valero spokesman said the refinery was operating as planned.
“There are no known impacts at this time on operations at our Houston Refinery,” said Valero spokesman Steve Lee.
Editing by Lisa Shumaker