* Short-lived stoppage did not affect refining operations
* Workers obtain pay increases upwards of 40 percent
* Expansion project will more than double capacity
BOGOTA, Sept 23 (Reuters) - Construction workers were due to return to work at Colombia's Cartagena oil refinery later on Monday after agreeing to a pay increase, their union said, a deal that ends a three-day strike that did not affect refining operations.
U.S.-listed CB&I, or Chicago Bridge and Iron Co, a third-party contractor in charge of a $6.47 billion expansion will increase wages between 40 and 100 percent, said Rodolfo Vecino, head of the USO oil industry labor union.
The refinery, Reficar, fully-owned by Colombia's state-run oil company Ecopetrol will raise refining capacity on completion of the project in 2015, to 165,000 barrels per day from 80,000 as crude output creeps up. That will help Ecopetrol reach target refining capacity by then of 650,000 barrels a day.
"We reached a $104.5 million deal for salary increases," Vecino said of the pay deal which is valid for two years.
The stoppage was the first in the country's oil sector in nine years, though labor disruption has been widespread this year in the country's coal mining sector, with weeks-long stoppages at the two biggest producers of the mineral.
"It was a deal which enabled the project to continue without causing significant delays to the timetable," a source at Reficar said.
Colombia's biggest refinery, Barrancabermeja, is in the central province of Santander and has a refining capacity of 250,000 barrels of oil daily.