Colombia's oil reserves had risen 2.9 percent to 2.445 billion barrels by the end of 2013, up from 2.38 billion barrels a year earlier, taking reserves to their highest despite a missed exploration target, the energy ministry said on Monday.
Foreign investment into the Andean nation's oil and gas sector has surged in recent years and the government is preparing to tap non-conventional or shale resources offering such blocks in its 2014 oil auction which concludes in July.
Though security has improved massively in the last 10 years due to increased military pressure on the leftist FARC and ELN guerrilla groups, the rebels have intensified bomb attacks on oil pipelines, with 259 attacks in 2013 alone, the oil industry association said.
"2013 was a difficult year for the sector because it had to contend with attacks and social conflict which impacted on oil sector activity," said Energy Minister Amylkar Acosta, adding that reserves were now at their highest ever.
He said some 115 exploration wells had been drilled in 2013, below the target of 135.
Santiago Angel, Vice-President for Hydrocarbons at the national association for industrial development, ANDI, welcomed the growth in reserves but said they were still uncomfortably low, still equivalent to around seven years output.
"It's good news if you look at it in percentage terms but overall it's still worrying," he said, suggesting upwards of 15 years production in reserves as a desireable level.
Gas reserves by Dec. 31, 2013 stood at 6,409 tera-cubic feet, the ministry said.
Colombia produced just over 1 million barrels per day of crude in 2013, up 6.6 percent from 944,000 barrels per day in 2012. Gas production last year was 1.174 billion cubic feet per day on average, up 1.6 percent from 2012.
State-run Ecopetrol produces the bulk of Colombia's crude oil and Toronto-listed Pacific Rubiales is the biggest private oil producer.
(Reporting by Luis Jaime Acosta; Writing by Peter Murphy; Editing by Steve Orlofsky, Bernard Orr and Marguerita Choy)