(Corrects natgas production figure in paragraph 3 to 1.215 billion cubic meters rather than 1.215 million)

HAVANA, Dec 26 (Reuters) - Cuban oil and gas output rose only slightly to the equivalent of 4 million tonnes this year despite a significant increase in investment, state-run media reported on Wednesday.

Oil output was 2.9 million tonnes, or around 57,000 bpd, assuming 7 barrels per tonne, down slightly from the 2.98 million tonnes reported in 2006.

Natural gas production was reported at 1.215 billion cubic meters, up from the 920 million cubic meters reported in 2006.

Vice President Carlos Lage, during a Christmas Day tour of oil facilities, praised efforts to maintain output despite the natural depletion of existing wells, and in particular the use of natural gas to generate 15 percent of the country's electricity.

Cuba has prioritized energy production and savings in the face of skyrocketing prices and despite its alliance with oil-rich Venezuela.

Lage said Cuba produced 47 percent of its fuel needs.

Cuba imports the rest of its fuel from Venezuela in exchange for the services of 31,000 medical personnel and 8,000 other Cubans working in the South American country.

Cuba bought and rented 10 Chinese drilling rigs in recent years, Lage said, and drilled 32 wells in 2007 -- mostly in partnership with Canadian company Sherritt International (S.TO: Quote, Profile, Research) -- compared with 23 wells in 2006.