Indonesia will open more oil and gas exploration areas in the Natuna Sea following a tentative agreement with Vietnam last week on sea boundaries, a mines and energy ministry spokesman said on Monday. Vietnam and Indonesia have been in lengthy talks to settle their sea boundaries in an area believed to be rich in hydrocarbons. "The government will open more exploration areas there. The areas are very promising for oil and gas exploration as potential reserves of oil and gas are big," spokesman Nurwinakun said. Nurwinakun expects that the areas would be opened later this year.