If you can do one mile in 6:30 without injury or great pain at least once a week
If you continue at the same speed but increase the distance and time by 10 percent per week and if the pain does not increase
Then you would be able to do 2 miles in 13 minutes in about 7 or 8 weeks
1.1^7<2<1.1^8
Some personel trainer organization suggests not to increase training "volume" by more than 10 percent per week