Here is the full list of all 31 The Oil Blue: Steam Legacy Edition achievements.
Booted up the Oil Blue Achievement App
Reclaimed your first island
Reclaimed a second island
Completed the tutorial
Achieved Rank 48
Achieved Rank 45
Achieved Rank 42
Achieved Rank 40
Achieved Rank 36
Achieved Rank 32
Achieved Rank 28
Reclaimed a third island
Reclaimed a fourth island
Reclaimed a fifth island
Reclaimed a sixth island
Reclaimed a seventh island
Reclaimed an eighth island
Reclaimed a ninth island
Reclaimed a tenth island
Reclaimed an eleventh island
Reclaimed a twelfth island
Achieved Rank 25
Achieved Rank 22
Achieved Rank 18
Achieved Rank 15
Achieved Rank 12
Achieved Rank 10
Achieved Rank 9
Achieved Rank 8
Achieved Rank 7
Achieved Rank 5