What I really like here is the composition. You have given a good feeling of calmness and tranquility. This is also helped with the very nice colours.
What is also to be admired here is the use of the texture and the shapes of the mountains and clouds. The fact that you have kept the details on the mountains and they are not just a silhouete is also something that I like.
Of course this is all helped by the fact that you used long exposure as the title says , 20''
Why don't you try adding a frame to the image? I believe it would be even better.
All in all I think that this photo is something you should be proud of Good work