Select solid elements within enclosed volume?

Hi,

Is there a way of selecting elements within a volume (enclosed surface)?

So in my case, I have this solid hex mesh made with shrinkwrap: 

<?xml version="1.0" encoding="UTF-8"?>

I now want to group the elements in separate components. For example, I want to select the elements within this tube and group them separately:

<?xml version="1.0" encoding="UTF-8"?>

I have hundreds of these enclosed surfaces that I would like to associate with elements. Doing this manually is, as you can imagine, very mundane work.

Do you have any appropriate method for this type of entity selection?