Can't delete a logical volume group created from a blank disk image

Hi all,

I'm a recent convert from Windows, so do bear with me while I grapple with all the new terminology.

Basically, here's the problem: I've been trying to create an encrypted drive and have been at it for a few hours now. I ended up with two 'logical volume groups' created from blank disk images, neither of which are password-protected, and one of which I quite stupidly named "hidden folder" and can't rename now. Anyways, I decided to throw it all away and start right from scratch, but now disk utility won't let me delete these two logical volume groups despite me dismounting both devices, trying to trash the containing folder, etc. Some searching about online has gotten me into the belief that there should be an 'erase' tab in the disk utility window which is not showing up when I click on those drives (however, the erase tab does appear when I click on the indented partitions on each drive). Here's a screenshot to give you guys an idea:

-Here's the disk utility window. The two drives I'm trying to get rid of are "Hidden Folder" and "HD2"

-Here's what I suppose would be called the 'containing folder' in which both drives reside

-And finally my setup, just in case it's relevant

Oh and btw this would be my first post here! How exciting 😀

Thanks in advance,

Arthur