macOS High Sierra not reinstalling— locked OS x Base System
You should see 2 separate entries in Disk Utility one for the internal drive and one for the Recovery Partition, so it looks like your Disk Utility is a little bit confused. In the Disk Utility window try clicking on View button and select the Show All Devices options, this should show you the actual disk and any volumes that are on it. Even though your screenshot from Disk Utility just shows OS X Base System, it does shows the drive as the internal one and the size as 500GB, as if it was the Recovery Partition it would only be about 2GB partition in size. What do you see when you show All Devices?