BTRFS is a special filesystem just like ZFS. The disk physical block has been broke into fragments.
So firstly you should entry RAID utilities load the disks even only one disk as shown below., if not you wont open the btrfs in naexp.
Secondly RAID utilities will rebuild the structure into a virtual device in naexp as shown below.
Finally you can open the virtual device filesystem in Sector extractor as shown below.