Welcome to... "Micro-Lesson 265"
This riff is an excellent study in the performance of the octave interval on guitar. If you're unfamiliar with them, octaves are a large interval from within a scale that is eight tones away from the scales tonic, (i.e., Tonic /naming note: "G," to Octave: "G").
In the key of "G Minor" the octave is the next "G" tone located eight tones higher from the starting tone, (Tonic: "G"). The interesting thing with this riff is how it applies octaves from off of each note used within the riff. This sound is very unique, and is somewhat rarely applied within most styles.
Some reasons for this being the case are that these octaves can be quite difficult to perform fast - as a riff. Another thing is how the sound created with them is very unique, and may not work well in every melodic /song situation.
If this technique is new to you, take your time getting used to the wide distance between each octave. You can perform this reach either with a pick using, "String Skipping," or you could use, "Hybrid Picking," or it could even be done with, "Finger-style," plucking technique.
However you choose to play this riff, be sure to memorize all of the patterns prior to trying to build up the riffs tempo. When the ideas are committed to memory, turn on a metronome and build up the playing speed. Enjoy!
Micro Lesson 265: "G Minor" Octave Interval Riff