While fracking has become more popular in the last few years, the big reason for low oil prices at the moment is the Saudis. They saw $billions in investments in the various drilling, etc efforts and decided to flood the market to kill their competition and sacrifice profits now to keep their dominance in the long run.
From a purely economic perspective, it's a good move on their part.
Actually, it's mostly related to a falloff in demand:
"After mid-2014, the lion’s share of the decline in oil prices has been caused by negative oil-specific demand shocks and, to a lesser extent, by negative aggregate demand shocks. In contrast, the role of the oil supply (understood as the current physical availability of crude oil) has been small."
From a purely economic perspective, it's a good move on their part.