Why Safari is consuming so much battery?
Solution 1:
I had this same problem for the first after updating my iPhone 6s to iOS 11. I wasn't using Safari as I use Chrome but it would consume up to 50% of my battery and I was having to charge more frequently then before.
The solution was to disable iCloud syncing for Safari:
Settings → Apple ID → iCloud and turn off Safari.
My phone is now behaving 'normally'.
Solution 2:
That's not total battery used, it's the percentage of battery used out of all battery used for the last 4 days. So you started out with 100% battery on monday and on friday you had 80% left. If safari is listed as 74%, then that means about 15% of the 20% was used by safari.
Solution 3:
12 minutes in 4 days - but keep in mind other apps may pull up a Safari view, and iOS may be counting that depending on the method the apps use to do it.
Twitter and Mail are two likely culprits there.