Does this include that which is extractable only via horizontal-drilling/fracking?
That is proved reserves, meaning the field has been located and flow tested, regardless of the drilling, completion or production method. Also, they have to be economic to produce in recent pricing structures.
It does not include fields drilled but not flow tested, located on seismic data only, fields expected due to geology. It does not include fields such as this that contain oil, but are deemed to expensive to produce, regardless if that is production cost, regulation or tax costs.
Total proved reserves of oil are generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and geological conditions.
more at the link
I should have also clarified, that only includes the oil in the field that meets the criteria above.
If a field contains 100 million barrels of oil, but it is only economic to get the first 5%, only 5 million barrels is counted as proved reserves. The proved reserve number could double or be cut in half just by change in the price of oil. The 1.7 trillion number was from measurement and data back in 2014.