Oil composition changes due to fracking? Which components are most affected and where does the difference end up in the material balance?
Well, not due to fracking....more like due to the types of rock structures that fracking taps. Fracking opens up paths in what are called "tight" rock formations (i.e. the pores in the rock are small). The heavier oil molecules move through the tight/small pores much more slowly than the lighter fractions. Pre-fracking methods could only tap "looser" types of rock formations (like sandstone), through which the heavy fraction moved about as easily as the "lights".
Soooo......what comes out of the well is "enriched" with lighter fractions, mostly C1-C5 with lesser amounts of larger molecules. Heavier stuff stays in the rock.
Less heavy stuff, less refining needed.