Ann: Operations Update, page-238

I think some people are getting confused between proppant and fracking fluid, the proppant is the "sand" that holds the cracks open, hopefully you get as little of that back as possible.

The fracking fluid needs to come back to lower the interstitial pressure so oil has some drive to come out from the rock - in very simple terms flow is a result of movement from high to low pressure so the pressure created during fracking needs to be released by retrieving the fluid used to fracture (there is way more to it a molecular level with non Darcy flows etc but this the basics)