Morning gents,
I mentioned that I would get back to you after the GPS and had an opportunity to talk to the frack guys and some engineers that I know. It pretty much came down to this.
In terms of fracking fluids, the only common elements are sand and water (sometimes oil if there are clays present). Depending on the specific characteristics of the formation, the frack may use a variety of surfactants (akin to detergent), small amounts of acid (to clean-out the inflow areas) or a raft of other chemicals to facilitate the flow of the oil/gas. That said, by in large, these chemicals are refined derivatives of oil like naphtha, toluene, etc.
Relative to direction that a frack might travel, that is dependent on the presence of the natural fault lines that are already in place in the formation. Other than the initial point of introduction from the casing, the materials will travel a route that follows the natural 'fractures' in the formation. These natural lines can go any direction, however, because the oil is a byproduct of organic deposits and those deposits are laid in a horizontal-style fashion, and the frack will (at least initially) travel in a spider-web configuration (as was suggested).
The distance of the frack is entirely a function of the amount of materials that is injected and the pressures that are used. Combine this with the number of perforation sites employed in the casing and that distance is affected directly.
Lastly, in order for a pool of oil to exist, geologically speaking, there must be a cap rock and base rock to contain that pool. The cap and base act top contain the oil and prevent it from easily migrating into higher zones. The cap and base are highly unlikely to be affected by the actual frack.
