I suppose the sand mixes with the oil for extraction and separation? Is it recoverable for reuse? Or does it stay in the fracked cavities?
The sand is mixed with gel’ed (thickened water) on the surface and pumped down into the horizontal length, which is lined with perforated pipe. Then the pressure is raised enormously and stage by stage, the rock is fractured. The rounded sand embeds itself in the fractures so that when the pressure is removed, the 2 miles of rock pressing down doesn’t reclose the fractures.
Oil then can flow. About 1000 barrels per day on day 1, down to 600 by the end of month 1 and maybe 400 bpd end of year 1. The gel’ed water also comes back up, as does very salty natural water that is in the rock down there. It comes up with the very thin oil that is in shale. Both are collected in onsite tanks and hauled by truck. The water goes to a disposal well that it is pumped down into. The oil goes to the train railhead.
In the Bakken, because of the salt, more water is frequently hauled to the well site and pumped down into the well, to dissolve salt encrustation. That water comes back up and has to be hauled to the disposal well.
It’s all VERY expensive. Wells cost $10 million to drill and frack, and then mineral royalties take 16ish% of the revenue, and North Dakota taxes another 5%. The $10 million is borrowed money at about 6% with 5 year repayment reqmt(often).
The train transport means about $15/barrel is deducted from the refinery price they are willing to pay. What’s left is south of $60/barrel and with all those costs, the industry will fail. If oil gets much cheaper, probably by the end of this winter.
Only a govt subsidy could save it.
The intent is for the sand to get stuck in the fissures of the shale and keep it propped open so that the oil can flow. If the rock is fractured and then collapses on itself, there are no gaps for the oil (or gas) to flow through. The frack sand is needed not only for the shales of Bakken in North Dakota and the Eagle Ford of south Texas, but also the Permian in west Texas and the Marcellus gas wells in Pennsylvania.