eli5 Why is Fracking fluid returned to the hole after extracting the resources?
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Short answer – it’s not.
When you frac a formation you use a gel like liquid to suspend what is known as proppant in the liquid. This gets pumped down into the formation under high pressure which is slowly increased until a fracture happens. This means that the solid rock is fractured and when that happens, the liquid is continually pumped down into the well to increase the size and reach of the fracture.
This fracture cannot go on indefinitely and eventually the pressures rise so much that you realize you’ve reached the limit of the fracture. When that occurs a “breaking agent” is pumped down into the well and this “breaks” the gel like liquid into a much less viscous liquid more like water and that liquid is then pumped out of the well. After breaking the proppant stays in the fracture and holds it open thereby getting the name proppant because it “props” open the fracture.
Sometimes when a frack is broken the pressure from the well causes it to flow on it’s own but many times a pump needs to be placed into the hole.
When turned on the pump will continue to pull the liquid from the hole and eventually oil will flow, if the frack job is successful and they’ve connected multiple oil reservoirs so that it can flow into the 1 well bore.
However you never then pump the frac fluid back down into the hole because it’s now producing so that wouldn’t make sense at all.
Frac fluid may need to be disposed of and in that case it may be pumped down a disposal well but that’s not usually the same hole you just fracked.
Keep in mind it may take many months from when you frac a well until it starts producing oil again.
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