Best layman's explanation of hydraulic fracturing. Posted 29 Jun. 2015 on oilpro.com that shutdown 2 Aug. 2017.I kept it as a private link but release it now as it has useful info.

1. Where does all the
water used in hydraulic
fracturing go?
FROM OILPRO DISCUSSION POSTED 2015/06/29
OILPRO SHUT DOWN 2017/08/02, PUBLIC REPOST

2. Preamble added later – setting the scene

4. The simplest answer to [the] question
The water either stays in the fractured rock (reservoir),
or it comes back to the surface
commingled with the hydrocarbon as it’s produced.

5. The question posed is one of the best
questions
Fear mongers may serve a purpose by elevating awareness via dramatization.
What those same fear mongers should never be allowed to do is directly influence public policy
and statute through emotion and ignorance.
[In the UK it’s been suggested that the National Physics Lab or the Department of Energy &
Climate Change be a neutral arbiter between the Government, the Industry and the Public.]

6. Where do [water or water-based fluids]
go during the fracturing treatment?
In general they travel from a tank / pit,
through blender,
through a high pressure pump,
down treating iron at the surface,
through the wellhead,
down some sort of tubular steel (tubing / casing) in the well itself,
and through either perforations or slots or openings in those tubulars,
into the rocks that have been holding the hydrocarbons in place for millions of years.

7. What happens normally
If
the pressure at the surface
+ the weight of the vertical column of fluid in the wellbore
– the friction pressure
> the failure pressure of the hydrocarbon bearing rock,
it is inferred that the rock will first fail along some plane of relative weakness.

8. Industry assumption
Most hydraulic fracturing models used by the oil and gas industry
simplistically assume that the ensuring failure is a “crack”
that we call a hydraulic fracture
and that the crack is vertical in nature.

9. What happens normally 2
As the volume of the fracturing fluid (i.e.; water)
that is pumped at the surface increases
the crack (i.e.: hydraulic fracture) volume also increases in size.

10. Very important term in hydraulic fracturing
“Fluid efficiency” is simply
the volume of the hydraulic fracture created
divided by the volume of fluid pumped.
Therefore, fluid efficiency will never be (for practical purposes) greater than one.
If fluid efficiency is 50%,
the inference is that a hydraulic fracture was created
that has a volume equal to 50% of the volume of fluid pumped.

11. Where did the other 50% of the fluid go?
In most instances the hydraulic fracturing fluid (water) leaked off into the hydrocarbon bearing
formation during the injection period.
There are circumstances where the hydraulic fracture migrates outside of the hydrocarbon
bearing zone.
Obviously the fluid creating the fracture is intrinsically linked to the crack (hydraulic fracture)
Itself.

12. Industry assumption 2
To keep things simple for this conversation
it’s fair to assume that for most instances
the hydraulic fracture is generally kept
contained within a few tens of feet to a few hundreds of feet
from the hydrocarbon bearing zone itself.

13. Once the well is put on production
The fluid (water) that created the fracture is bound in the subsurface due to three physical forces
a) capillary bound in the rock after it leaked out of the crack
b) trapped by portions of the fracture were not adequately propped open
c) it simply stays resident in the reservoir due to the most prevalent force in the reservoir –
gravity.

14. But
The portion of the fluid that is not trapped in the reservoir
will most likely be produced along with the hydrocarbons over time.
[Meaning, it won’t be found in the water table as often stated.]

15. The potential for tubulars to leak causing fluid
to thief off into adjacent or shallower zones?
Of course it could happen.
If you can conceive of something happening in nature, there is a high probability that it “could”
happen.
Does it happen with any alarming frequency?
No.

16. The fundamental reasons are quite
simple
Wellbores are engineered and installed (casing and cement) in such a manner to prevent that
“leaking” from happening.
Why is so much time and attention paid to this engineering and wellbore construction phase?
Because the operator drilling and operating the well makes more money by doing it right the first
time!
There is absolutely no motivation in the industry for creating a faulty or leaky wellbore.

17. No short term cost advantage from cutting corners
The average lifespan of a producing well in North America is greater than 10 years.
No reasonably intelligent oil and gas operator would ever want a wellbore to leak fluids over the
producing life of the well.
The fluids that are injected create value and the fluids that are produced are fungible and create
value.
The simplest investor in the world never compromises a value stream.

18. To have greater definition and insight
into hydraulic fracturing
[People] must at a minimum come at it like you did.
Ask questions. Your question was intelligently framed.
The answer, like all facets of life, has many complexities and angles.
Don’t be afraid to ask. Ask the same question to many people.

19. Likely get many variations on the same theme
Listen to all the answers,
and make sure you let your brain lead you down the path of what makes the most sense.
Physics isn’t the land of fear.
Physics is a science with reasonably clear, easy to understand concise explanations
to how forces in our world interact

20. In closing
Don’t be intimidated by people who studied physics,
any more than you are influenced by people who studied acting.
Ask questions.
Your question may show people you are more concerned for the answer
than the people who believe they have all the answers.