National Academy of Sciences of the
United States of America
Gas production in the Barnett Shale obeys a simple
Ten years ago, US natural gas cost 50% more than that from Russia.
Now, it is threefold less. US gas prices plummeted because
of the shale gas revolution.
However, a key question remains:
At what rate will the new hydrofractured horizontal wells in shales continue to produce gas?
We analyze the simplest model of gas production consistent
with basic physics of the extraction process.
Its exact solution produces a nearly universal scaling law
for gas wells in each shale play, where production first declines as
1 over the square root of time and then exponentially.
The result is a surprisingly accurate description of gas
extraction from thousands of wells in the United States’ oldest
shale play, the Barnett Shale.
Natural gas from tight shale formations will provide the United
States with a major source of energy over the next several decades.
Estimates of gas production from these formations have
mainly relied on formulas designed for wells with a different
We consider the simplest model of gas production consistent
with the basic physics and geometry of the extraction process.
In principle, solutions of the model depend upon many
parameters, but in practice and within a given gas field, all but
two can be fixed at typical values, leading to a nonlinear diffusion
problem we solve exactly with a scaling curve.
The scaling curve production rate declines as 1 over the
square root of time early on, and it later declines exponentially.
This simple model provides a surprisingly accurate
description of gas extraction from 8,294 wells in the United States’
oldest shale play, the Barnett Shale. There is good agreement with
the scaling theory for 2,057 horizontal wells in which production
started to decline exponentially in less than 10 y.
The remaining 6,237 horizontal wells in our analysis are too
young for us to predict when exponential decline will set in, but
the model can nevertheless be used to establish lower and upper
bounds on well lifetime.
Finally, we obtain upper and lower bounds on the gas that
will be produced by the wells in our sample, individually and in
The estimated ultimate recovery from our sample of 8,294
wells is between 10 and 20 trillion standard cubic feet.
Tad W. Patzeka,1,
Frank Maleb, and
Edited by Michael Celia, Princeton University, Princeton, NJ, and
accepted by the Editorial Board October 2, 2013 (received for review
July 17, 2013)
Proceedings of the National Academy of Sciences