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OH – ST - ET: Analysis of Dynamic Data in Shale Gas Reservoirs – Part 2
p 5/18
Using this model let us make a 10-year forecast based on the last flowing well pressure FBHP
of 1770 psia. Given the extremely low permeability, the drained area is very close to the
fracture itself. Closing off the reservoir would not make any difference.
Forecast using the square root extrapolation
2.2 - Material Balance
In a gas reservoir it could make sense to look at a p/Z plot to assess the reserves. This cannot
be done here, because the classical p/Z plot and other related material balance methods are
based on the assumption that a pseudo-steady state flow regime is established, which is quite
clearly not the case here: there is no indication of late time unit slope on the loglog and
Blasingame diagnostic plots.
This is to be expected for many shale gas plays, as the extremely low permeability gives such
a low mobility to the system that transient flow can last as long as many years. Thus,
performing a flowing material balance analysis would be meaningless here.
3 - Advanced analytical model: multiple fractures horizontal well (MFHW)
In Part 1, we have described KAPPA’s analytical multiple fractures horizontal well model. This
model has the advantage over the equivalent single fracture model to account for the real
geometry of the system. The main difference is that it takes into account the interferences
between the different fractures.
2000
4000
6000
8000
10000
12000
14000
16000
18000
Gas rate [Mscf/D]
5E+8
1.5E+9
2.5E+9
3.5E+9
4.5E+9
5.5E+9
6.5E+9
Gas volume [scf]
qg
Qg
qg model
Qg model
2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
3000
7000
Pressure [psia]
Pi
p
Forecast
Production history plot (Gas rate [Mscf/D], Pressure [psia] vs Time [hr])