Basic HTML Version
KAPPA Consortium on Unconventional Resources – Draft – 7
th
Feb 2011
p4/10
C - What KAPPA has done so far
In Ecrin v4.12 KAPPA released or updated two specialized plots (square root and material
balance), a set of analytical models and a numerical model that are aimed at addressing all or
some of the following behaviors:
‘early’ time global linear flow orthogonal to the fractures
interference between the different fractures
diffusion of real gas in a tight formation accounting for the increase of the gas
compressibility when the pressure is depleted close to the fractures
pseudo-steady state in the SRV, whenever it occurs
desorption of the gas from the shale
pressure dependence of the permeability
A simple matrix illustrates which model/option can handle what. The white circles correspond
to behaviors that are partially, but not rigorously, taken into account using pseudopressures or
other correcting functions aimed at partially linearizing the diffusion equation.
Square Root
Material Balance
Analytical
Numerical
Early time linear flow
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Fracture interference
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Real gas diffusion
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PSS in SRV
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Desorption
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Stress dependence
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It is no surprise that the Numerical model is the only option that has the capacity to rigorously
address the whole spectrum. But how rigorous do we need to be? The different potential errors
in the other methods are described in Part 1 and quantified in Part 2 of our WEB document.
Both specialized plots and analytical models have their roles and there are many different
parameters in the ‘final’ numerical model. The proposed workflow is to increase progressively
the complexity of the analysis. This starts with straight lines (linear flow) and is refined with
analytical models accounting for flow geometry and fracture interference. Finally it uses the
numerical model to account for everything we know.
Typical workflow (left) and typical history match (right)
Today we believe the methodology and models available in our software are the best (or the
least bad) available to tackle this problem.