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Click here to download the Meyer 2008
User’s Guide, including more information about Multilayer
Fracturing
Multilayer or limited entry fracturing is a process whereby multiple
zones are stimulated simultaneously. The initiation and propagation of
multilayer fractures is governed by conservation of mass and momentum for
the system of fractures. This process is controlled by the limited entry
techniques employed which include the number of perforations, perforation
spacing, near wellbore effects, fracture pressures, stresses, etc.
The methodology for limited entry fracturing was first presented by
Elbel et al. where an analytical PKN fracture model was linked to an
analytical wellbore model. Elbel developed his formulation based on an
analogy of Kirchoff’s current and voltage laws to those of mass and
momentum conservation.
Although the solution techniques presented here are similar for solving
a non-linear system of equations, the implementation is not limited by the
fracture model, wellbore restrictions or time dependent dissipation losses.
Our formulation is based on conservation of mass and momentum (formulation
based on “Transport Phenomena”).
The methodology presented here for multilayer fracturing couples a
general hydraulic fracturing simulator with a general wellbore model. The
fractures may coalesce, interact or may remain isolated from one another.
The governing equations presented are not specific to any limiting
constraints. Only the constitutive relationships and boundary conditions
imposed on the fracture geometry model govern the interaction behavior of
the fracture system.
MFrac allows the simulation of multilayer or limited entry designs. Note
that this is not the same as multiple parallel fractures in a zone, which
is also available. Different perforated zones may be entered. For each
zone, the number of perforations, perforation diameter, and number of far
field fractures may be entered. MFrac does a true limited entry solution in
that it considers that the rate going into each fracture is a function of
time (not a constant). In fact, cross-flow between fractures is supported.
Note that when the total rate goes to zero, there is cross flow from
fracture number one to fracture number three.
When running a multilayer case, all of the MFrac plots contain data for
all of the different layers.
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