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Click here to download the Meyer 2008
User’s Guide, including more information about Minifrac
methodology
Minifrac analysis provides a method of estimating fracture efficiency,
closure pressure, fracture dimensions and leakoff coefficients prior to
designing a full-scale fracture treatment. These types of analyses, as
originally formulated by Nolte, quantify the fracturing process as
estimated from the measured pressure decline data.
Most minifrac analyses are based on Nolte’s equations and do not account
for the effects of fluid rheology or the conservation of momentum. The
measured pressure decline data is simply used in place of solving the
momentum equation. Neglecting momentum can result in unrealistic
estimations of fracture characteristics and fluid leakoff coefficients that
are critical to the design of the main fracture treatment.
Up until 1987, only the width-opening pressure relationship and
pressure decline data were used to estimate minifrac characteristics. Lee
improved upon this by including Biot’s energy balance equation for
two-dimensional type fractures geometry models.
The energy balance method does eliminate some of the anomalies in
minifrac analysis. However, this method does not fully account for viscous
driven fractures.
Meyer and Hagel reported a new minifrac methodology. The methodology
solves the conservation of mass and momentum equations for power-law type
fluids using the 2-D fracture propagation equations-of-state. The solution
technique does not assume that the fracture width is proportional to the
measured pressure. Instead, the governing mass and momentum equations are
coupled with the measured closure time to predict fracture propagation
characteristics. From the numerically simulated fracture geometries,
pressures, fluid efficiencies and leakoff coefficients, you can determine
which fracture model most closely corresponds to the measured pressure
response and formation permeability.
The main advantage of this technique is that it satisfies both
conservation of mass and conservation of momentum. Additionally, the
technique correctly accounts for flowback, interference closure, time
dependent leakoff and fluid rheology.
The numerical results are used in conjunction with the measured pressure
decline data to history match a number of fracture characteristics such as
fracture height, pay zone height, Young’s modulus and spurt loss. Closure
time can also be more accurately estimated from these parametric
studies.
The equations of mass conservation, continuity, width-opening pressure,
momentum and constitutive relationships for fracture propagation models are
formulated based on the methodology of Meyer and Hagel.
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