The Zeta
Model software is one of the two primary components that
comprise the Zeta
Safety System for
well intervention operations. The Zeta safety system
utilizes data and modeling to
eliminate the guesswork commonly
associated with well intervention design and operations.
The system was designed
to avoid
catastrophic buckling and bending failures of well
intervention stacks. These failures are costly, and could
involve
human injury and unplanned release of wellbore pressure
to the atmosphere.
The Zeta
model is
based on a non-linear finite-element (FEA) approach,
purpose-written for analyzing intervention structures.
The FEA analysis is run repeatedly at very small
time increments to perform a dynamic analysis.
A finite difference, forward difference scheme
is used to determine the acceleration of each
component in the stack, and the associated dynamic
forces. The model accurately calculates the buckling
instability of the stack. It also calculates
the Von Mises stress throughout the structure,
and compares the guy wire loads to user defined
limits. Thus it examines the structure for both
modes of failure; failure due to buckling instability
and failure due to yielding of a component in
the structure.
Validation
of the Zeta Model
Extensive work has
been performed to validate the results of the Zeta
model. The model predictions
vs. analytical results were excellent. A white
paper is available
for review.
Buckling load model comparison were within 1%
of each other under the same conditions (zero gravity
situations - as typically stipulated in the analytical
solution).
Critical frequency model comparisons
were within 2% of each other under the same conditions.
For additional
information, the following are available for download:
