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19 distribution functions in 3 dimensions – directions in which
particles can propagate with certain probability.
In recent years different models for simulation of
multiphase flow have been proposed. Most popular among
them are Color-gradient model, Shan-Chen model and Free
energy model.
At the start of the simulation pressure gradient of the real
experiment is represented by setting corresponding densities at
inlet and the outlet of the simulated plug. Then in each timestep
streaming and collision steps are applied and densities and
velocities in each lattice are calculated. This continues until a
steady-state flow is reached, i.e. difference in velocities from
one timestep to another is insignificant.
To calculate the permeability of the simulated plug, an
average velocity of all lattices is put into Darcy’s equation with
all of remaining variables known – pressure gradient, viscosity
of fluid. To validate LBM, after first results are obtained, they
are compared to experimental data and by calibrating the
existing model can be verified.
This method of obtaining permeability has been used in
the past and some accurate results have been reached.
Main benefit of LBM is that it is significantly cheaper
than doing the actual experiment for the same purpose. On top
of that, computational time of LBM is also a huge advantage.
In conclusion, usage of LBM in the oil & gas industry is
cost and time effective relative to standard methods of
acquiring absolute and relative permeability and it can be used
for unlimited number of times for different rocks by just
changing the inputs.
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COMPARISON OF DUAL GRADING DRILLING
TECHNOLOGY TO SINGLE GRADING DRILLING
TECHNOLOGY IN DEEP WATER ENVIRONMENT.
Student:
Scientific adviser:
Vazeri Samandar
as.prof. S.A.Rzazadeh
IV course, group 230.4
As technology progresses the definition of Deepwater
becomes greater and greater every day, and as the water depth
increases, the associated technical, economic and safety
complexities
increase
proportionately.
Therefore,
for
improving wellbore integrity, reduce overhead costs and, most
importantly, provide a safe working environment. Applying a
dual gradient technology to offshore drilling is not a new
concept, but one that is being addressed with new fervor and
can help meet these industry goals.
Before analyzing the technical and safety aspect of dual
grading drilling technology first take a look what is single
grading drilling technology. In conventional method we are
drilling with single mud gradient due at the water depth (3000-
7500 ft)
convention technology becomes unreliable. Because
margin between the pore and fracture pressures in deep waters
become narrower that tend to create problem like early kick,
lost circulation and formation damage. Additionally, single
grading drilling technology is not cost effective as compare to
dual grading drilling technology. Therefore, for minimizing all
these issue and cost constrains we need an advance
methodology as dual gradient drilling method.
The dual gradient drilling technique involves the use of
two different pressure gradients in maintaining the bottom hole
pressure. The same bottom hole pressure in the conventional
method can be achieved using the dual gradient method.
Several methods have been proposed to achieve dual gradient
130
in the industry today. In one of the methods the marine riser is
filled with a low-density fluid (sea water, 8.66 ppg), this helps
in reducing the pressure in the exposed sediments of the
wellbore while heavy density fluid runs from the sea floor to
the bottom hole.
The major challenge in deep-water drilling is the narrow
margin between the pore pressure gradient and the fracture
pressure gradient. Therefore, dual grading drilling in the only
reliable technology for solving this issue because when we are
using combination of two different mud column margin
between the pore pressure and fracture pressure increase. This
alone makes the dual gradient drilling method very attractive.
Furthermore, One primary benefit of the wider margin
between the pore and fracture pressures in dual gradient
drilling is the elimination of several casing strings. A
comparison between casing selection in dual gradient drilling
and conventional drilling lesser number of casing strings
allows for deeper target depths, greater final hole size, and
setting larger production tubing strings. It is also important to
note that well kicks and lost circulation would be minimal
because of the wide margin between these pressure gradients.
Other benefits of dual gradient drilling include cost and time
savings; which allows drilling in any water depth and has lower
weight and space requirements on the drilling rig.
In conclusion, dual grading drilling technology is far
more cost effective and reliable then single grading technology
because of its unique method for improving well construction
and safety of drilling operation.
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