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SUBPRO Subsea Production and Processing
Modelling and multivariable control of subsea systems
Traditionally, the big and easily available oil fields
offshore producing from a topside processing
plant have already been developed. The oil and
gas industry now focuses on increased oil and gas
recovery from brownfields and on development of
smaller oil and gas greenfields. Subsea process-
ing will be a key factor both for increasing oil and
gas recovery on existing fields and for making new,
smaller oil and gas fields economically feasible.
Subsea processing plants are small compared to
topside processing plants and have fast dynamics
and strong interaction between units. This fast
dynamics poses challenges with transients and
modelling which are important for analysis and
design of online multivariable control and optimi-
zation. The control oriented models need to be fast
and sufficiently accurate to describe the physical
properties of the subsea processing plant. Thus,
the objective of this subproject is to create stand-
ardised models for a complete subsea processing
plant, analyze and improve interacting control
loops and design a multivariable control structure
to utilize the strong interactions and fast dynamics
Project manager and main
PhD supervisor, Prof. Olav
Egeland
PhD candidate, Torstein
Thode Kristoffersen
Co- supervisor, Associate
Prof. Christian Holden
Co-supervisor,
Prof. Sigurd Skogestad
GLCC
Phase splitter
De-liquidizer
in
Q
1
Q
2
Q
3
Q
5
Q
out
liq
Q
,
out
gas
Q
,
1,
liq
h
5,
liq
h
1
p
to handle transients and optimize production, e.g.
linear/nonlinear Model Predictive Control. An
important research objective will be to find the
minimum buffer volume necessary to sufficiently
control the process and handle transients with
multivariable control.
The models to be developed will start from recent
separation technology, (e.g. the CompactSep
separation system developed by Statoil in collab-
oration with Chevron, Petrobras, Total and FMC)
and extend with boosting and cooling, including
actuator dynamics, processing time delay and
transmission of signals and power. An intension
is that the modelling work should result in a
general framework for standardized modelling of
subsea processing plants. A laboratory of several
microcontrollers is to be constructed and run
with various parts of the complete control model
of compact subsea process to study the effect of
increased time delay subsea. During the modelling
work, focus will be given to numerical solutions of
the models for the simulation to be fast enough.
Figure 15. CompactSep, an example of a separation system to be modelled. Patented separation process by
Statoil. Picture from presentation at the 22nd Mediterranean Conference on Control and Automation 2014.