Summary
This is the second of two papers describing control experiments on a
medium-scale slug rig. The first paper (Sivertsen et al. 2009) describes
experiments performed on a small-scale laboratory rig built at the Norwegian
University of Science and Technology (NTNU) Department of Chemical Engineering.
These experiments showed that, despite noisy measurements, it is possible, with
feedback control, to "stabilize the flow" (i.e., to achieve reasonably smooth
flow in the normally riser-induced severe slug-flow region) using only topside
measurements. The question to be answered is whether these results also apply
for larger riser systems.
In the present paper, we look at some results obtained from a 10-m-high,
3-in.-diameter medium-scale test rig located at the Statoil Research Centre in
Porsgrunn, Norway. Several cascade control structures are tested and compared,
both with each other and with the results obtained from the small-scale NTNU
loop. The rig was also modeled and analyzed using a simple three-state dynamic
model.
The new experiments were successful and confirm the results of Sivertsen et
al. (2009) from the small-scale rig. The valve opening with nonslug flow
operation could be increased from approximately 12% with no control to almost
24% with control using topside measurements only. This makes it possible to
produce with a larger production rate and increase the total recovery from the
producing oil field. The valve opening with control could be further increased
to approximately 28% using measurements from the bottom of the riser, but such
measurements may not be available in many cases.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
24 July 2008
- Revised manuscript received:
11 May 2009
- Manuscript approved:
23 May 2009
- Published online:
14 January 2010
- Version of record:
14 January 2010
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