Advanced control package mitigates slug flow
leading to increased productivity
Once considered an “unavoidable evil”, slug flow is now tamed with the introduction
of an integrated range of control software and services
ABB is introducing a package of software and services that aim to increase production efficiency by improving slug
management. Production can be improved by between 5 to 15 percent per pipeline, by enabling operation in an unstable
flow regime whilst securing a robust and predictable operation, thereby freeing-up operators to manage other tasks. The
package is a non-intrusive approach to handling fluctuations in oil- and gas production systems that enable substantial
increases in production and improved regularity and predictability, leading to reduced off-spec production and
environmental impact.
At certain mixtures of gas and liquid in a riser system, large bodies of liquid can be formed and will exit the pipelines in
uncontrolled bursts followed by large volumes of gas. These bursting bodies of liquid are called slugs, and the
phenomenon is called slugging. If not handled, the slugs lead to volume bursts that are higher than the acceptable
thresholds of the processing facilities, causing shutdown and loss of production. A common way of reducing slugging is
to close down on production chokes thus restricting production. Handling of variations, or instabilities, in oil- and gas
production systems is of high priority for operators as they can result in unplanned shutdowns, increased maintenance,
off-spec production, metering problems, flaring and reduction of average operating capacity and more.
ABB offers a suite of software and supporting services to tackle the production efficiency challenge, independent of the
control system currently in place.
“We have the competence and know-how in process behaviour and shaping using a structured approach and advanced
control principles; we are good at understanding the process and the control theory behind it and applying that control
theory,” says ABB’s Sverre-Oliver Halvorsrod. “This level of competency is normally found downstream where the
economic climate is traditionally tougher and margins are tighter. But with today’s pressure upstream, the impact here
can be significant with a potential of increasing the production by 1 to 4 percent, reducing energy consumption and
aiding operators to focus on the main task: secure, robust and efficient operation.”
This competency is the basis of the entire slug mitigation solution. The software is represented by the Slug Management
Suite which seamlessly integrates with one another and comprises:
Active Flowline Control stabilizes the pipeline by manipulating the flowline outlet. It is a control solution which actively
manipulates the flow line outlet control valve or choke based on properly chosen measurements in the pipeline and the
downstream processing facilities. It stabilises a production pipeline and prevents large, riser-induced slugs from being
formed. The aim is to allow production to operate at the highest average valve/ choke opening or at the lowest wellhead
platform (or, subsea manifold) backpressure without causing shutdown or overload of the downstream processing
facility. As such it is used to control and stabilise multi-phase flow in gathering systems, risers and flow lines and as such
prevents flow and pressure surges and smoothes the flow without increasing the backpressure.
Active Slug Mitigation - in case of slug variations, or a flow regime which is not possible to stabilize by Active Flowline
Control, Active Slug Mitigation minimizes the impact by reducing flow variations through the processing facilities. This
requires controlling at least one of the inlet separator(s) outlet valves. This means control of the inlet and the outlet of
the separator can be coordinated so as to increase the maximum average pipeline/ choke opening or minimize the
associated backpressures even more than without such integration.
Page 1 of 2 Slug Management Suite
Driving the upstream demand is the fact that ageing assets create slugging which was not present earlier. Active
Flowline Control helps stabilise the system against the slugging effects. “Today we have better ways of handling these
slugging issues. While there are other solutions, some involve actually reducing production in the pipeline until you reach
an area of stability. With the ABB technique, however, not only is it more cost efficient than many of the alternative ways
of slug management, there is no need to reduce production.
“Handling of the slugs is often a trade-off between high production, operational robustness and investment costs,”
explains Halvorsrod. “Uptime is normally prioritized over high production, thus there is a potential production
improvement with the ABB solution. The Slug Management Suite itself is a result of many years of experience along with
the competency of ABB’s service engineers.
“In the Norwegian sector we have examples whereby we have reduced alarm rates by 70 percent and compression
energy by 20 percent. We have increased uptime by five days over a period of six months. It really is quite impressive
what we can achieve.”
ABB is a supplier of power and automation products, systems, solutions and services to the oil, gas and chemicals
industry, with a complete and integrated scope of supply capability that ranges from plant electrification to control,
optimization and safety systems, smart field instrumentation, analyzers and telecommunications systems. ABB is active
in all segments - onshore and offshore upstream, midstream and transportation, refining, petrochemicals and chemicals
– with the aim is to boost the productivity and efficiency of the entire value chain.
http://www.abb.com/oilandgas
http://twitter.com/ABBoilandgas
Note: For the associated image for this release, please see the data file details.
For more information please contact:
Stuart Young
Tel: 01224 592 123
Stuart.young@gb.abb.com
www.abb..com/service
Page 2 of 2 Slug Management Suite
ABB Limited
Hareness Road
Altens Industrial Estate
Aberdeen
AB12 3LE
8/9/15