Genesis Slug Suppression Controller

Genesis
Slug Suppression Controller
g-SSC
Increases Production
Stabilises Operation
Eliminates Severe Slugging
Non-intrusive System
Riser Base Gas Lift Eliminated
Genesis Oil and Gas Consultants, 3 Queens Gate, Aberdeen, AB15 5YL
Tel: +44 (0)1224 201201, Fax: +44 (0)1224 201222

g-SSC : Overview
The g-SSC is an advanced, multi-variable control system aimed at
actively controlling and managing severe riser based slugging (SRBS),
terrain induced slugging and hydrodynamic slugging. The control
system is non-intrusive and has been developed such that it can be
uniquely configured to suit each application using existing
instrumentation and innovative slug recognition software.
The g-SSC is a standalone, PC based control system that works by
identifying and predicting the slugging cycle with subsequent use of
advanced control logic to manipulate a fast acting control valve.
The ultimate aim of the g-SSC is to provide a cost effective slug
suppression system that will improve production, stability and operation
for both greenfield and brownfield systems that exhibit slugging
characteristics.
Pressure (bar a)
Genesis Slug Suppression Controller
30
28
26
24
22
20
18
16
14
12
10
g-ssc OFF
Topside Choke at 100%
g-SSC : The Benefits
The benefits achievable using the g-SSC are system specific. The g-
SSC can be designed and setup to achieve a particular objective; for
example, if the primary objective is oil production then the control
system will be set up to maximise this parameter. Alternatively the
primary objective may be topsides stability in which case the primary
objective would be to stabilise all of the flows from the production
separator. The following gives a summary of expected benefits.
Increased Production
Reduced wellhead back pressure
Reduced startup time
Increased topsides stability, hence reduced maintenance and
increased operating margins
Lower CAPEX when compared to alternative systems such as a
slug catcher
Mitigation of slugging risk for new installations
Increased Production / Reduced Wellhead Pressure
Conditions at Wellhead
g-ssc OFF
Topside Choke
at 40%
g-ssc ON
Topside Choke
variable
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36
Time (hrs)
Pressure at well head Oil Production
Genesis Oil and Gas Consultants Limited, 3 Queens Gate, Aberdeen, AB15 5YL
400
350
300
250
200
150
100
50
0
Production Rate (m3/hr)

Genesis Slug Suppression Controller
g-SSC : Control System
The g-SSC control system is designed to operate seamlessly with the existing distributed control system (DCS). Communication to and from the DCS is
carried out using the OLE for Process Control (OPC) standard.
The g-SSC control system is designed to optimise a separation system
that is operating, or will operate with inherent instability induced by
flowline slugging. The primary objective is to prevent severe or terrain
induced slugging from occurring, however, in addition to the primary
inputs and outputs, the g-SSC also has a number of secondary
functions. In all of the operating modes the g-SSC is linked to the
standard separator level and pressure PID controllers. This provides
a number of advantages over a standard control system.
Advanced anti-trip logic that will prevent the separator tripping if
the slug suppression system loses control.
Ability to control, based on an objective function - separator oil
flow stability.
Improved startup control and reduced startup time through
maximum use of separator volume.
Ability to link controllers and separators to provide overall control
over separators in parallel.
As mentioned above, the control system has a number of different operating modes (ssA modes), two of which are shown below.
MODE ssA20
RISER
PT
PT
g-SSC
TESPAR
Operating mode ssA20 is designed to operate using primary inputs
from two gamma densitometers via slug recognition software called
R
TESPAR. Operation in this mode is only achievable through our close
collaborations with Domain Dynamics and Tracerco.
R
The TESPAR software, designed and supplied by Domain Dynamics,
takes data from two gamma densitometers in series and applies
advanced mathematical signal processing techniques to generate
detailed information on the fluid in the pipeline. In addition to offering
an inexpensive, non-intrusive solution, a number of key control
advantages are gained by providing information such as total volumetric
and mass flowrate, liquid and gas phase velocities, slug expected
arrival time and slug volume.
LIC
PIC
SEPARATOR
WATER
TO
HYDROCYCLONES
LIC
COMPRESSOR
OIL
GAS
OPC
Server
g-SSC
MODE ssA24
DCS Interface
WATER
TO
HYDROCYCLONES
ssA20 Operating Mode PT
ssA24 Operating Mode
DCS
Mode ssA24 is similar to mode ssA20 with the main difference being
that the primary input is from the riser DP.
Genesis Oil and Gas Consultants Limited, 3 Queens Gate, Aberdeen, AB15 5YL
RISER
PT PT
g-SSC
LIC
PIC
SEPARATOR
LIC
COMPRESSOR
OIL
GAS

g-SSC : The Process
The basis for g-SSC is advanced control algorithms and advanced
slug recognition algorithms.
The selection of the optimum configuration, operating mode,
algorithms and the setup, configuration and testing of the controller
is system specific. To ensure optimal performance it is important to
note that the g-SSC is part of a complete service. Coupling the
subsea, multi-phase hydraulics with the topsides control system
must be achieved prior to establishing optimum design of the system.
The Genesis g-SSC service is summarised below.
1
Data
Collection
2
Modelling &
Verification
3
Offline Controller
Configuration
4
Installation &
Commissioning
5
Operating
Support
g-SSC : Applications
Although we recognise that every system is different, we have tested
the g-SSC on a number of applications. These include:
Single well, single riser systems
Multiple flowline, multiple riser systems
Vertical risers
Catenary riser
Deepwater (tested to 1500m)
g-SSC : Controller Details
Adaptive Control
The controller is designed to operate across the entire operating
envelope of the system; varying well line up, GOR and water cut. This
is achieved by self tuning algorithms that are continuously monitoring
the key parameters and manipulating the control system tuning
configuration.
Initialization Routine
In addition to the standard automatic and manual operating modes,
the system also has an initialization mode. This mode allows the
controller to stabilise the system in a controlled manner, ensuring that
the system operates in the most stable regime.
Multiple Operating Modes
g-SSC can be configured to operate using input data from different
sources. For example, the controller has algorithms to prevent SRBS
R
using inputs from either: TESPAR , a multi phase meter or differential
pressure. The controller can simply be configured to suit the clientís
requirements and the available instrumentation.
Auto-recover From Operational Trips
The control algorithm has a ìrecovery modeî allowing automatic slug
suppression. This might occur if the control of the valve is temporarily
lost, (for example, after a topsides trip or confirmed fire and gas alert).
Anti-trip Functionality
The controller can be configured with rule based anti-trip logic. This
logic is designed to prevent the system tripping and centres around
rates of level and pressure increase in the separator, separator volume
etc.
Web Based Monitoring
Due to the complexity and dynamics of slug suppression, Genesis
offer a web based monitoring system. This will allow the controller to
be continually monitored remotely and any required changes can be
immediately advised to offshore.
Off-line configuration and Operator Training
The g-SSC is configured for each riser using a combined subsea
pipeline - topsides dynamic model, (Olga and Hysys.Dynamics). This
dynamic simulation can also be used for off-site operator training prior
to the installation of the g-SSC.
For further information contact Colin Manson
Tel: +44 (0)1224 201209, Fax: +44 (0)1224 201222, e-mail: colin.manson@genesisoilandgas.com