5 Telemetry/SCADA
Supervisory control and data acquisition (SCADA) is normally associated
with telemetry and wide area communications, for data gathering and control
over large production sites, pipelines, or corporate data from multiple
facilities. With telemetry, the bandwidth is often quite low and based on
telephone or local radio systems. SCADA systems are often optimized for
efficient use of the available bandwidth. Wide area communication operates
with wideband services, such as optical fibers and broadband internet.
Figure 32. SCADA system topology (typical)
Remote terminal units (RTU) or local controls systems on wells, wellhead
platforms, compressor and pump stations, are connected to the SCADA
111
system by means of the available communication media. SCADA systems
have many of the same functions as the control system, and the difference
between them is mainly their data architecture and use of communications.
8.2 Digital oilfield
In the oil and gas industry digital oilfield (DOF) is a generic term for new
solutions and technologies for operation, work processes and methods that
are being made possible by adopting innovations in information technology.
Other names such as Integrated Operations
(IO), E-Field, Smart Fields, iField and Integrated Asset Management are used for the same concept.
Intelligent Energy is a general umbrella term adopted by Society of
Petroleum Engineers (SPE).
Central to this concept is collaboration between people; where data,
information, knowledge shared between a number of parties in digital form.
This often supported by technologies such as video conferencing and
augmented reality for personnel in remote locations or in the field. In this
environment we add solutions for optimal performance, security,
maintenance.
Figure 33. Digital Oilfield
112
Optimal production targets and maximum utilization of production resources
are achieved through the use of several sources of information, such as
reservoir mass balance calculations and depletion strategies, well test
results and use of simulation models. This is made possible by linking skills,
data and tools together in real time – independent of location.
Some of the enabler technology areas are:
1. A system and communication IT infrastructure
2. Applications for remote operations and remote operations support
3. Reservoir management and drilling operations
4. Production optimization
5. Information management systems
6. Operation support and maintenance
8.2.1 Reservoir management and drilling operations
Solution for data acquisition, modeling
and visualization between facility
operators and central company experts
to provide:
• Drilling simulation and
visualization, automatic
diagnostics and decision
support, real-time measurements
while drilling in order to locate the best targets
• Reservoir models based on real-time reservoir data, analysis of 4D
seismic, in-situ measurements of changes. On-line integration with
well-serviced company data
• Optimization models for increased production, based on in-reservoir
properties during production, with decision support incorporated to
improve productivity
8.2.2 Production optimization
Optimizing the production or improving productivity is a complex problem. In
addition to the production optimization of the downhole, subsea and topside
process, one has to consider operational costs, hardware damage, reservoir
performance, environmental requirements and operational difficulties within
each well and/or topside. To further complicate optimization, the individual
challenges will change over time, e.g., reservoir behavior changes as an
effect of depletion, shutdown of wells due to slugging, failed sensors and the
change of efficiencies within the topside process system. Some of the
applications included in production optimization are:
113
• Flowline control to stabilize multiphase flow in gathering systems,
risers and flow lines.
• Well control that will stabilize and optimize gas lift and naturally
flowing wells. This application should prevent flow and pressure
surges while maintaining minimal backpressure and maintain
maximum production as well as continuing production at the
optimum lift gas rate.
• Gas-lift optimization is provided to ensure the best possible
distribution of lift-gas between gas lifted wells.
• Slug management helps mitigate variations in inflow impact. The
separation and hydrocarbon processing during startup, upset and
normal operation.
• Well monitoring systems (WMS) are used to estimate the flow rates
of oil, gas and water from all the individual wells in an oil field. The
real-time evaluation is based on data from available sensors in the
wells and flow lines.
• Hydrate prediction tools help to avoid hydrate formation, which may
occur if a subsea gathering system is allowed to cool down too much
before the necessary hydrate preventive actions are performed.
• Optimal operation is defined by a set of constraints in the wells and
production facilities. A constraint monitoring tool monitors the
closeness to all constraints. This provides decision support for
corrective actions needed to move current operation closer to its true
potential.
• Advanced control and optimization solutions to improve the
performance of product quality control, while adhering to operating
constraints. This is typically done with two technologies: model
predictive control to drive the process closer to operating targets,
and inferential measurement to increase the frequency of product
quality feedback information.
• Tuning tools are designed to optimize and properly maintain the
optimal setting of control loops in the process automation system.
8.2.3 Asset optimization and maintenance support
An asset optimization (AO) system reduces costly production disruptions by
enabling predictive maintenance. It records the maintenance history of an
asset and identifies potential problems to avert unscheduled shutdowns,
maximize up-time and operate closer to plant production prognoses. This
functionality supports maintenance workflow as the AO system
communicates with a maintenance system, often denoted as a computerized
maintenance management system (CMMS).
114
Figure 34. Computerized maintenance management system
Condition monitoring includes both structural monitoring and condition
monitoring for process equipment such as valves and rotating machinery.
For structural monitoring, the devices are corrosion meters (essentially
plates that corrode, so that corrosion may be metered), tension force meters
and free swinging strings. These statistics are logged to a central structure
condition monitoring system, to show what forces are acting against the
installation, and the effect those forces are having.
Condition monitoring of machinery is generally used for large rotating
apparatus, such as turbines, compressors, generators and large pumps.
Input devices are vibration meters, temperature (bearing, exhaust gases,
etc.), as well as the number of start/stops, running time, lubrication intervals
and over-current trip-outs. For other process equipment, such as valves, the
system can register closing times, flow and torque. A valve that exhibits a
negative trend in closing time or torque ("stiction") can be diagnosed. The
maintenance trigger is the mechanism whereby field device or equipment
monitor resident information, in the form of digital status signals or other
Asset Monitor
Maintenance Management
Create work order
Work order history
Maintenance status
Preventive maintenance,…
Operator
Heat Exchanger
Actuator/
Valve
Diagnosis
and
Status Data
Messenger CMMS*
Service staff
extern
Maximize the utilization of
plant assets over their lifecycle
Asset
Condition
Document
ERP-System
115
numerical or computed variables are interpreted to trigger a maintenance
request. A work order procedure is then automatically initiated in the CMMS.
Maintenance support functionality will plan maintenance, based on input
from condition monitoring systems, and a periodic maintenance plan. This
will allow the system to schedule personnel for such tasks as lubrication or
cleaning, and plan larger tasks such as turbine and compressor periodic
maintenance.
