Pumps & Systems, February 2009

How a monitoring alarm system with control and shutdown capabilities prevented costly pump damage and environmental hazards and made the job of the pump operator safer and easier. 

Figure 1Schlumberger Limited is a global oilfield and information services company with a major focus on the energy industry. The company delivers real-time technology services and solutions across industry markets that customers use to translate acquired data into useful information for improved decision making.

During the past several years, its coiled tubing drilling (CTD) operations in Alaska have been opening the door to a host of techniques for exposing bypassed oil reserves and enhancing well productivity. CTD uses a long, continuous length of pipe wound on a spool. The pipe is straightened prior to pushing it into a wellbore and recoiled to spool the pipe back onto the transport and storage spool. Because connection time is eliminated during tripping, the company uses coiled tubing so operations proceed quickly when compared with using a jointed pipe drilling rig. Nearly half of all new wells in North America's largest oilfield use coiled tubing for drilling.

Safety Top Priority

While the CDT system provided numerous benefits, including greater safety and efficiency, reduced environmental impact, minimized formation damage and improved drilling performance, operation managers at the Prudhoe Bay field in Alaska were seeking a customized integration system. They wanted to implement an automated backup for drilling technicians and operators, provide a backup controller for computer operations and standardize the operator interfaces on different pump equipment. Designing a customized system to meet these needs would create built-in redundancy for extra security and could save lives and money.

NST was contracted for a solution to this industrial challenge. NST, a National Instruments Select Integrator headquartered in New Mexico, designs and produces data acquisition and control systems for various industrial applications.

After evaluating the system, NST determined the key requirements to be reliability, ruggedness, embedded control, data logging and communication. Because the system required reliability and a mix of functionality such as data logging and embedded control, NST recommended using National Instruments LabVIEW Real-Time module running on an NI FieldPoint control bank. It worked with the company to design a computerized, soft pump integration system to act as a backup controller in case the host computer became disabled, idle or shut down.

Automation For Added Control

This soft pump integration system was composed of five major components-the personal computer, SPI control box, engine, transmission and pump. The heart of the system was the control box, which was designed using a module with digital inputs and outputs, analog inputs, two frequency to analog transducers and a battery-backed up power supply. The custom software delivered a standard control interface with user-configurable alarm monitoring and data logging capabilities. The control system communicates with a central monitoring system, which is equipped to perform remote shutdowns of any pump system on the entire network.

Numerous other safeguards were built into the system's design, including "watchdog" mode, which monitors all engine parameters and shuts down when one parameter exceeds pre-defined "normal limits." The system can monitor levels and automatically adjust the throttle to maintain certain pump levels. In addition, if the pump operator's laptop becomes disconnected, the control box kicks the engine transmission into neutral and idles the throttle. The control box continues to monitor engine parameters and shuts off the engine when levels exceed normal limits. The operator can retrieve the log entries when the laptop connection is restored.

If a different laptop is connected to the control box, the box will upload its settings to the new operator's laptop for control to continue. All calibration settings, alarm levels and control procedures are stored in the control box. The modules are hot swappable, which provides on-site maintenance with minimum downtime.

This system provides solutions for controlling and monitoring instrumentation, including water pumps, temperature controllers and drilling systems. Schlumberger uses these systems in Alaska and Malaysia.