April 2008

Process Automation

Hot oil, cool control

New Zealand petrochem site commissions advanced, flexible control system strategy to pump first oil


  • Petrochem site needs advanced controls strategy to pump waxy solid out of ground.
  • Company calls on flexible control system strategy for temperature control.
  • Advanced system more operator friendly and flexible for add-ons down the road.
By Ellen Fussell Policastro

A mile beneath the hills of western New Zealand lies a vast reserve of solid, waxy oil. Unlike the familiar smooth, dark liquid that gushes from the ground, this oil requires heating and softening before extraction. Austral Pacific Energy Ltd., owner of the Cheal oil field, wanted to build a production station that would speed time-to-first-oil, one of the industry's most important metrics. This begins with the initial decision to drill and culminates when the station begins pumping crude oil.

The challenge was to begin the process with an advanced, flexible control system strategy that users could learn right away. Beyond speed, the company needed a sophisticated, integrated technology that could control and monitor everything from oil temperature to equipment performance, while capturing the data for complying with rigid regulatory requirements.

Advanced control to extract heat

A petrochemical site involves an advanced controls strategy, but the oil field needed a system reliable enough to help reduce downtime and flexible enough to easily expand. "Geologically, it's a difficult formation; this wasn't a standard oil production facility," said Greg Chapman, technical director at Engineering Control Limited (ECL), Cheal's systems integrator.

The oil begins as a tarry wax about 40˚C, so the process had to be kept hot at high pressures. "The oil sets to solid wax, so from a production point of view, the system control strategy had to be advanced and very flexible because they weren't sure how they would get the oil out of this geological formation," Chapman said. "So we were able to provide a flexible and powerful system, but one that was simple and easy to operate with a lot of feedback."

"The site can only handle around five hours of downtime before it begins to lose heat, and if all heat is lost, it takes up to two weeks to heat the wells up to the desired temperature," said Alan Hooker, an instrument and electrical engineer with Independent Technology Ltd. (ITL), the engineering procurement and construction contractor hired to design and build the station.

Heat begins the complex oil extraction and production process. Two centrifugal pumps powered by 350-kilowatt motors inject 115˚C water a mile beneath the surface, softening the oil. An application of continuous heat prevents the oil from re-solidifying as it ascends. The fluid exits the site's four wells and then travels to a separator drum. There, the oil, water, and natural gas divide as their densities dictate. A pump forces the separated water back down the wells, and a pipeline exports the separated gas to another production station for further processing.

Looks, feels like DCS

Austral Pacific wanted a system with distributed control system (DCS) functionality, "as well as the overall look and feel of a DCS system," said Guy Heaysman, managing director of ECL. As traditional DCS systems can be complicated and inflexible to integrate with other equipment and systems, they looked for a less costly system that would provide greater operational flexibility and a global view of their remote sites. They selected a control system based on automation integrated architecture.

Because this was an ongoing project, users needed an easy way to keep adding to the platform, said Heaysman. "The nature of the process made it difficult to control, so having something that was flexible and that could be modified online without interruption was important," he said.

The company's goal was to accelerate production, so Austral Pacific started production two months early, applied a single-control platform for discrete and process applications with open interfaces, and added well heads to the oil station as it expanded.

The integrated architecture system uses sophisticated control, networking, information, and visualization technologies to consolidate the full range of the oil field's needs. As part of the integrated architecture, the company selected programmable automation controllers that would provide capabilities of a traditional DCS system, but that would be multi-disciplined, meaning they could manage thousands of discrete, process, and safety I/O points using a single platform.

The controllers help "lower the cost of ownership, provide better flexibility, and offer more scalability than a traditional DCS system," Hooker said. The open architecture of the controllers, software, and other automation equipment "helps give Cheal the versatility to integrate field instrumentation and equipment from other vendors."

Users get it

The configuration tool helped ECL leverage a library of built-in process control instructions. Also, user-defined add-on instructions helped reduce upfront engineering and design time for ITL and ECL. "In addition to being simple to configure, the software's neatly laid-out programming code makes it easier for users to diagnose problems and make changes down the road," Heaysman said. "The system uses tag-based memory, which means all the physical addresses are in real-world terms like 'Well 3 sensor'" that people throughout the enterprise can understand, he said.

One of the common control philosophies in petrochemical is to make sure the equipment is familiar to operators. "We did training in house on a simulator system as well as ongoing live training on the plant as part of commissioning handover," Chapman said. "So it was two-phased and relatively straightforward. We worked to make it user friendly from an operator's point of view. So it's an easy stepping stone for them to use the DCS we implemented as opposed to common systems they used within oil and gas."

The integrated production and performance suite also sits at the core of Cheal's information handling capabilities. The software, which is tightly integrated with the PAC controllers, provides performance, visibility, and data management capabilities to operators at the Cheal production station.

The software gives their industrial computers a complete view of the oil field. Designed for supervisory-level monitoring, its scalable architecture supports distributed-server/multi-user applications. The software gives pager-toting field operators remote access to the control system equipment and instrumentation.

To supply operators and geologists with the information they need to make business decisions and to produce required regulatory reports, the transaction manager stores data generated by the controller and converts it to a spreadsheet. "Operators gain production information about the site's pumps, motors, flow rate, vibrations, pressures, and temperature so they can manage and trend the information as well as monitor performance," Hooker said. "Access to this data is crucial to maintaining reliability."

If an emergency situation arises, controllers at the oil field can automatically send out an alarm to pagers in user-defined situations. Tying the new system to the company's server technology helps field instrumentation send information back to the controllers. These field devices measure flow, temperature, and other process metrics, then send data to the controller through a 4-20mA connection.

To ease on-site system monitoring, an EtherNet/IP network transfers information from five remote-site pipelines to a human-machine interface. Cheal's three networks support a common language, the common industrial protocol. This commonality seamlessly connects production devices to the rest of the enterprise.

Faster first oil

Despite the Cheal oil field's complex production process, it achieved quick time-to-first-oil production 10 months after the company signed on for the new system. Typically, a production site of this size can take up to 12 months. "The integrated control system helped accelerate setup and streamline the intensive commissioning process," Heaysman said.

Configuring the system to Cheal's specifications went just as smoothly. With the integrated architecture, Austral Pacific simplified the configuration process by simultaneously addressing safety, process, and control disciplines. Also, tight integration of the HMI and controllers helped reduce programming errors, as they only had to make changes once so they were reflected throughout the enterprise.

Now that oil production is underway, the system requires only one or two on-site operators. The reliable production station helped reduce downtime, a critical outcome for a process dependent on keeping the site heated at all times. Local support from its distributor, systems integrator, and vendor simplifies technical support management, helps reduce downtime, and improves productivity of the complex operation.

Austral Pacific achieved a lower cost of ownership than a traditional DCS system could offer because of the seamless interaction between controllers, engineering and visualization tools, networking capabilities, and field instrumentation. Austral Pacific immediately benefited from its system's inherent flexibility when geologists discovered a nearby oil field shortly after the control system was programmed. Due to the scalability of the integrated architecture, Austral Pacific quickly incorporated the Cheal B site into its existing control system.

Friendly results bring more sites

Cheal implemented the advanced control strategy in minimum time, which has enabled them to achieve production rates from a difficult geological formation. "They have another full well site, and they're drilling another two oil wells at Cheal," Chapman said. "They're also looking at bringing on a remote site to the system. So, ongoing expansion is in process."

The biggest benefit of the entire project was using a company with specific oil and gas experience, Chapman said. "We were able to deliver a product that matched the user's needs, configuration, and commissioning expertise to actually deliver a system that was operator friendly," he said. "The advanced control strategy was highly tuned to oil and gas, and it was operator friendly with feedback, startup permissives, reporting, alarm reporting, emergency shutdown, and trips."

"We involved one of the senior vendor software engineers to get the platform correct right from the start. So it was money well spent. If we were to do anything differently, it might have been to install a few more operator stations," Heaysman said.

"We upgraded PCs to be dual screens," Chapman said. "From an operator's point of view, it has twice as much vision. And the cost benefit of that was significant. In future projects, we'll quote that from the start."


Ellen Fussell Policastro is the associate editor of InTech.  Her e-mail is efussellpolicastro@isa.org.