Rockwell Automation’s Zack Munk blogged recently on the relative merits of RTUs and PLCs at the well site. Some operators have as many as 50 wells on a single pad, placing ‘much greater demands on control systems.’ Time is ripe for a reevaluation of technology options. For decades, the remote terminal unit (RTU) was the go-to technology in the upstream. RTUs are rugged, low power and could handle Scada systems’ low bandwidth needs.
But the modern multi-well pad is pushing the limits of RTU technology and producers need a more performant solution such as a programmable logic controller (PLC). PLC originate in the plant/factory environment rather than the ‘inhospitable and harsh’ environments of the oil field. But increasingly, well pads have environmentally controlled buildings or enclosures, along with ping and power, the perfect environment for PLCs.
Munk believes that a ‘modular and scalable’ PLC control architecture addresses the challenges of legacy RTUs. PLCs can be configured in many ways, allowing operators to monitor and control a wide variety of field instruments. PLCs support communications across different networks while libraries of pre-developed, documented code allow for rapid onsite configuration without specialist programming skills.
Multi-well pads have made data and application requirements in upstream operations greater than ever. RTUs remain a feasible option, but their memory limitations, added maintenance requirements and overall higher production costs provide a strong incentive for operators to consider a better alternative.
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