What kind of data does an international oil drilling operation need? The kind Patti Engineering devised using Siemens Step 7 engineering and PLC-based system for safer, more robust drilling.
In oil and gas drilling, taking quick actions as markets change can make the difference between good profits or major losses. An international drilling operator determined that it needed to gather more data and better monitor alarms to improve overall efficiency.
The company reached out to Patti Engineering to devise a high-level design and implement a PLC-based application for land rig drilling products used around the world. The Auburn Hills, MI-based control system integrator knew it had to provide quick development time to get the product implemented – and do so with easy to use, rugged equipment with advanced functionality.
Patti Engineering’s design team needed a strong controller for a data-rich drilling application. In today’s fast-paced oil and gas environment, there’s little development time for a quality, long lasting application, making PLCs a viable solution.
The developers focused on two things:
1. Data availability during the deployment and debug phase for fine-tuning and honing the system.
2. Alarm management for understanding alarms and analyzing preceding and following events.
“During product development, an important element is controlling costs,” said Steve Palmgren, Vice President of Texas operations for Patti Engineering. “There are two pieces to cost containment: hardware and development. You have single board computers and microcontrollers that are really cheap. However, it is very wide open and you have to develop all your diagnostics. You don’t have support systems like you get with a PLC.”
Picking the right PLC was important as developers decided how to upgrade aging equipment. Palmgren wanted straightforward programming so they could quickly develop a solution. The Siemens IM-151-8, ET200S-based PLC met the bill.
“When upgrading legacy equipment, serial interfacing is important because there is a lot of old equipment in the field talking RS 232, RS 422, RS 485, or there may be some custom code where a random packet stream was meant to be proprietary. The difficult task for an integrator is implementing all the previous functionality onto a PLC without standards,” Palmgren said.
This integration was accomplished with a third party application with TCP communications. TCP lets two hosts connect and exchange streams of data. The system handles regular character frames with packet sizes in the 500-to 1000 byte length, far larger than the 256 bytes of most serial cards.
Programming was a major concern. Pattie Engineering wanted to get the right software quickly while also giving the driller flexibility for the future.
“Structured Control Language (SCL) is another awesome tool in the Siemens PLC library. Most people will program a PLC in ladder logic, which is where its roots came from. But now we are able to process things at a faster rate with faster processors, we have linear programming languages like SCL that enable loops, indirect addressing, lookup tables, statements and searching,” Palmgren said.
Palmgren added that the Siemens PLC has pre-configured add-ons and cards that save engineering and development time. The software is also pre-configured for functions like PID control. The ability to tightly integrate hardware and software with pre-configured blocks reduces development time, and provides diagnostics for faster debugging.
The application from STEP 7 classic was moved into the Totally Integrated Automation (TIA) realm to get even more benefits. TIA permits efficient interoperability for all automation components.
“Using TIA, you have PID professional where you have a group of function blocks you can just drop in and start working with your PID,” Palmgren said. “Then you have modular PID and standard PID blocks which is what we primarily used. You have self-tuners, too. So you can drop another function block in and you can automatically tune your parameters, which is a huge time savings.”
Normally, land rig-based installations are several hours away from civilization, so capturing events is critical. The Siemens PLC saves the previous 25 seconds leading up to the alarm event and 5 seconds after the event. That came in handy when the team ran into a problem with variations at a remote site.
“We kept seeing a repeatable pattern in the control process,” Palmgren said. “It wasn’t a sine wave, but it was really close and it was cyclical with the process and the PID loop had to keep compensating for this. We diagnosed the problem with a Fourier series (Fourier series is a way to represent a wave-like function as the sum of simple sine waves) to track and plot what that pattern looked like. We then created a sine wave, aligned it, and then re-injected that sine wave into the PID loop as a disturbance variable. Now the PID loop only had to account for the variations along the sine wave. That greatly improved the process so we could fine-tune the PID loop to make it more accurate.”
The application’s large memory capacity also lets field service personnel analyze historical data for troubleshooting. The system captures 40 different parameters and variables in the system.
“In the beta phase of the project, we logged the same data sets from the memory card into a real-time database. At any point I could take a snapshot of the information, chart it and analyze any abnormalities. That helped us with solving problems before they occurred,” Palmgren said. “Now the tech can go into the field, connect wirelessly to the rig network, and access the data via the Open TCP connection for faster troubleshooting.”
Palmgren said the application went from conceptual product that had a high-level design through simulation and on to the first rig in three months.
“Our customer was extremely happy because we were able to get units out in the field. They launched units all over the world with a faster time to market.”
With the help of a powerful PLC, they were able to pull data at the right time to fine tune the applications and understand the nuances behind any alarms, yielding a more robust drilling solution.
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