Dramatically falling oil prices were expected to take a big toll on the rate of North American shale exploration this year. Though a modest rise in prices kept drilling and volume production high, profit margins are still under particular scrutiny.
Using horizontal fracturing technology, shale wells produce high-energy natural gas—also called associate petroleum gas—along with crude oil. Most shale operators elect to burn the high-energy natural gas on site with flaring applications. However, not only are flaring regulations becoming stronger in these states, the gas contains valuable commodities such as methane, butane and propane that shale companies could process for on-site repurposing or for selling.
Enter Pioneer Energy, a vertically integrated engineering services company in the oil and gas industry, and its Mobile Alkane Gas Separator (MAGS), which processes the raw natural gas. Though the assumption was that the natural gas deposits would be 100 percent methane, Pioneer found that was not the case. And after a year of R&D, Pioneer introduced this mobile processing application as a way to reduce material costs for drilling operations, increase revenue and reduce the environmental concerns with gas flaring.
An engineering challenge for Pioneer was to reproduce the processing capabilities of an entire gas processing plant in a single mobile system that could fit onto a truck trailer—making it more accessible to an industry that typically operates in some of the remotest parts of the U.S., away from established oil fields and processing operations.
The system fits onto a 40-ft dropdeck trailer for delivery and, once installed, processes wet gas saturated with hydrocarbon vapor. It uses compression, dehydration and refrigeration to separate the original hydrocarbon stream into refined energy products, including methane, ethane and natural gas liquids (NGLs) such as propane and butane. These hefty units can process up to 333,000 cubic ft of gas in 24 hours with one unit, according to Andrew Young, lead controls engineer for Pioneer Energy.
MAGS is a complex system, and needed a control system to make everything work together. An average processing unit uses about 150 I/Os. But Young also needed hardware that would be compact and reliable, and have low power requirements and support for a wide range of I/O signals and communication protocols.
He chose SNAP PAC controllers from Opto 22. “To interface with all the equipment on MAGS, we use nearly all of Opto 22’s I/O modules plus the SNAP PAC system’s built-in Modbus protocol support,” Young says. The Opto 22 system automates the entire system, monitoring and controlling temperature sensors, flowmeters, pressure transmitters, control valves, the generator, refrigeration compressors, a gas chromatograph, process heaters, and other devices.
The system is also scalable. Oil contractors take preliminary measurements on the amount of gas expected in a wellhead, from which Pioneer Energy can match on-site processing needs. But then MAGS has the flexibility to scale down as time goes on, Young says. “We can deploy two mobile processing systems initially and, in six months, we’ll be able to pull one off (due to well depletion), redeploy the capital and leave a single system to continue to serve the well as it drops down in volume,” he says.
Given the remote locations of the shale sites, the reliability and communication capabilities of Opto 22’s system are key to allowing a MAGS system to operate autonomously, Young says. Pioneer provides remote monitoring of the onsite processing from Lakewood, Colo.
Creating the NGLs requires moderate pressure and cold temperatures, but is also dependent on removing ethane—a negative economic value—by condensing it into a liquid and rejecting it in a stripping column. The system’s ability to refrigerate natural gas at a very cold temperature is also important to produce fuel-grade methane and NGL products that meet commercial standards for use and transport.
This complex processing is controlled and monitored via an OPC-DA 2.0 compliant server, called OptoOPCServer, and it communicates only to Opto 22 control and I/O systems onboard at these processing units. “We have multiple workstations in the mission control room and operators continuously receive data from this OPC server,” Young says.
Pioneer Energy also provides technician services for minor maintenance of these MAGS units at remote sites. The company leans on Opto 22’s groov mobile monitoring to provide field technicians monitoring and control onsite via mobile devices.
“Now our service technicians in the Bakken oilfield have 4G AT&T tablets that link to the groov server, which is connected to the OPC server,” Young says. “They can see real-time operations as they’re in route to a site to do a service call.”
Pioneer currently has five MAGS systems in the Bakken Shale fields in North Dakota and Montana, and this demonstration of remote monitoring is essential for further growth, Young says. “The data package with the automation platform is very lightweight, and so our data concepts have been reliable,” he says. “It has actually opened up the global market in developing countries, where they don’t have typical fiber/copper infrastructure. They have cellphone networks.”
Initial applications with MAGS has been with hydraulic fracturing, but oil and gas producers are also interested in pipeline applications, offshore operations, older conventional wells and even international applications, according to Pioneer Energy.
