Energy Firm Turns Oilfield Gas Flares Into Income

Whenever crude oil is extracted, water, sand and natural gas are part of the mixture. And when large reserves were discovered in the Ixachi field south of Veracruz, Mexico, extracting and transporting the oil was the relatively easy part. Separating and shipping the oil via pipeline is always straightforward. Managing the natural gas is another matter.

“Oil is handled like a liquid and transported by pipeline or truck,” says Mudar Jamal Eddin, engineering director, Grupo Nuvoil. “Natural gas must be processed and compressed before it can be transported in commercial pipelines.”

If a processing plant isn’t accessible, producers typically ignite or “flare” the natural gas to dispose of it. This practice is wasteful and raises environmental concerns. Flaring also represents a lost source of revenue for oilfield operators. Therefore, Ixachi needed to make the most of scarce resources.

To keep flaring to a minimum and maximize returns, Ixachi operators asked Nuvoil to deliver a gas-conditioning plant near the oilfield as quickly as possible. Nuvoil is a major energy services and solutions provider headquartered in Veracruz.

Compressed Schedule, Complex Process 

The scope of work for the gas-conditioning plant included engineering, procurement and construction — and operation and maintenance of the completed plant. Located on 32 acres about 10 miles from the well pad, the completed Papan Gas Processing Plant was specified to process 345 million standard cubic feet (345 MMSCFD) of natural gas per day.

“While the timeline was challenging, we knew we had the capacity to meet our customer’s needs,” Eddin says. “We had built similar plants in the past — and flare avoidance is our core business.”

To meet customer requirements, Nuvoil designed a cryogenic gas processing system. The complexity of the system is difficult to overstate.

At the wellhead, oil, water, sand and natural gas are separated. The resulting “sour gas,” which contains sulfur, enters the Papan Gas Processing Plant at about 200°F. In the first step, the gas is chilled to 120°F and residual sand and dirt are separated.

Next, the gas enters the sweetening plant, where sulfur is removed — and then moves to a molecular sieve dehydration system, where humidity is absorbed. In the subsequent chilling process, the gas temperature drops to about -121°F.

“Chilling triggers gas condensation,” Eddin explains. “As a result, we can remove LPG (propane/butanes) and other hydrocarbons. What remains is almost pure methane and ethane.”

Finally, the gas is compressed for transport via commercial pipelines.

Managing 3,000+ Data Points

To speed implementation of the plant, Nuvoil chose a control system integrator they had successfully worked with in the past, Ascend Automation & Controls, a Bronze OEM Partner in the Rockwell Automation PartnerNework™ program. Ascend is a division of CAM Integrated Solutions.

“Our company is very familiar with gas conditioning systems,” says Horacio Tinoco, vice president, Ascend Automation & Controls. “We developed a control system for Nuvoil about 11 years ago. Of course, the new system enables even more sophisticated and efficient operation.”

The Rockwell Automation control platform is based on Allen‑Bradley^® ControlLogix^® process controllers and a FactoryTalk^® View HMI. To ease system monitoring, Nuvoil relies on a video wall in the plant featuring twelve 55-in. displays and four operator workstations in the control room.

To manage the process, more than 3,000 instruments are physically connected to the system – and nearly 150 PID loops are included.

“In a complex system like this, the data points multiply rapidly,” says Tinoco. “Using data trending, Nuvoil can produce reports to support operations, maintenance or custody transfer.”

In addition, Ascend will be adding  software to the system soon.