The JOURNAL

In the heart of the Brazilian rainforest, 38 flow streams of natural gas are transferred to an oil treatment plant owned by Petrobras.

The JOURNAL

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Calculated Success

Oil-treatment company chooses in-rack flow computers to help it meet new regulations for its Brazilian natural gas operation.

By Danetta Bramhall, ProSoft Technology

The Urucu province is the second largest natural gas reserve in Brazil, with an average daily production of more than 5 million cubic meters per day. In the heart of the Brazilian rainforest, 38 flow streams of natural gas are transferred to an oil treatment plant owned by Petrobras. When the National Oil Agency published new regulations requiring more accurate measurements for oil-volume transfer, Petrobras needed to review its existing installations and specify equipment compliant with these regulations.

“If we had chosen the classic model of dedicated flow computers, the costs and engineering to present the results would be very high,” says Francisco Carlos Campana Aragon, senior equipment engineer for Petrobras. “This is because for the implementation of 68 EMEDs [dedicated flow computers], we had an average cost of U.S.$40,000 per unit. The units would vary from 4 inches to 10 inches, and pressure class varied between 300# and 2500# [19 units].”

This high cost eliminated this option for Petrobras. Instead, Aragon implemented Rockwell Automation Encompass Product Partner ProSoft Technology’s in-rack flow computers for Allen-Bradley programmable logic controller (PLC) and SLC platforms.

How In-Rack Flow Computers Helped

Aragon installed four 2100-AGA modules in an eight-slot Allen-Bradley chassis (PLC-5/80) to calculate volume for the 38 flow streams transferred through the oil treatment plant. These modules continuously transfer calculation results to the PLC, providing total compliance with the API 21.1 standard.

The gas then leaves the oil treatment plant and transfers 12 km to the oil extraction plant. There, 16 flow computers (MVI46-AFC) calculate flow rates and gas volumes. MVI46-AFC modules communicate through the backplane with an Allen-Bradley SLC 5/03 for each extraction plant.

“Thanks to the interaction between ProSoft’s MVI46-AFC in-chassis flow computer module and the SLC processor, we could implement an automated system for calculation and presentation of results totally compatible with the level of automation used in our plant,” Aragon explains. “The cost would have been much higher using the classic dedicated flow computers than those obtained through the in-chassis flow computer module.”

Flow computer computation involves two stages. First, the oil is measured with the gas “in solution.” Then, three 2100-AGA modules transfer results to the PLC data memory where the gas amount is subtracted from oil volume, which the module supplies. This is accomplished by using a correlation involving gas density (also supplied by the module), oil density, pressure and temperature.

“The test system for each extraction plant was only possible totally automatically without volume loss because of the ProSoft flow computers and the PLC and SLC processors,” Aragon says.

“If we had chosen the old solutions using EMEDs, the costs would have been much greater. The ProSoft modules are a success story for us. The integration between the MVI46-AFC and the 2100-AGA flow computers along with the flexibility of the SLC and PLC processors were the decisive factor in that success,” he adds.

Economic Development in the Works

Natural gas from the Urucu field is shipped via pipeline 280 km to Coari on the Solimoes River. Other projects are being considered for future expansion. Such projects pave the way for economic and industrial development, generating jobs and reducing the price of electricity by approximately 50% lower than the current rates in the region.

For more information about Rockwell Automation Encompass Product Partner ProSoft Technology, visit www.rockwellautomation.com/go/p-prosoft.