In the oil and gas industry, allocation:
…refers to practices of breaking down measures of quantities of extracted hydrocarbons across various contributing sources.
Emerson’s Mehmet Duzen shared a case study with the readers of Flow Control magazine. The article, TURNKEY Natural Gas Measurement, is about the gas metering, allocation and analysis system delivered to BOTAS, the state-owned oil & gas company in Turkey.
This system, which includes a 42-inch Daniel ultrasonic flowmeter, one of the largest in the world, as well as a gas chromatograph with controller, flow computers, temperature and pressure transmitters—all delivered as a turnkey solution, is used to perform gas pipeline allocation measurements.
A key element to reduce project risk was to have one automation supplier responsible for the allocation system:
…the Erzincan system was delivered as a complete package that was designed, configured, and commissioned by [Emerson’s] Daniel Measurement and Control (www.Daniel.com).
Here’s one example of how the project team shared technical expertise to improve project economics.
Daniel worked with BOTAS to perform calculations that allowed a reduction in the line size from 46 inches to 42 inches, a change that resulted in substantial savings without affecting the system’s design pressure.
The allocation system uses a gas ultrasonic flowmeter, which:
…are widely used in natural gas industry for custody transfer and other critical applications because they cause no pressure drop, which is a critical parameter, especially on compressor station applications. Also, they are immune to problems caused by contaminants, have no moving parts, and offer enhanced diagnostic capabilities.
In an earlier post, Finding the Lost Flow with Ultrasonic Technology and Remote Expertise, I described how ultrasonic flow measurement technology works in order to measure volumetric flow.
To get the components on the natural gas stream, a gas chromatograph analyzes the gas. It:
…reports the energy and provides the detailed gas composition data that are used for the volumetric flow measurement.
The instrumentation for the allocation system included:
- Four-path 42-inch Emerson Daniel SeniorSonic ultrasonic flowmeter
- Emerson Rosemount pressure and temperature transmitters
- Two Emerson Daniel flow computers
- Emerson Daniel 2350A gas chromatograph controller
- Emerson Daniel Model 570 Danalyzer gas chromatograph (GC) complete with gas and helium bottles, as well as regulators
You’ll want to read the article to see the architecture, redundancy, and communications path of the instrumentation with the pipeline’s distributed control system (DCS).
Mehmet described the startup and commissioning services performed by the Daniel team:
The complete system, including the 42-inch gas ultrasonic meter and the gas chromatograph were configured with the two S600+ flow computers via RS-485 Modbus communications, and the commissioning was successfully completed.
Performance results from the Compressor Station to date:
…shows that the meter is operating within the stated accuracy limits of +\- 1.0 percent.