Calorific value refers to the energy content of the natural gas, and is calculated from the natural gas composition using ISO 6976.
A company purchasing natural gas is paying for the energy content of the gas, and will expect quality for the purchased product. The international benchmark for the sale of natural gas is that the calorific value be specified to within 0.1 per cent of the true calorific value. Meeting this benchmark is a significant measurement challenge.
If this requirement is not met it could result in damage to a company’s reputation, a decrease in further growth opportunities, and will jeopardise return on investment across revenue, plant and equipment.
Gas calibration standards are gas mixtures with known composition. These are used during gas analysis to assign compositions to gas samples collected during processing and transport; ultimately, the standards are used to assign the calorific value of exported LNG.Article continues below…
The tolerances on most commercial gas standards are too large for LNG export – meaning that the composition and calorific values are simply not accurate enough. It is only the calibration standards that are produced under the most stringent manufacturing conditions that will guarantee optimum results – notably consistent and correct calorific values that meet international requirements. The National Measurement Institute (NMI) of Australia manufactures gas standards with very tight tolerances, and these standards will deliver measurement results robust enough to comply with international trade requirements.
How can Australia meet the standard?
Australia’s LNG export industry is relatively young compared with other nations, and as such, much can be learned from other countries that already have a long history of cross-border trade in natural gas.
This is certainly the case in the Asia-Pacific region, where most Australian LNG is sold. All gas imported into South Korea is tested by KOGAS and Korea Gas Safety. Both companies purchase their calibration standards from the Korea Research Institute of Standards and Science (the NMI of South Korea). This gives these companies the confidence that they are making consistently correct measurements of calorific value, allowing them to operate from a position of strength.
For Australian gas exports to meet the exact demands of international purchasers, investment in quality calibration standards is essential. In addition, measurements must also be periodically checked to ensure that they remain accurate. Various factors could make measurements drift with time, and changes may go unnoticed, until complaints are received from customers. The best method for checking the accuracy of measurement results is through participating in proficiency testing.
Between October 2010 and May 2012, the NMI compiled results for proficiency testing of CSG, LNG, pipeline and raw natural gas, and only 10 out of 43 participants (23 per cent) met the international benchmark for exported gas.
ConocoPhillips Australia is an Australian company using the right approach at its Darwin LNG plant. The company sources calibration standards from the NMI for testing LNG and gas products, and also for monitoring plant performance. It then takes part in proficiency testing to monitor the accuracy of measurements for their international customers.
International partners have defined their expectations around what is an acceptable tolerance for import gas measurements. Therefore, it is important to consider the damage to business and trade when the product specified by the exporter does not measure up to international import standards. Such a scenario will have devastating results, making investment in the right measurements an essential insurance.