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How do we make LNG measurements more accurate and reliable?

The industry loses millions of dollars daily, but yet have to realize it

Hans van Maanen

Recently, I had the privilege to speak at The European Flow Measurement Workshop. More than 200 participants from various countries around the world met in Noordwijk to discuss the measurement of flows, with a focus on the oil and gas industry. One issue was the accurate and reliable measurement of LNG (Liquefied Natural Gas). At present, the industry loses millions of dollars because the margins of error are (too) large. We have devised two optical techniques to improve the calibration of flow measurements.

A number of industry developments were discussed at the meeting in Noordwijk. For example, there was a lot of attention for one phase measurements and export measurements. Because now, in addition to export, import also occurs— i.e. natural gas—so export stations must be able to work in two directions. After all, measuring in two directions does not just happen. This is a very relevant topic for the Netherlands, since we are currently conserving the Groningen gas and therefore need to be supplied from abroad.

Another important aspect that came up during the many lectures, involved more and better usage of the so-called “diagnostics data” of flow meters. We, the employees of Hint, have been saying for some time that there is a profit to be gained here, and it is always good to hear that others also feel this way. One problem, however, is that these “diagnostics data” are often more extensive than the actual measurement data. This supports our plea to set up a separate system for this, in parallel with the data acquisition.

Large uncertainties
Another much discussed topic was the transport of LNG and the logistics that it involves. LNG is becoming increasingly popular; it is a relatively clean fuel and readily available. The technical infrastructure involved in LNG transport is still developing strongly. The uncertainties in LNG measurements are currently still large. As a customer, you have little choice but to believe what the vendor tells you about the quantities of LNG that he has loaded on the vessel’s departure. Compared to your own measurements when disembarking, the differences are still too big and must then be “settled”. You just have to trust that “the receipt” is correct, because there are no techniques available yet to determine the calorific values with great accuracy.

The problem with LNG
The LNG tanker at sea is a kind of blackbox. We don’t know exactly what happens to LNG during transport. This is because, with LNG, two problems emerge that you normally don’t encounter, and again the technology to tackle these problems has not yet taken full shape. With LNG, the focus is especially on calorific value – what does the gas produce if I’m going to burn it? This is more important than mass or volume. However, the gas composition varies by vendor, so it must be determined on a case-by-case basis. In addition, the composition changes in transportation: the lighter components evaporate. Also, the portion of the LNG that evaporates during transport is used to drive the tanker itself. This is smart, but it does have implications for the composition, which is not constant during the disembarkation.

Another problem specific to LNG, is that it is transported in a liquid form, at a temperature of -162 degrees Celsius. This extreme cold has quite a bit of influence on the materials and systems that come into contact with the LNG. As a result, the properties of normal flow meters are changed and their calibration can only be done on a very limited scale at this type of low temperatures. That undermines the confidence in these meters.

New techniques for verification
In my lecture at The European Flow Measurement Workshop, I have therefore argued for obtaining additional information to determine the composition. I also presented two ideas that we developed at Hint for the verification of LNG flow meters. These two optical techniques can, in our view, be of large-scale importance for the industry, but we cannot develop them by ourselves. At the meeting, I therefore tried to boost enthusiasm with other parties (companies but also research institutes and universities) about Hint’s plans and about setting up a consortium to elaborate on these plans and put them into practice. I received many positive comments, so I have high hopes that we will take the next step towards the development of these techniques. But this will not succeed without the support of the oil and gas companies themselves. After all, they will gain most from accurate measurements.

You’d think that everyone would prefer fair pay for what he gets. Not too much, nor too little. The opposite also applies for the LNG producer. Yet, very little attention is being paid to this problem by the industry. I don’t understand this, since oil and gas companies are paid based on what the meters indicate. And that can turn out quite negative. The industry should become aware of the millions of dollars it is losing on a daily basis, and pursue industry-transcending standards. In addition, it would have to invest in the development of techniques to make LNG measurements more accurate and reliable. Otherwise they will, literally and figuratively, pay the price.

Hans R.E. van Maanen, consultant at Hint