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7 interesting themes in flow measurement

I make an annual visit to several conferences and events focused on innovation in the world of oil and gas to keep my knowledge up-to-date and to meet with influential people in the industry. As always, last year, I’ve been able to learn a lot. In this case, specifically about the developments in flow measurement. Because it’s a shame to keep this knowledge to myself, I present you here with 7 themes that are currently playing a big role in the upstream sector.

By Hans R.E. van Maanen, PhD.

1. Oil price
There has, logically, been much ‘to do’ about low oil prices of late. According to a speaker at the North Sea Flow Measurement Workshop in Norway, this is due to several factors: the production of shale gas and oil in the United States, the expectation that that oil production in Iran will increase in the coming years, and, the high production level in Saudi Arabia. The speaker expects a more rapid increase in oil prices in the years ahead than many other experts. In his view, the global economy is growing rapidly, and an increased energy consumption in emerging countries – such as India – will have a big CO2 footprint. Whether his vision becomes reality, remains to be seen. The future, is in fact, difficult to predict.

2. Measurement of “wet-gas”
The use of ultrasonic (US) flow meters in liquid gas applications is another theme that has garnered much attention. The problem with the use of these meters is the liquid phase changes caused in the (local) velocity of sound; the quality of the transmitted signals is reduced, and a non-symmetrical speed profile occurs. The interpretation of the data of each individual “sound path” is more difficult. There are tests known for different types of US Flow Meters for gas. The result of these tests shows that the design of the selected meter, and the choice of the chords (sound paths through the pipe) are of great importance to the response of the meter to the liquid in the flow. The researchers were able to make a reasonable adjustment to the higher values of the Lockhart-Martinelli (LM) parameter. However, there needs to be even more research done before these meters can be used in practice.

3. Flow conditioning by US gas flow-rate meters
In addition, there is much discussion about the sub-optimum inflow of US meters. Flow conditioning can help here, but it is often not enough. The conditioners also make lots of noise and that lowers the quality of the primary measurements. The best solution is to set them up so that the measuring stations for the US meters are as favourable as possible.

4. Standards
An idea that appeals to me greatly, is the use of diagnostics in the standards for flow-rate meters. Such information is now rarely used in order to determine the quality of data from a meter. Whether that is actually coming, remains to be seen: in practice, the changing of standards is not easy.

5. Lay-out
An interesting paper published recently discusses the design of a revenue (export) measuring station, in this case of a station on the bottom of the sea. The author proposes to use three (identical) meters in a series: an “operational” meter, a “master meter” and a “reserve” meter. If one of the three meters goes down, the other two are still in a position to proceed with the measurement. While this is an interesting idea, certainly from a cost perspective, there lies a great danger or a plausible chance of (systematic) drift of the meters, for example due to contamination of the meters. If the main meter is only used as a control meter for the operational meter, then gradual change in the operational meter can be noted.

6. Multiphase flow meters
The integration of multiphase flow meters (MOM) in the entire data acquisition process, as is the case in the control system, is an item that deserves attention from the industry. Through increased use of diagnostic data, there is more confidence in the reliability of data from MPFM programs. It now awaits further results. During a recent workshop a practical application of MPFM was mentioned, wherein the known pros and cons came to light. One of the difficulties, for example, is their “subsea” use.

7. Monitoring from the wells
The well flow-rate data are essential in order to economically be able to optimize the recovery of hydrocarbons from the oil reservoir. However, a continuous stream of data obtained from the MPFM’s is even more valuable because it helps determine the best reservoir model. A new study recommends using down-hole flow rate measurements in order to obtain additional information. In addition, there are other mathematical tools that can improve the quality of the results. An example of this is the so-called Kalman filter. The advantage of this filter is that it uses “history” in order to improve the prediction models for the future values. This is certainly a development to keep an eye out for future applications.