Advanced Capacitance – An Alternative to Nucleonic Instrumentation

Despite being a well-established instrumentation for oil and water separators, Nucleonic instrumentation comes with several challenges. This article outlines the main challenges, as well as introduces an alternative solution that better meet the present market expectations of digitalization.

The Digital Transition

The oil and gas industry is in continuous development and transformation. There are new powerful technologies increasing automation, productivity and safety, whilst at the same time reducing unit cost and labour force. The digital revolution is all about unlocking the power of data to generate value. Thus, having instrumentation that allows you to make data-driven decisions has become more important now than ever.

Today, there seems to be a natural tendency to choose advanced instrumentation also for simpler applications, as it is viewed as a good investment; preparing you for the challenges you might face in the future. In addition, advanced instrumentation provides you with higher quality data to feed into your digital twin. Currently, there is a focus on automation and digital solutions to boost productivity. Consequently, the quantity and quality of the data has become fundamental.

Complex fluids

In the upstream stage of oil production, the fluids are unprocessed; meaning you deal with several different, uneven levels of fluids and solids. In addition, you face more complex challenges such as high temperature and high pressure.

In other words, the mix of several different fluids creates production uncertainties that can easily create challenges. Solving these challenges can take time, and consequently you are left with delays, reduced or loss of production and increased production costs.

As such, when dealing with complicated mixes of fluids, you require an advanced technology that provides you with high quality data, allowing you to read, as well as understand the structure of the layers, and their behaviour over time.

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Nucleonic instrumentation

Nucleonic instrumentation is perhaps the most established type of advanced instrumentation for oil and water separators. It has been around for decades and has been implemented in all the possible latitudes and applications.

This type of instrumentation uses gamma rays to measure fluid densities and then calculating the levels.

The gamma rays are sent through the fluids contained in a vessel from a gamma source (radioactive isotope) to a source container and a transmitter installed on the other side of the vessel.

Nucleonic instrumentation has a vast field application, is sold by multiple suppliers and has penetrated a range of different markets and environments. Despite being well established, Nucleonic instrumentation has quite a few challenges.

Challenges with Nucleonic

Nucleonic instrumentation measures density of the fluids. Considering that the difference in density of the fluids present within a vessel (e.g. water, oil and emulsions) is not so substantial, the measure is not of high accuracy or resolution.

Furthermore, Nucleonic technology requires frequent recalibration during normal operation of upstream separators. This is needed when the well stream changes its properties, such as density, API gravity, higher percentage of produced water or gas.

The recalibration requires a process shut down to completely empty the separator, subsequently causing numerous days of production loss. Nucleonic instrumentation therefore generates expensive maintenance activities. Due to its radioactive nature, there are also further cost-implications, such as:

• Special container for radioactive source transportation
• Special tool to install the radioactive elements
• Special equipment for maintenance of the radioactive elements
• Special measure to dispose the radioactive sources
• Portable radiation detectors, to verify that there is no emission of gamma rays outside of the vessels
• Licenses to procure, supply, install and dispose the radioactive sources
  

To avoid the challenges and expenses mentioned above, many operators are shifting from this technology to other equivalent solutions, like Advanced Capacitance.

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Advanced Capacitance

Advanced Capacitive consists of a rod insert directly into the fluid, where multiple sensors based on capacitance technology are installed. Each individual sensor is able to measure the dielectric constant (also called relative permittivity, εr) of the fluid, providing high visibility of the fluid layers inside the vessel.

The sensors can be distributed in a flexible way along the rod (typically more concentrated in the liquid section, less in the gas section of the vessel), providing a flexible and customizable resolution, that is typically higher in the liquid section, lower in the gas section.

In any operation, there is always a huge difference between the dielectric constant of the water, oil, emulsions, foam and gas. An advantage of Advanced Capacitance that measure this dielectric constant of the fluids is therefore that it is very accurate. Furthermore, it provides you data of high resolution, giving you clear visibility of the layers inside the vessel.

Advanced Capacitance technology is very competitive in dealing with tight emulsions, long settling times, severe foaming and heavy/high viscosity fluids. The fast response time makes it ideal also for separation processes with small separator tanks and where the fluid levels are changing rapidly. This type of instrumentation does not use any plastic insulation material, hence providing high robustness and reliability.

In contrast to Nucleonic Instrumentation, this option does not require any recalibration,
nor does it have all the extra risks and costs associated with radioactivity. Furthermore, Advanced Capacitance is considered a safe technology, in compliance with standard international import regulations. It is equipped with a self-cleaning system that allows to clean the sensors during normal operation of the separator. In other words, it does not require a process shut down to extract the profiler even during normal cleaning operations nor a separate measurement chamber with isolation valves.

Want to learn more about Advanced Capacitance? Check out this video!

Conclusion

Capacitance technology is the preferred choice when the crude oil is heavy and viscous, as this introduces complex and layers and poorly defined levels in production separators. It is accurate, providing you with data of high resolution to feed into your digital twin. It does not use any radioactive sources, making it a safe, cost-effective choice in alignment with international export and import regulations.