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Nanotechnology-based surface-enhanced Raman spectroscopy is being used in the oil industry to better identify and analyze the chemicals it uses to treat oil. The new technology crucially enables chemical speciation analysis which is an important step in reducing the overall environmental impact of the oil industry.
The oil industry has a responsibility to minimize its environmental impact as much as possible, due to the relatively large proportion of blame it shares for environmental destruction through accidental and industrial pollution, carbon emissions, and fossil fuel extraction.
Recent advances in scale inhibitor analysis – presented to the virtual conference and exhibition of the Society of Petroleum Engineers in June 2020 – will enable the industry to better meet this environmental responsibility. Nanotechnology-based surface-enhanced Raman spectroscopy crucially allows for chemical speciation-based analysis, which is essential for understanding and minimizing pollutants in scale inhibitors.
What are the Problems with Scale?
Scale is the term given for solid deposits of material that build up on the surfaces of oil pipelines, pumps, reservoirs, and valves. It is caused by the build-up of calcium carbonate particles (causing limescale), iron sulfides, barium sulfates, strontium sulfates, and other particles carried along by the flow of oil.
Scale builds up inside oil systems and prevents oil from flowing through the system correctly. Flow assurance is a key economic and logistical factor in the oil and gas industries, and so different strategies are used to remove scale and prevent scale from building up in oil systems and blocking the oil’s smooth flow through them.
There are three main methods of dealing with scale:
- Sequestration of sulfate ions from sea injection waters
- Chemical scale dissolution or mechanical scale removal
- Application of scale inhibitor chemicals (SIs) to the oil to prevent scale from building up in the first place
While the other methods can be useful ways of dealing with a mild scale problem or performing a temporary fix, the application of SIs has been proven to be the most efficient and cost-effective method of preventing scale from negatively affecting flow assurance, and is widely used in the industry.
What are SIs?
SIs are chemicals produced for the specific purpose of delaying, reducing, or preventing scale deposition when added to oil production systems.
Polymers of acrylic acid and maleic acid, as well as phosphonates, have been used extensively as SIs. This is because of their good dosage efficiency, thermal stability, and excellent solubility.
Combined with other industrial chemicals added to oil systems – such as are frequently used in exploratory, drilling, well completion, and start-up operations – SIs in oil mean that produced fluids and waste can be harmful to the surrounding environment.
Parts of the industry have been making efforts since the late 1990s to ensure degradable and non-toxic SIs are used. However, these alternatives are often less efficient or more expensive than their more potentially harmful counterparts.
Next-Generation SI Analysis
SI analysis is used to evaluate the effectiveness of SIs in the oil system. There are a number of techniques currently in use to perform these measurements, although these tend to give limited information such as the total chemical content in the sample, or higher-level elemental analysis without detailed chemical speciation.
Chemical speciation refers to the distribution of a particular element among chemical species within a system. Analyzing this distribution is important for understanding chemical toxicity in samples and the transport and fate of chemicals through the surrounding environment.
Key to understanding the scale of potential environmental problems with SIs and other oil treatments – and remedying them – is a better understanding of the chemical speciation of treated oil as it flows through and out of the oil production system.
The increasingly widespread use of surface-enhanced Raman spectroscopy (SERS) in SI analysis is a welcome step forwards in this regard. The nanotechnology-based method can provide data on chemical speciation in samples through manipulation of the Raman effect.
Light is emitted to the sample, and the light that is reflected from the sample at different wavelengths is recorded. Each spectra – wavelength – that is recorded provides a unique “fingerprint” that can be used to accurately identify individual particles in the sample.
The distribution, location, over size, and other descriptions of the chemical in the sample can be determined through SERS, therefore enabling an SI analysis that provides the full picture for treated oil’s chemical make-up.
As well as this, the SERS method developed in the latest research – which also used handheld instruments for more versatile and dynamic applications – provided better detection and quantification of SIs than traditional SI analysis techniques, and did so faster and with less cost.
Nanotechnology to Minimize Environmental Destruction
Environmental destruction is arguably the key challenge facing humanity today. In every industry – especially those that share a greater degree of responsibility for this destruction – efforts must be made to reduce negative impacts on the environment as much as possible.
To do this effectively, a more accurate measurement of that impact is necessary. Nanotechnology-based approaches such as the SERS SI analysis discussed here will be increasingly sought after due to their potential for high degrees of accuracy and precision, cost-effectiveness, and efficiency.
References and Further Reading
Boak, S. and S. Sorbie (2010) New Developments in the Analysis of Scale Inhibitors. SPE Prod and Oper. SPE. https://doi.org/10.2118/130401-PA.
Laing, N., Graham, G. and J. Dyer (2003) Barium Sulphate Inhibition in Subsea Systems - The Impact of Cold Seabed Temperatures on the Performance of Generically Different Scale Inhibitor Species. Paper presented at the International Symposium on Oilfield Chemistry, Houston, Texas, February 2003. SPE. https://doi.org/10.2118/80229-MS.
Murugesan, S., Ahoor, D., Souza, L., Liu, Y., Heath, S. and B. Hughes (2020) Next Generation On-Site Scale Inhibitor Analysis – Surface Enhanced Nanotechnology Detection. Paper presented at the SPE International Oil Field and Scale Conference and Exhibition, online, June 2020. SPE. https://doi.org/10.2118/200702-MS
VanBriesen, J., Small, M., Weber, C. and J. WIlson, (2010) Modelling Chemical Speciation: Thermodynamics, Kinetics and Uncertainty.” Modelling of Pollutants in Complex Environmental Systems. CMU. [Online] https://www.cmu.edu/homepage/environment/2011/fall/chapter_04.pdf.
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