Oilfield metal naphthenate formation and mitigation measures: a review

Eke, William Iheanyi; Victor-Oji, C. O.; Akaranta, Onyewuchi

doi:10.1007/s13202-019-00797-0

Cited by 14 publications

(4 citation statements)

References 71 publications

(185 reference statements)

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“…In this paper, the pH of the water was decreased by the addition of hydrochloric, citric, acetic, and formic acids. Furthermore, LDNIs (lowdosage naphthenate inhibitors) were examined; these could act in conjunction with NAs to maintain the pH of water and combat naphthenate precipitation [8]. In Norway, these products have been successfully used in the Heidrun oilfield, where they are mixed with a demulsifier, as they were shown to be ineffective when used alone [9].…”

Section: Rcooh → Rcoomentioning

confidence: 99%

Prevention and Removal of Naphthenate Deposits in Oil and Gas Production—Historical Background and Novel Attitude towards Inhibition and Solution

Korzec,

Sapińska-Śliwa

2023

Energies

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The authors studied the problem of naphthenate deposits in the oil and gas industry. Currently, there are few ways available to inhibit or dissolve naphthenate deposits in oil facilities. Naphthenate deposits can block pipelines and aggregate in other parts of the installation, i.e., in the separators. In Europe, the issue of deposition on oil rigs is commonly encountered in Norway and the United Kingdom, as well as in some African countries, i.e., Angola and Nigeria. Many tons of chemicals are used to combat naphthenate deposition, usually through inhibition, but also via the dissolution of the scale that precipitates over time. The presented work examines the characteristics of naphthenate fouling, historical ways to inhibit it, and current approaches to the problem, as well as the results of the laboratory testing of naphthenate inhibitors and solvents. The process of the naphthenate creation is as follows. When oil exhibits a high TAN (total acid number) and high content of salty water, naphthenate deposits can emerge via the reaction of naphthenic acids and metal salts (mostly calcium ones). Naphthenates are partially insoluble in water, and they usually float below the oil/water interface. The standard methods of naphthenate inhibition involve lowering the pH of the production water, which can result in serious problems, especially related to corrosion. This study addresses experiments conducted in the laboratory in Poland and on oil rigs in Angola and is based on contemporary knowledge and standards. The objective of this paper was to investigate the most suitable naphthenate inhibitors and solvents, as well as to undertake bottle tests of naphthenate inhibitors with a focus on the main indicators (water clarity, quality of separation surface, and clarity of oil). The use of citric and formic acids in this paper is a novelty, and it is compared with the results obtained with the more commonly used acetic acid, hydrochloric acid, and ABS acid. It was proven that formic acid can effectively inhibit and dissolve naphthenic deposits (99% efficiency of inhibition and 100% efficiency of dissolution). It was found that some acids used in naphthenate inhibition create more deposits than were originally present. Formic acid and ABS acid yielded significantly better results than other types. It is also here hypothesized that there are substances other than acids that can effectively remove naphthenate deposits, and the other novelty of this study is in the use of mutual solvents in the removal of naphthenate salts. Another important outcome is the finding that not only acids but also mutual solvents (EGMBE and isopropyl alcohol) can effectively remove naphthenate deposits. The test results show that formic acid dissolved all of the naphthenates, while citric acid had 97% efficacy, isopropyl alcohol had 95% efficacy, and EGMBE showed 94% efficacy. The impacts of commercial naphthenate inhibitors on the bottle test results and interfacial tension measurements were also investigated. It was shown that commercial naphthenate inhibitors can decrease the interfacial tension between oil and water by more than 30% when used at dosages of 400 ppm.

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Section: Rcooh → Rcoomentioning

confidence: 99%

Prevention and Removal of Naphthenate Deposits in Oil and Gas Production—Historical Background and Novel Attitude towards Inhibition and Solution

Korzec,

Sapińska-Śliwa

2023

Energies

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“…In the process of oil processing and production, scaling or sedimentation is easy to occur in the pump and electric desalting device. , According to the chemical composition, the sedimentation can be divided into wax deposition, asphaltene deposition, and naphthenic acid deposition, in which naphthenic acid deposition is the most common sedimentation for offshore oilfield exploitation and processing in recent years. Naphthenate deposition in crude oil processing has been a well-recognized problem that has grown significantly in the past two decades, which have been reported in some offshore oil fields such as North Sea, Nigerian, Heidrun, Southeast Asia, as well as West Africa …”

Section: Introductionmentioning

confidence: 99%

“…The formation of naphthenate deposit depends mainly on the presence of a specific group of large molecular weight naphthenic acids, namely, ARN. − The molecular composition of ARN has been characterized by high-resolution mass spectrometry. ,,,, ARN is a kind of naphthenic acid with a special structure, which corresponds to a group of tetrameric acids with 4–6 naphthenic rings. ARN has a carbon number range around C 60 -C 86 , in which C 80 is dominant in all samples. , ARN occurs in a concentration range of 0.6–3.6 ppm in the limited number of investigated crude oils but is predominant in calcium naphthenate deposits. ,,, It is believed that the presence of ARN can be a potential indicator of calcium naphthenate deposition, even if it is present in very low concentrations . Therefore, the ARN must be considered for the effective prevention of naphthenate deposition …”

Section: Introductionmentioning

confidence: 99%

Molecular Characterization of Naphthenic Acids and Naphthenates in the Oil Sludge: A Case Study in Bohai Basin, China

Han

et al. 2022

Energy Fuels

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Oil sludge deposition is a common phenomenon during oil transportation, storage, and processing. Detailed molecular characterization of sludges is a prerequisite for understanding the mechanisms of emulsification, naphthenate, and asphaltene deposition. In this study, naphthenic acids and their salts in the oil sludge from an offshore oil platform were characterized by negative ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry and hightemperature chromatography (HTGC). The results show that the oil sludge is a stable emulsion consisting mainly of water and crude oil. An insoluble fraction, which accounted for roughly 3 wt % of the sludge, was found containing a large amount Ca and Fe. The organic matter in solid was extracted by toluene/formate acid extraction and was identified as large-molecular binary, ternary, and quarternary naphthenic acids, including the C80 tetraacids (socalled "ARN"). HTGC results showed that the ARN accounted for more than half of the polybasic acids. It was considered that the Ca 2+ in the formation water and large molecular polyacids in the crude oil is the key factor for the sludge formation; small molecular naphthenic acids and other polar components in the crude oil stabilize the emulsion of the sludge.

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“…ARN tetrameric acid is responsible for the formation of calcium naphthenate deposit, , a major threat in crude oil processing. ARN is a family of cycloaliphatic compounds composed of 80 carbon atoms organized as four side chains with carboxylic acid functions at each of their four tips. − Their structure is very different from other naphthenic acids present in crude oils, which are predominantly monoacids. − Since its discovery in 2004 , and the recognition that its presence is a prerequisite for calcium naphthenate deposition, ARN tetrameric acid has been the subject of various research works that can roughly be classified into two categories:…”

Section: Introductionmentioning

confidence: 99%

Screening of Inhibition of Calcium Naphthenate Deposition in Crude Oil

et al. 2021

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One of the initial steps in calcium naphthenate deposition is the reaction between ARN and Ca 2+ leading to the formation of an interfacial gel. After growing, this gel will form calcium naphthenate deposits that are a threat for irregularities in crude oil production and processing. It has been previously shown that crude oil components such as asphaltenes and naphthenic acids can weaken and inhibit the formation of the interfacial gel. Based on this observation, the inhibition efficiency of four crude oils is compared. The variations of interfacial tension (IFT) and interfacial dilational modulus E′ of ARN solution (concentration = 10 μM) in contact with Ca 2+ -containing aqueous solution (pH = 8) with varying crude oil concentration allow us to define a parameter characterizing the interfacial gel inhibition efficiency of crude oils to compare the systems with each other. The determined inhibition efficiency order of crude oils is not directly related to the total asphaltene and naphthenic acid contents in the crude oils and, therefore, cannot be directly predicted by performing simple chemical analysis of the oils. By selectively removing asphaltenes and/or naphthenic acids, it was found that naphthenic acids are the most prevalent inhibitors followed by asphaltenes in the tested crude oils. Other compounds present in crude oil also have a weak inhibition activity on the ARN/Ca 2+ interfacial gel. Finally, bottle tests were performed to upscale the results obtained at the interfacial scale. Bottle tests were performed at an ARN concentration 10 times higher than that used for IFT and interfacial rheology measurements. The tests indicate the presence of a soft solid material formed by the reaction between ARN and Ca 2+ even in the presence of the crude oil that was found to have the highest interfacial gel inhibition efficiency. This apparent contradiction is not understood at the moment, and hence, a better understanding of the ARN/ Ca 2+ system is required to extrapolate the results obtained at the interface to bigger scales.

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Oilfield metal naphthenate formation and mitigation measures: a review

Cited by 14 publications

References 71 publications

Prevention and Removal of Naphthenate Deposits in Oil and Gas Production—Historical Background and Novel Attitude towards Inhibition and Solution

Prevention and Removal of Naphthenate Deposits in Oil and Gas Production—Historical Background and Novel Attitude towards Inhibition and Solution

Molecular Characterization of Naphthenic Acids and Naphthenates in the Oil Sludge: A Case Study in Bohai Basin, China

Screening of Inhibition of Calcium Naphthenate Deposition in Crude Oil

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