ARN Acids

Naphthenate solids are naturally occurring oilfield fluid scales formed from reactions between a specific group of high molecular weight cyclic naphthenic ARN acids, also known as Tetra Protic Acids or Tetra-Acids, with dissolved divalent cations [such as Ca, Mg and Fe] that come from the associated produced water in some oilfields. These hard solids can restrict production and in extreme cases render control systems inoperable and shutdown production.


Sodium Carboxylate soaps are formed from shorter chain, carboxylic ARN acids, also known as Fatty acids. The soaps are responsible for stabilising emulsions which in turn can adversely impact oil dehydration, fluid desalting, produced water treatment and disposal, oil storage and export.


In collaboration with the University of Plymouth, C80-82:0-8 tetra protic acids present in a test fluid or solid sample can be extracted by sequential ion exchange solid phase extraction, as described by Sutton and Rowland [2014; Energy and Fuels, 28, 5657-5669 (DOI: 10.1021/ef5012337)], and semi-quantified using liquid chromatography coupled with heated electrospray ionisation/high resolution accurate mass spectrometry [LC/HESI/HRAM-MS].


The KAT / University of Plymouth partnership can also provide the distribution of the nC8-20 carboxylic acids [identified as their methyl esterified derivatives by HTGC].


If ARN acids present an issue with respect to solids deposition or emulsion stability, then precipitation bottle tests can be performed to assess water and oil interface layers for evidence of carboxylate soap formation or naphthenate precipitation. Similarly, the bottle tests can be used to screen potential chemical management solutions.