SPE Journal
Online First
Summary
In this paper, the use of a quartz crystal microbalance (QCM) with a quartz
crystal sensor coated with iron oxide is proposed to evaluate the efficacy of
inhibitors in the prevention of scale formation. The quartz crystal was first
iron-plated by electrodeposition over the original gold film on the outer side
of the crystal and then oxidized. The iron oxide layer is more representative
for an evaluation of the inhibitor's effectiveness because tubing and equipment
in oil-industry facilities are made of low carbon steel that is coated with an
iron oxide layer. The scale formation was conducted under a steady
supersaturation condition. The experiments were performed with slow addition
(0.2 cm3/min) of 40 cm3 of Na2CO3
solution (1,000 ppm) to 200 cm3 of synthetic formation water
(AF-W2). The performance at 10 ppm concentration of two commercial scale
inhibitors, diethylenetriamine penta(methylenephosphonic acid) (DETPMPA) and
polyphosphonocarboxylic acid (PPCA), was evaluated. The mass variation on the
iron-oxide-plated QCM crystal sensor, caused by CaCO3 deposition, is
related to supersaturation, pH value, and efficacy of scale inhibitor.
Scanning-electron-microscope (SEM) images show that besides calcite crystals,
there are also deposits in the form of spherical lenses, which is
characteristic of the polymorph vaterite.
© 2013. Society of Petroleum Engineers
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History
- Original manuscript received:
8 August 2012
- Revised manuscript received:
23 October 2012
- Manuscript approved:
31 October 2012
- Published online:
23 January 2013
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