Several studies aimed at understanding and combating scale formation in the oil and gas industry have
been mainly carried out in single phase brine solution, however, for chemical inhibitors to be effectively
deployed to mitigate scaling, it is essential to develop an experimental matrix and laboratory tests to
assess its effectiveness in the presence of multiphase fluids. The objective of this study is to evaluate
the impact of various organic phases in produced fluids on the inhibition efficiency of
polyphosphinocarboxylic acid (PPCA) on calcium carbonate scale precipitation.

Single and multiphase tests were conducted for CaCO3 precipitation at 30°C. The mixture of CaCO3 brine
(SR 211) and oil fractions was continuously stirred with an overhead impeller blade at 520 rpm to create
homogeneous dispersion. The oil fractions include 50ml cyclohexane, 30ml kerosene, 20ml toluene and
0.01% asphaltene, fully dispersed in toluene. The substrate (RCE sample) on which surface deposition
was assessed is a cylindrical piece of stainless steel (SS 316L) mounted on a shaft rotated at 400rpm by
the overhead stirrer. The impact of the multiphase fluids on chemical scale inhibition was investigated
with PPCA inhibitors at minimum inhibitor concentration (MIC) determined from the single phase. Bulk
samples were taken at different time intervals and analysed by SEM, AAS and XRD to evaluate the
precipitation process, size, morphology and kinetics of transformation.

The results show an increase in the deposition for the oil-water system containing various organic
phases. Under the same condition and duration of test, the MIC required to prevent scale formation in
the bulk was shown to vary between the oil-free and the different oil-water systems. These results helps
to improve on current understanding of calcium carbonate polymorphs crystallization in the presence of
inhibitors.