Abstract:
Experimental erosion/corrosion modelling was
performed on C-Mn steels and corrosion resistant alloys
commonly used in petroleum production. A graded commercial
sand of 50-30b pm size range, similar to sands produced from
typical oil/gas fields was used to simulate the erosive
medium. The experimental conditions such as the sand flux,
particle velocity, pressure and temperature, were chosen
based on typical field operating conditions for corrosion,
erosion and erosion-corrosion tests imposed on the materials.
The corrosion environment was created by feeding in CO2 gas
with atomised water into the test chamber. A centrifugal
erosion rig (45) with necessary modifications to suit wet and
dry test conditions was used in the experiments. The rig was
capable of generating over 150 m/s particle velocity and
could operate at high temperatures to generate consistent
results.
Results show that (a) there was a soft thin layer of
corrosion products formed on the C-Mn specimens even at 20°C
which can easily be removed by the impacting particles ,
(b)
the scale growth rate kinetics were found to be parabolic and
vary between 8x10-3 pun'/h to 50x10-3 iim2/h depending on the
material and temperature, (c) the process of metal recession
consists of the removal and regrowth of soft corrosion scale
at low flux and low velocity, and erosion of substrate at
high flux and high velocity, (d) the erosion-corrosion rates
were found to vary between 2- 30 times over the pure erosion
rates under the same conditions, depending on the sand flux,
particle velocity and temperature.
An existing computer simulation model (46) was used
to simulate the conditions observed from the experiments.
Some improvements were incorporated into the programme and
the final model is capable of predicting the erosion and
erosion-corrosion rates applicable to petroleum production.