erosion of material used in petroleum production

Prévia do material em texto

ELSEVIER Wear186187 (1995)493496 
WEAR 
Erosion of material used in petroleum production 
R. Hamzah, D.J. Stephenson *, J.E. Strutt 
School of Industrial and Manufacturing Science, Cranjeld University, Cranjield, Bedford MK43 OAL, UK 
Abstract 
Erosion<orrosion arising from sand production is increasingly recognised as a significant problem in petroleum production. When erosion 
and corrosion interact, they do so in such a complex manner that it is difficult to determine the rate of metal loss with sufficient accuracy for 
reliable prediction of equipment lifetimes. 
An experimental programme was carried out to study the interaction between the erosion and corrosion under typical petroleum production 
conditions. A C-Mn steel has been exposed to environments simulating wet and dry CO2 conditions. Erosion has been simulated by the 
introduction of sand particles (50-300 /.m) and the influence of impact angle, velocity, particle loading and temperature has been investigated. 
The results demonstrated that for C-Mn steels there is a significant interaction between erosion and corrosion with the rate of metal loss 
from pure corrosion to erosion/corrosion increasing by 2 orders of magnitude. The use of wet CO* increases the rate of metal loss by factor 
of 2-4. It has been shown that the metal recession rate at low velocity is dominated by the formation and removal of surface corrosion 
products. 
Keywords: Petroleum production; Erosion; Corrosion; Sand 
1. Introduction 
Erosion+orrosion arising from sand production is increas- 
ingly recognised as a significant cause of equipment failure 
in petroleum production. It is believed that the combined 
results of erosion and corrosion would increase rates of metal 
loss. Typical examples of equipment failures such as the 
permanent choke and the blast joint of the production tubing 
shown in Fig. 1 are common forms of failure [ 11. 
From the experience of petroleum production in Malaysia 
and other parts of the world, the implementation of sand 
production controls, such as gravel-packing completions, and 
prone reservoirs may still produce sand up to 5 pounds per 
thousand barrels (pptb) [ 2,3]. This is equivalent to sand flux 
rates of 0.01 g mm-* h-’ in 1 in tubing (see Fig. 2) [ I]. 
With the introduction of a threshold limit of safe sand pro- 
duction of between 10 and 20 pptb. (0.1-0.2 g mm-* h- ’ 
for 2 in tubing and >0.5 g mm-* h-’ for 1 in tubing) by 
some companies, considerable metal loss rates may take place 
which may render the previously assumed safe practice as 
unsafe. 
2. Experimental 
A series of experiments was conducted to determine the 
rates of corrosion, erosion and erosion-corrosion in dry and 
* Corresponding author. 
Elsevier Science S.A. 
SSDIOO43-1648(95)07127-X 
wet CO, environments on typical steels used in petroleum 
production. The autoclave shown in Fig. 3 and centrifugal 
erosion rig shown in Fig. 4 were used for the tests [ I]. 
A wet CO2 environment was introduced by feeding water 
and CO, gas into the test chamber and using an ultrasonic 
atomizer to simulate a wet gaseous environment. Mains water 
was used which contained typically 5 ppm oxygen. However, 
by forming an ultrafine mist of water droplets, rapid equili- 
bration with the CO, environment ensured that the activity 
of oxygen in the water on the surface of specimens was 
extremely low. This was confirmed by the corrosion scales 
which were greyish black, typical of ferrous carbonate films. 
Fig. 1. Erosion/corrosion in oilfields: (a) permanent choke; (b) production 
tubing. 
494 R. Hamzah et al. /Wear 186-187 (1995) 493-496 
g/mm_2/h. 
l.OE+OZ E 
l.OE-03 --- li_-_-~ii 
1 10 100 1000 10000 
LB./lOOOEBL(~~tb). 
_.._ 
+ 1’ Tubing -+ 2’ TubinQ -se 3’ Tubing 9 4’ Tubing 
Fig. 2. Sand flux rates conversion. 
F”,“.C, _ ??
??
i 
. 
L.“., d bP.c,m.n 
??
??
Fig. 3. The autoclave for corrosion test. 
Fig. 4. The centrifugal erosion-corrosion test rig 
Tests were conducted at 20 and 80 “C with a positive pres- 
sure inside the chamber of approximately 0.5 bar(g) 
achieved by controlling a regulator valve from a gas bottle 
supplying 99.95% purity CO, gas. 
Tests were carried out with exposure times of between 5 
and 30 h, flux rates of 0.5, 0.1, 0.05 and 0.01 g mm-’ h- ’ 
and particles velocities of 20, 50, 80 and 150 m s ~ i 
The specimens were arranged such that the rates of metal 
loss at 15”, 30”, 45”, 60” and 90” impact angles could be 
calculated. The rates of metal loss for these tests were esti- 
mated by the weight loss method. 
3. Results and discussion 
Typical erosion and erosion-corrosion rates vs. impact 
angle, as shown in Figs. 5 and 6, were obtained from the tests 
[ 11. It is clearly shown that the presence of the corrosive 
environment (Fig. 6) increases the rate of purely erosive 
metal loss (Fig. 5) by a factor of 2-4. 
As expected, the rate of metal loss increases with increas- 
ing sand flux rate. The value of velocity exponent obtained 
from the experiments was found to be between 2.5 and 2.9 
in agreement with values obtained by previous workers [4- 
61. 
For carbon manganese steels, at low velocities 
( < 50 m SK’), the erosion mechanism is essentially domi- 
nated by scale formation and removal. However, as the veloc- 
ity of particles increases beyond 50 m s- ’ at sand flux rates 
above 0.5 g mm-’ h-i, the erosion process becomes domi- 
nated by substrate erosion. 
Wet CO, corrosion is generally regarded as film free at 
temperatures below about 40-60 “C. However, the erosion 
results indicate that the corrosion products do form even at 
20 “C. The corrosion products believed to form in wet CO, 
between 20 and 80 “C are those of ferrous bicarbonate and 
ferrous carbonate [ 7-91. At these temperatures, they are soft 
in nature and loosely adherent to the surface. 
Corrosion rates are greatly reduced by the presence of a 
scale as ferrous ion concentrations reach their saturation level 
beneath the bicarbonate or carbonate layer [ 10,111, effec- 
tively polarising the anodic dissolution process. However, 
when sand particles impact the surface, the growing scale is 
removed locally depolarising the anodic sites and accelerat- 
ing the corrosion rate. This process is repeated for every 
particle impact on the surface. 
It has been found that the difference between the wet and 
dry erosion rates for X52 greatly exceed the rate of CO, 
corrosion as measured by conventional corrosion tests, indi- 
cating that there is a strong synergism between the erosion 
and corrosion processes. 
4. Conclusion 
The following conclusions have been drawn from the 
experiments related to sand erosion corrosion of oilfield mate- 
rials and environments. 
R. Hamzah et al. /Wear 186-187 (1995) 493-496 495 
1. 
2. 
3. 
4. 
/A _f_P---- 
,.OE-01 
i /-- 
___.___-. .__ 
-+_-_ 
I.OE-02 F 
,.OE-03 II:lli 
16 30 46 60 75 90 0 15 30 46 80 76 90 0 
lmpol An9l.4, 9s.a. 
r----- --- 
Dw Atmos..Flux’O.O~/mm2/~T’2OC.X52 Dry Almo~..Vp-Wml9,T-ZOC.X52 
Fig. 5. Erosion rates for X52. 
Flux. ghnm-2lh 
- 0.60 4 0.10 A+ 0.06 --g 0.0, 
(b) 
Fig. 6. Erosion-corrosion rates for X52 
- ATTy.?OC -s co2.2oc ff co2.aoc 
-__ J 
OIAtm..W*t CO2 . ZOCIBOC.“9-~Omls.F.0.06 
When sand is produced the rates of metal loss are greatly 
accelerated. 
The rate of corrosion itself is accelerated beyond that 
expected for the process fluid conditions as fresh metal 
surface is continually exposed to the corrosive environ- 
ment due to repeated impact by sand particles. 
The particles do not need to acquire high kinetic energy 
or velocity in order to remove the soft corrosion products 
as encountered in a sweet corrosion situation. 
At high velocity, > 50 m s- ‘, mechanical erosion of the 
substrate is the predominantprocess and velocity expo- 
nents in the range 2.5-2.9 have been measured. 
Acknowledgements 
The authors wish to thank PETRONAS, The Malaysian 
National Oil Company for the financial support of the project, 
PETRONAS Carigali Sdn. Bhd./Baram Delta Operations for 
making their resources available in obtaining the field data. 
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