Produced Water Cleaning and Re-Injection Experience - Zero Discharge to Water Michael Zettlitzer and Matthias Busch Wietze E&P Laboratory RWE Dea Germany RWE Dea 4th International Conference on Produced Water Management Stavanger, 31.01. to 01.02.2007
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Produced Water Cleaning and Re-InjectionExperience - Zero Discharge to Water
Michael Zettlitzer and Matthias Busch
Wietze E&P Laboratory
RWE Dea Germany
RWE Dea
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
2
Outline
� Introduction
� Concept of Water Treatment and Injection
� Water Treatment in RWE Dea’s North German Oilfields
� Long-term Water Injection Profiles
� Conclusions
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
3
Introduction
� RWE Dea founded in 1899
� Water injection since at least 1956, produced water re-injection since at least 1962, including pH-reduction with HCl
� Injection always below frac pressure according to German mining law
Matrix injection
� High-quality water treatment
� Formation water disposal
– disposal into the sea prohibited offshore Germany
– salinity constraints onshore for surface disposal
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
4
Goals of water treatment
� Long-term injection at low and preferably constant wellhead pressure
� Constraints:
– residual oil
– solids (incl. Fe-compounds)
– bacteria
– scale formation
– oxygen (?)
– clay swelling (?)
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
5
Significance of oil removal
� 40 ppm crude in injection water ~ 40 Liter crude/1000 m³
h = 10 m
r = 1 m
Porosity = 20 %
Pore volume = 6.3 m³
157 days of injection ~ 6.3 m³ crude
1000 m³ water/d40 ppm crude
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
6
0.0
0.1
0.2
0.3
0.4
0.5
0 20 40 60 80 100
Water saturation [% pore volume]
Re
lati
ve
pe
rmeab
ilit
y
020406080100
Oil saturation [% pore volume]
0.6
0.7
0.8
0.9
1.0
SorSwi
Effect of oil saturation on relative permeability for water – Water-wet rock
ko
kw(extrapolated)
ko(extrapolated)
kw
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
7
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 20 40 60 80 100
Water saturation [% pore volume]
Re
lati
ve
pe
rmeab
ilit
y
020406080
Oil saturation [% pore volume]
Swi Sor
1.0
100
Effect of oil saturation on relative permeability for water – Oil-wet rock
kw(extrapolated)
ko
ko(extrapolated)
kw
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
8
Effect of solids on injectivity(taken from Pang/Sharma, „A Model for Predicting Injectivity
Decline in Water-Injection Wells“ SPEFE, Sept. 1997)
Internal Filter CakeExternal Filter Cake
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
9
Injectivity decline caused by solids(taken from Pang/Sharma, „A Model for Predicting Injectivity
Decline in Water-Injection Wells“ SPEFE, Sept. 1997)
1Type Curve 1
Invers
eo
f In
jecti
vit
y D
ecli
ne
Pore Volumes Injected
1
Type Curve 2
Invers
eo
f In
jecti
vit
y D
ecli
ne
Pore Volumes Injected
1Type Curve 3
Invers
eo
f In
jecti
vit
y D
ecli
ne
Pore Volumes Injected
1
Type Curve 4(S Shaped)
Invers
eo
f In
jecti
vit
y D
ecli
ne
Pore Volumes Injected
external filter cake
internal filter cake
organic deposits
mixed effects
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
10
0
200
400
600
800
1000
1200
1400
0 20 40 60 80 100 120
Injected volume [pore volumes]
Flo
w r
ate
/dif
f. p
ress
. [c
m³/
(h·b
ar)
]
Constantflow rate(without solids)
Flooding with 10 ppm solids
Core flood test with crude-free brine containing solids, kinit.= 470 md, 105 g/l TDS
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
11
Bacterial activity (SRB)
� Severe mainly
– in low-salinity brine
– at low to moderate temperature
� Regular injection of biocides
– intermittent use of different biocides
– batch treatments with higher concentrations
� Regular checks of total count of bacteria and sulphate reducing bacteria (SRB)
� Regular determination of hydrogen sulphide content in associated gas
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
12
Adverse effects caused by bacteria
� Plugging of filters
� Formation of slimes in injection wells
� Increased risk of pitting corrosion
� Formation of hydrogen sulphide
– HSE aspects
– Risk of FeS-formation
– Stabilisation of emulsions
– Potential removal of hydrogen sulphide from sales gas
4th International Conference on Produced Water Management