Download - Zet t Litzer
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
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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
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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
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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
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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
Stavanger, 31.01. to 01.02.2007
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Facilities considerations from a company view
� Low operating cost (chemical dosage, filter replacement, disposal of sludges, …)
� Fully automatic water treatment desired
� Space and weight limitations offshore
� Cost of facilities as low as possible but as high as necessary
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
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crude
H2O
Demulsifier
ThreePhaseSeparator
Crude Separationand Storage
Pump SupplyTank
BoosterPump
Hydrocyclone
Walnut ShellFilter
Filter Bag(5 µm)
pH Adjustment
Biocide HCl
Injection Wells
Water treatment plant(German onshore and offshore field experience)
Gas
pH = 5
≈ 1 ppm crude
≈ 1 ppm solids
≈ 5 ppm crude
≈ 50 ppm crude
Production Wells
(Defoamer)
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
15
Improvement of water quality duringtreatment process
1. After FWKO
2. After Hydroclone
3. After Walnutshell-Filter
4. After Bagfilter at Wellhead
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
16
Produced Water Quality at Injection Wellhead vs. time
1
0.4
1 1
0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Res
idu
al o
il, so
lid
s [
mg
/l]
2
0.5
1
0.4
1
0.5
1
0.6
Feb 02 Mar 2002 Jul 03 Sep 04 Mai 05 Aug 05 Oct 06
Residual oil [mg/l] Solids [mg/l]
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
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Crude / water properties andtreatment capacity(German onshore/offshore field experience continued)
System temperatureCrude viscosity (50 °C)Crude densityWater density
Treatment capacity
::::
50 °C20 to 200 mPa·s920 kg/m³ (~19 to 22 °API)1150 kg/m³
2.5 x 106 t/year (~ 51,800 bbl/d)2.0 x 106 t/year (~ 36,200 bbl/d)
- crude- produced water
::
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
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0
500
1000
1500
2000
2500
3000
Nov-01
Feb-02M
ay-02Sep-02Dec-02
Mar-03
Jun-03
Oct-03
Jan-04
Apr-04
Aug-04Nov-04
Inje
cti
on
ra
te [
m³/
d]
0
25
50
75
100
125
150
We
llh
ea
dp
res
su
re[b
ar]
Formation: Dogger Sandstone Eff. Permeabilityw: 1178 md Perf. interval: 42 m
Injection profile H1 well
additional perforation
Injection rate
Wellheadpressure
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
19
crude
H2O
Demulsifier
ThreePhaseSeparator
Crude Separationand Storage
Pump SupplyTank
BoosterPump
GravelFilter
pH Adjustment
Biocide
HCl
Injection Wells
Water treatment plant (Germany onshore:
Hankensbuettel)
Gas
pH = 5
≈ 1 ppm crude≈ 1 ppm solids
< 20 ppm crude
Production Wells
AnnulusScale
Inhibition
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
20
Crude / water properties andtreatment capacity (Hankensbuettel)
System temperatureCrude viscosity (40 °C)Crude densityWater density
Treatment capacity
::::
40 °C8 to 20 mPa·s880 kg/m³ (~ 27-35 °API)1040 kg/m³
1.65 x 106 t/year (~ 30,000 bbl/d)formation water :
18,000 bbl/d600 bbl/d
Current water productionCurrent oil production
::
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
21
Injection profileHankensbuettel-Sued 3
Formation: Dogger Sandstone Permeability: 800 md Perf. interval: 22 m
0
100
200
300
400
500
600
Jul-86
Apr-89
Dec-91
Sep-94
Jun-97
Mar-00
Dec-02
Sep-05
Inje
cti
on
rate
[m
³/d
]
0
25
50
75
100
125
150
Wellh
ead
pre
ssu
re[b
ar]
Injection rate
Wellheadpressure
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
22
Produced water treatment and/or „polishing“Further field experience
� EPCON with and without flocculant
� Active charcoal
� OILSORB (organoclay)
462810141419BTEX03.03.2005
12:00
7859139266428644OIW03.03.2005
12:00
925295571113Alkanes03.03.2005
10:30
CFU+FU
CFU1+2
CFU+FU
CFU1+2
CFU1In
% removalConcentration (mg/l)Analytical parameter
Date & time
4th International Conference on Produced Water Management
Stavanger, 31.01. to 01.02.2007
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Conclusions
� Proper water treatment is a prerequisite for produced water re-injection into matrix.
� Water treatment includes
– removal of residual oil, solids (and oxygen)
– supervision of and countermeasures against bacteria
– addition of scale inhibitor, if necessary.
� pH-adjustment has a favourable effect on scale prevention and bacteria reduction in many field applications.
� After reservoir-adapted water treatment, continuous produced water re-injection with minor reductions in injectivity index is usually possible.