Classification: Internal
Status: Draft
Evaluation of Gjøa Project – why not PWRI?
environmental aspects
Olav Dolonen, Gaz de France, Norway
Produced Water Management 2008
22 - 23 January 2008, Stavanger, Norway
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What is the Gjøa platform named after?
•
“Gjøa” is the vessel the explorer Roald Amundsen selected for his voyage through the
Northwest passage. It was the first vessel in the world to transit Northwest Passage.
•
"Gjøa" is a 47 ton, 70 foot sloop built in Rosendal, Norway, in 1872. Was named Gjøa
after the name of the first owners wife. Used a fishing vessel until Amundsen bought it
•
P. Ristvedt, G. Hansen, A. Lindstrøm, R. Amundsen, A. Lund, H. Hanssen and G. Wiik
on board Gjøa. Set out from Christiania (now Oslo) in June 1903
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Gjøa history
• The course was set for the Labrador
Sea west of Greenland
• In October they were in King William
Island, where they was iced in. They
stayed in the ice for nearly two years
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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The Gjøa field
Gjøa
Vega
Camilla&Belinda
Gjøa
Tampen
History
•
•
•
Discovered by operator Hydro in 1989
Gaz de France acquired a 30% interest from
Hydro in 2003 and became the operator
The field is being developed via a joint operator
ship between Gaz de France and StatoilHydro.
Kvitebjørn
Valemon
StatoilHydro is operator during the development
phase, whilst Gaz de France will take over at
start of production in October 2010.
Huldra
Troll
Hild
Oseberg
Oseberg
Troll
License
•
•
•
•
•
Olav Dolonen, Produced Water Management Conference, 23.01.2008
StatoilHydro
(Development operator)
Gaz de France
(Operations operator)
20 %
30 %
Petoro
30 %
Shell
12 %
RWE Dea
8%
5
Gjøa platform with tie-ins
Vega
Oil export
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Olav Dolonen, Produced Water Management Conference, 23.01.2008
•
•
•
•
Topside dry weight
20 000 tonnes
Topside size
110 x 85
Displacement
59 000 tonnes
LQ capacity
(with 20 turn able beds)
100
cabins
•
•
•
Oil export capacity
13.8
kSm3/d
Gas export capacity
17
MSm3/d
No drilling rig onboard
m
7
Produced water profile for Gjøa
16000
15.000 m³/d produced water design capacity
14000
12000
10000
8000
6000
4000
2000
0
2010
2012
2014
2016
2018
Olav Dolonen, Produced Water Management Conference, 23.01.2008
2020
2022
2024
2026
2028
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Produced water capacities
• Gjøa installation has the following produced water requirements;
– Gjøa
Design capacity 15.000 m³/d (625 m³/h)
– Vega tie-in
Design capacity 10 m³/d. Will be solved in the MEG used for
hydrate inhibition, i.e. no need for produced water treatment
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Produced water requirements from the authorities
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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The environmental challenge for Gjøa
•
The environmental challenge
– The main environmental challenge of Gjøa is to achieve an optimal resource
development and at the same time minimise the produced water production, energy
consumption and use of chemicals. Firm restrictions are therefore established in the
project to minimise the total environmental risk as low as possible within frames put
by BAT, safety, economy and other project relevant aspects.
•
Potential solutions for treatment of produced water at Gjøa
– The evaluated alternatives included
• control and potential limit of water production by well management
• reinjection
– for pressure support and contribution to increased oil production
– in water disposal wells (depositing produced water in a low pressure sand,
i.e. Utsira)
• efficient cleaning of produced water before discharge to sea
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Limit water production by well management
• Control and potential limit of water production by well management
– Well management is performed with downhole devices that can be
monitored and operated from surface, without having to perform a well
intervention. Its a valve system that regulates flow through it by either
hydraulic or electrical commands from an operator who makes the decision
to perform a certain action to improve flow or injection. And if there are
downhole sensors also implemented, these are also part of the active
completion system.
– Well management for Gjøa would mean the use of DIACS (Downhole
Instrumentation And Control Systems )
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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DIACS
• Conclusion
– StatoilHydro Gjøa reservoir group could not find sufficient reasons to install
DIACS. Based on simulations, any attempts of “steering” the wells would
result in shorter plateau (due to pressure loss) and thereby lost reserves.
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Reinjection
• Total environmental impact
– The total environmental impact from the alternative solutions for produced
water treatment will differ due to varying consequences wrt emissions to air
and discharges to sea. The evaluation of environmental impact to sea was
provided by calculation of an EIF. The environmental contribution for the
impact to air (CO2, NOx and VOC emissions) was estimated separately.
• Environmental Impact Factor (EIF)
– EIF - environmental index quantifying the risk of environmental damage of
produced water discharges. The EIF is based on a combined
environmental risk and hazard assessment, accounting for the composition
and amount of the produced water discharge togheter with possible
chemicals.
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Reinjection, total EIF (incl chemicals)
Gjøa Total EIF
250
238
200
Base case
EIF
150
133
Epcon CFU's
120
Epcon CFU's + Ctour
100
Base case + injection
50
5
0
Note: Small difference in EIF between Epcon and Epcon plus C’-Tour. Even though the
contribution of naphthalene, phenols and aliphates will be reduced by the use of C’-Tour,
the increase in BTEX result in that the EIF value will not be reduced. Actually, the value will
be higher, but this is within the uncertainty of the model
Source: Gjøa summary EIF
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Reinjection, environmental impact from CO2
CO2 emissions PWT VS PWI - 7a1
350000
GJØA T ot al PWT
300000
GJØA T ot al P WI
Tonn CO2
250000
200000
150000
100000
50000
0
2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Comparison emission profiles PWT vs PWRI : This results show that the CO2 per boe
during production increases with 15 % for the PWRI alternative
Note; These calculations are based on electrical power generated from fossil fuel
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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PFD of proposed PWRI
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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The Gjøa Reservoir
• Mainly shallow marine deposits
• Reservoir quality varies from poor to very good; layers of sand and silt inter
bedded with shale. Permeability varies.
• Thin oil column (32-45 m) with an overlaying gas cap
• Rotated fault blocks with high dip
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Considerations related to reinjection (1)
•
A concept based on produced water reinjection in the Gjøa area has the following
consequences:
–
Reinjecting into reservoir will for almost all cases increase water production and
thereby reduce the production, which ultimately results in lower recoverable
reserves. Injected gas and/or water will cone into the oil zone.
–
No shallow reservoirs for water disposal purposes exist in the vicinity of Gjøa
•
Results from reservoir knowledge and simulations based on new models
revealed that the Utsira formation (or other “sands”) is not present at the
Gjøa field
–
Reinjection gives increased energy consumption with ~5 MW. This gives an
increased emissions of C02 to air if power from shore is generated from fossil fuel
(Gjøa is planned to receive electrical power from the new power plant at
Mongstad)
–
A regularity of 90 % is assumed for the PWRI. The remaining 10% must at least
be treated to authority level of 30 mg/l before discharge to sea. This means that
Gjøa should be designed with nearly full scale produced water cleaning facilities
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Considerations related to reinjection (2)
– Reinjection require significant hardware, drilling operations and marine
operations; i.e. negative HSE and cost implications
– Considerable costs involved in the mitigating measures by PWRI to bring
the EIF number down from 120 to 5; MNOK/ ∆EIF = 13
• Conclusion
– The PWRI solution is out of the reference level and is rejected
OLF/ StatoilHydro: A reference level of 0.2 MNOK/ ∆EIF against which the cost-benefit ratio
for the additional mitigating actions is measured. In this case the ratio is far above
∆MNOK/ ∆EIF= 13 >> 0.2
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Preferred produced water solution
•
Produced water will be discharged to sea
–
The separation of oil from the produced water will be done by using
•
VIEC (Vessel Internal Electrostatic Coalescer) installed in 2nd stage
separator
•
Hydrocyclones cleaning the produced water from 2nd stage separator
•
EPCON technology for produced water from 3rd stage separator
•
EPCON technology downstream of the degasser
–
5 - 15 mg/l oil in water is expected in the discharged produced water
–
Recovered oil is recycled into the crude oil stream
–
Possible installation of C-Tour at a later stage in Gjøa lifetime
–
Treatment of drain water with EPCON (instead of conventional centrifuges)
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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PFD of produced water system on Gjøa
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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Solution for sand handling on Gjøa
•
Sand jetting and sand cleaning package
– Gjøa
The jetting operation is performed by closed loop circulation of produced water from
the degasser through the separator jet water nozzles, via a sand cyclone where the
sand is separated from the jet water. The jet water is then routed on to the
degasser.
– Vega
The jetting operation is performed by closed loop circulation of MEG from the rich
MEG tanks through the separator jet water nozzles, via a sand cyclone where the
sand is separated from the jet MEG. The jet MEG is then routed on to the MEG
degasser.
•
When the jetting operation is finished, the sand will be cleaned with produced water to
meet government requirements, before discharged overboard.
Olav Dolonen, Produced Water Management Conference, 23.01.2008
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PFD of sand cleaning system
Sand / liquid slurries
Vega
wellstream
Sand / liquid
cyclone
MEG for sand removal
Vega
1st stage
Accumulated
sand
Vega
2nd stage
Gjøa
gas
Gjøa
oil
Package
cirkulation
pump
Sand wash
package
Prod water for sand removal
Gjøa
1st stage
Gjøa
2nd stage
Disposal
to sea
MEG
degasser
Gjøa
3rd stage
MEG
jetting
pump
Prod water
jetting
pump
Olav Dolonen, Produced Water Management Conference, 23.01.2008
Skimming
to reject
system
Rich
MEG
tank
Gjøa
degasser
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Thank you for your attention
Thank you for your attention
Olav Dolonen, Produced Water Management Conference, 23.01.2008