Thermal in-situ methods for bitumen production Field Facilities Steam Assisted Gravity Drainage (SAGD) Cyclic Steam Stimulation (CSS) Steam Emulsion: Bitumen + Water Steam Chamber Steam Emulsion: Bitumen + Water Steaming Soaking Production Central Processing Facilities Field Facilities Oil Treating De‐oiling Water Treating: Lime Softening or Evaporation Steam Generation (OTSGs) Emulsion: Bitumen + Water Diluted bitumen to upgrader or sales Diluent Produced Water Deoiled Water BFW Steam Canada’s oil sands is the third largest proven crude oil reserve in the world, estimated at 171 billion barrels. About 80% is recoverable by in‐situ and the remaining 20% by surface mining methods. The main thermal in‐situ method is called steam assisted gravity drainage (SAGD) where bitumen is recovered using horizontal well pairs and steam stimulation. The key parameter of a SAGD project is the steam‐to‐oil ratio (SOR) which varies from 2 to 7 depending on the quality of the reservoir and life of the well pairs. Fossil fuels are burned to generate the required steam, which results in GHG emissions. From a well‐to‐wheels life cycle point of view, the GHG emissions for SAGD bitumen are 18% higher than Arab‐Medium crude oils. This paper summarizes the application of Pinch Analysis on the design and retrofit of SAGD plants. Key conclusions and recommendations are: The pinch point is caused by the hot emulsion (bitumen and produced water) coming from the well pads. Heat integration can be improved if the emulsion arrives at the central processing facility (CPF) hotter. This can be accomplished by using mechanical lift instead of gas lift so that the produced fluids don’t have to be flashed at the pad group separators. At the Nexen Long Lake facility the produced fluids from pads with no group separators reach the CPF at approximately 180°C instead of 161°C. Blowdown is the hottest stream (approx. 314°C in most SAGD plants). The trade‐off between water and energy conservation defines the use of this blowdown stream. At the Nexen Long Lake facility, blowdown is flashed in a two effect evaporation scheme to maximize water recovery. LP condensate is used in our bitumen upgrader which consumes considerable amounts of water due to the gasification process. Diluent, required for the oil‐water separation, should be pre‐heated before being mixed with hot emulsion, otherwise it is impossible to design a heat exchanger network that satisfies the energy targets. Most designers avoid pre‐heating make‐up water (brackish water) because of hardness scaling. Proper selection of the injection point can save both energy and capital. Glycol as heating and cooling media can be minimized resulting in savings of capital and energy. Studies have shown that the use of Pinch Analysis on the design and retrofit of a SAGD facility, as well as the switch from mechanical to gas lift, can result in energy savings close to 20%. Canada’s oil sands is the third largest proven crude oil reserve in the world, estimated at 171 billion barrels. About 80% is recoverable by in‐situ and the remaining 20% by surface mining methods. The main thermal in‐situ method is called steam assisted gravity drainage (SAGD) where bitumen is recovered using horizontal well pairs and steam stimulation. The key parameter of a SAGD project is the steam‐to‐oil ratio (SOR) which varies from 2 to 7 depending on the quality of the reservoir and life of the well pairs. Fossil fuels are burned to generate the required steam, which results in GHG emissions. From a well‐to‐wheels life cycle point of view, the GHG emissions for SAGD bitumen are 18% higher than Arab‐Medium crude oils. This paper summarizes the application of Pinch Analysis on the design and retrofit of SAGD plants. Key conclusions and recommendations are: The pinch point is caused by the hot emulsion (bitumen and produced water) coming from the well pads. Heat integration can be improved if the emulsion arrives at the central processing facility (CPF) hotter. This can be accomplished by using mechanical lift instead of gas lift so that the produced fluids don’t have to be flashed at the pad group separators. At the Nexen Long Lake facility the produced fluids from pads with no group separators reach the CPF at approximately 180°C instead of 161°C. Blowdown is the hottest stream (approx. 314°C in most SAGD plants). The trade‐off between water and energy conservation defines the use of this blowdown stream. At the Nexen Long Lake facility, blowdown is flashed in a two effect evaporation scheme to maximize water recovery. LP condensate is used in our bitumen upgrader which consumes considerable amounts of water due to the gasification process. Diluent, required for the oil‐water separation, should be pre‐heated before being mixed with hot emulsion, otherwise it is impossible to design a heat exchanger network that satisfies the energy targets. Most designers avoid pre‐heating make‐up water (brackish water) because of hardness scaling. Proper selection of the injection point can save both energy and capital. Glycol as heating and cooling media can be minimized resulting in savings of capital and energy. Studies have shown that the use of Pinch Analysis on the design and retrofit of a SAGD facility, as well as the switch from mechanical to gas lift, can result in energy savings close to 20%. Make-up Water Lime sludge or concentrate to disposal Blowdown (after treatment and/or partial recycle) to disposal Pinch Analysis of Central Processing Facilities SOR = 3.0; Warm Lime Softening/OTSG; Full Blowdown Recycle; T min = 10°C BFW/Wet Steam HP Blowdown Emulsion Make-up Water Dilbit & Water Disposal In most SAGD/CSS plants, the pinch point is located at the inlet temperature of the emulsion Moving the pinch point: impact of lift mechanism (Gas vs. Mechanical Lift) Emulsion to CPF Lift Gas, Flashed Steam, Produced Gas Casing Gas Production Group Separator ~ 700 kPa ~165°C 180-200°C Lift Gas Producer Emulsion to CPF Casing Gas to CPF (small volumes) Production 180-200°C Producer Gas Lift Mechanical Lift Electrical Submersible Pump (ESP) Natural Gas (and GHG) reduction can reach more than 10% Energy vs. Water Conservation CNOOC acquisition: On February 25, 2013, Nexen announced that CNOOC Limited has completed its acquisition of Nexen, which now becomes a wholly-owned subsidiary of CNOOC Ltd. As part of the agreement, Nexen will managed CNOOC Limited’s assets in North and Central America (slide above not updated to reflect this recent news). About Nexen Process Integration Applied to Thermal In-Situ Oil Sands Projects Denis Westphalen ([email protected]) Calgary, Alberta - Canada Development Engineer, Oil Sands Planning & Economics, Nexen Inc. If Lime Softening is used, TDS of Boiler Feed Water can be as high as 8,000 ppm which forces the use of Once Through Steam Generators (OTSGs) with steam qualities no higher than 80%. Steam is generated at high pressures (11 MPa) to save on steam lines to field facilities. HP Blowdown consists of a hot stream (~314°C) with high solids content (40,000 ppm TDS). Design for Energy Conservation Design for Water Conservation OTSG Steam 75-80% quality Steam to Field HP Blowdown ~314°C To Disposal Recycle OTSG Steam 75-80% quality HP Blowdown ~314°C Glycol cooling MP LP LP Blowdown to Disposal MP Condensate to Recycle LP Condensate to Recycle Steam to Field There are several other configurations for handling HP blowdown such as one flashing level (LP), mechanical vapor recompression (MVR) evaporation, hybrid (parallel flashing heat recovery), etc. The right configuration for a particular project is a choice between energy and water configuration and depends on Produced Water and Make-up Water qualities (TDS), water source type (fresh or brackish), Water Treatment Technology (Lime Softening or Evaporation), Disposal Methods, Project Specific Constraints and Regulatory Approvals. Natural Gas consumption may vary in more than 15% depending on the selected scheme. Typical Water Recycle Rate: 50 to 90% Typical Water Recycle Rate: >98% Do’s and Don’ts Boiler Feed Water Summary Diluent: Diluent (gas condensate, naphtha, synthetic crude oil) is mixed with the emulsion to promote the water-oil separation. In most designs, cold diluent (~15°C) is mixed directly with the partially cooled emulsion. This approach is justified because it eliminates one heat exchanger. If instead, diluent is pre-heated in a heat exchanger to ~125°C (oil treating temperature), 1-2% energy savings are obtained by a better heat exchanger network design. Make-up Water: Industry is being pushed to use more brackish water instead of fresh. Brackish water cannot be heated in a heat exchanger because of hardness precipitation. A common approach is to mix it cold with de- oiled water, which may result in additional steam consumption in a Hot Lime Softening system (any steam usage results in pinch crossing). If instead, brackish water is mixed with produced water (prior to de-oiling), no additional steam is required and savings on glycol cooling and heat exchanger size are obtained. Glycol: During final design stage, operations representatives push the excessive use of cold and hot glycol as heat transfer media, claiming better operability – which always result in higher CAPEX and OPEX. Dilbit 120°C Make-up Water 5°C 85°C 86°C 1 Heat Exchanger LMTD = 54.8°C Dilbit 120°C Make-up Water 5°C 85°C 86°C 2 Heat Exchangers LMTD = 25.8°C LMTD = 32.7°C C Glycol 45°C 105°C H 55°C HOT UTILITY BELOW PINCH POINT
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Thermal in-situ methods for bitumen production
Field Facilities
Steam Assisted Gravity Drainage (SAGD) Cyclic Steam Stimulation (CSS)Steam
Emulsion: Bitumen + Water
Steam Chamber
Steam Emulsion: Bitumen + Water
Steaming Soaking Production
Central Processing Facilities
Field Facilities Oil Treating
De‐oilingWater Treating:Lime Softening or
Evaporation
Steam Generation (OTSGs)
Emulsion: Bitumen + Water
Diluted bitumen to upgrader or sales
Diluent
Produced Water
DeoiledWaterBFW
Steam
Canada’s oil sands is the third largest proven crude oil reserve in the world, estimated at 171 billion barrels. About 80% is recoverable by in‐situ and the remaining 20% by surface mining methods.
The main thermal in‐situ method is called steam assisted gravity drainage (SAGD) where bitumen is recovered using horizontal well pairs and steam stimulation. The key parameter of a SAGD project is the steam‐to‐oil ratio (SOR) which varies from 2 to 7 depending on the quality of the reservoir and life of the well pairs.
Fossil fuels are burned to generate the required steam, which results in GHG emissions. From a well‐to‐wheels life cycle point of view, the GHG emissions for SAGD bitumen are 18% higher than Arab‐Medium crude oils.
This paper summarizes the application of Pinch Analysis on the design and retrofit of SAGD plants. Key conclusions and recommendations are:
The pinch point is caused by the hot emulsion (bitumen and produced water) coming from the well pads. Heat integration can be improved if the emulsion arrives at the central processing facility (CPF) hotter. This can be accomplished by using mechanical lift instead of gas lift so that the produced fluids don’t have to be flashed at the pad group separators. At the
Nexen Long Lake facility the produced fluids from pads with no group separators reach the CPF at approximately 180°C instead of 161°C.
Blowdown is the hottest stream (approx. 314°C in most SAGD plants). The trade‐off between water and energy conservation defines the use of this blowdown stream. At the Nexen Long Lake facility, blowdown is flashed in a two effect evaporation scheme to maximize water recovery. LP condensate is used in our bitumen upgrader which consumes considerable amounts of water due to the gasification process.
Diluent, required for the oil‐water separation, should be pre‐heated before being mixed with hot emulsion, otherwise it is impossible to design a heat exchanger network that satisfies the energy targets.
Most designers avoid pre‐heating make‐up water (brackish water) because of hardness scaling. Proper selection of the injection point can save both energy and capital.
Glycol as heating and cooling media can be minimized resulting in savings of capital and energy.
Studies have shown that the use of Pinch Analysis on the design and retrofit of a SAGD facility, as well as the switch from mechanical to gas lift, can result in energy savings close to 20%.
Canada’s oil sands is the third largest proven crude oil reserve in the world, estimated at 171 billion barrels. About 80% is recoverable by in‐situ and the remaining 20% by surface mining methods.
The main thermal in‐situ method is called steam assisted gravity drainage (SAGD) where bitumen is recovered using horizontal well pairs and steam stimulation. The key parameter of a SAGD project is the steam‐to‐oil ratio (SOR) which varies from 2 to 7 depending on the quality of the reservoir and life of the well pairs.
Fossil fuels are burned to generate the required steam, which results in GHG emissions. From a well‐to‐wheels life cycle point of view, the GHG emissions for SAGD bitumen are 18% higher than Arab‐Medium crude oils.
This paper summarizes the application of Pinch Analysis on the design and retrofit of SAGD plants. Key conclusions and recommendations are:
The pinch point is caused by the hot emulsion (bitumen and produced water) coming from the well pads. Heat integration can be improved if the emulsion arrives at the central processing facility (CPF) hotter. This can be accomplished by using mechanical lift instead of gas lift so that the produced fluids don’t have to be flashed at the pad group separators. At the
Nexen Long Lake facility the produced fluids from pads with no group separators reach the CPF at approximately 180°C instead of 161°C.
Blowdown is the hottest stream (approx. 314°C in most SAGD plants). The trade‐off between water and energy conservation defines the use of this blowdown stream. At the Nexen Long Lake facility, blowdown is flashed in a two effect evaporation scheme to maximize water recovery. LP condensate is used in our bitumen upgrader which consumes considerable amounts of water due to the gasification process.
Diluent, required for the oil‐water separation, should be pre‐heated before being mixed with hot emulsion, otherwise it is impossible to design a heat exchanger network that satisfies the energy targets.
Most designers avoid pre‐heating make‐up water (brackish water) because of hardness scaling. Proper selection of the injection point can save both energy and capital.
Glycol as heating and cooling media can be minimized resulting in savings of capital and energy.
Studies have shown that the use of Pinch Analysis on the design and retrofit of a SAGD facility, as well as the switch from mechanical to gas lift, can result in energy savings close to 20%.
Make-upWater
Lime sludge or concentrate to
disposal
Blowdown (after treatment and/or partial recycle) to
disposal
Pinch Analysis of Central Processing FacilitiesSOR = 3.0; Warm Lime Softening/OTSG; Full Blowdown Recycle; Tmin = 10°C
BFW/Wet Steam
HP Blowdown
Emulsion
Make-upWater
Dilbit & Water Disposal
In most SAGD/CSS plants, the pinch point is located at the inlet
temperature of the emulsion
Moving the pinch point: impact of lift mechanism (Gas vs. Mechanical Lift)
Emulsion to CPF
Lift Gas, Flashed Steam, Produced Gas
Casing Gas
Production
Group Separator~ 700 kPa
~165°C180-200°C
Lift Gas
Producer
Emulsion to CPF
Casing Gas to CPF (small volumes)
Production180-200°C
Producer
Gas Lift Mechanical Lift
Electrical Submersible Pump (ESP)
Natural Gas (and GHG) reduction can reach
more than 10%
Energy vs. Water Conservation
CNOOC acquisition: On February 25, 2013, Nexen announced that CNOOC Limited has completed its acquisition of Nexen, which now becomes a wholly-owned subsidiary of CNOOC Ltd. As part of the agreement, Nexen will managed CNOOC Limited’s assets in North and Central America (slide above not updated to reflect this recent news).
About Nexen
Process Integration Applied to Thermal In-Situ Oil Sands ProjectsDenis Westphalen ([email protected])
Calgary, Alberta - CanadaDevelopment Engineer, Oil Sands Planning & Economics, Nexen Inc.
If Lime Softening is used, TDS of Boiler Feed Water can be as high as 8,000 ppm which forces the use of Once Through Steam Generators (OTSGs) with steam qualities no higher than 80%. Steam is generated at high pressures (11 MPa) to save on steam lines to field facilities. HP Blowdown consists of a hot stream (~314°C) with high solids content (40,000 ppm TDS).
Design for Energy Conservation Design for Water Conservation
OTSG
Steam75-80% quality
Steam to Field
HP Blowdown ~314°C
To Disposal
Recycle
OTSG
Steam75-80% quality
HP Blowdown ~314°CGlycol cooling
MP
LP
LP Blowdown to Disposal MP Condensate
to Recycle
LP Condensateto Recycle
Steam to Field
There are several other configurations for handling HP blowdown such as one flashing level (LP), mechanical vapor recompression (MVR) evaporation, hybrid (parallel flashing heat recovery), etc. The right
configuration for a particular project is a choice between energy and water configuration and depends on Produced Water and Make-up Water qualities (TDS), water source type (fresh or brackish), Water Treatment Technology (Lime Softening or Evaporation), Disposal Methods, Project Specific Constraints and Regulatory Approvals.
Natural Gas consumption may vary in more than 15% depending on the selected scheme.
Typical Water Recycle Rate: 50 to 90%
Typical Water Recycle Rate: >98%
Do’s and Don’ts
Boiler Feed Water
Summary
Diluent:Diluent (gas condensate, naphtha, synthetic crude oil) is mixed with the emulsion to promote the water-oil separation. In most designs, cold diluent (~15°C) is mixed directly with the partially cooled emulsion. This approach is justified because it eliminates one heat exchanger. If instead, diluent is pre-heated in a heat exchanger to ~125°C (oil treating temperature), 1-2% energy savings are obtained by a better heat exchanger network design.
Make-up Water:Industry is being pushed to use more brackish water instead of fresh. Brackish water cannot be heated in a heat exchanger because of hardness precipitation. A common approach is to mix it cold with de-oiled water, which may result in additional steam consumption in a Hot Lime Softening system (any steam usage results in pinch crossing). If instead, brackish water is mixed with produced water (prior to de-oiling), no additional steam is required and savings on glycol cooling and heat exchanger size are obtained.
Glycol:During final design stage, operations representatives push the excessive use of cold and hot glycol as heat transfer media, claiming better operability – which always result in higher CAPEX and OPEX.
Dilbit120°C
Make-up Water5°C
85°C
86°C
1 Heat ExchangerLMTD = 54.8°C
Dilbit120°C
Make-up Water5°C
85°C
86°C
2 Heat ExchangersLMTD = 25.8°CLMTD = 32.7°C
C
Glycol45°C
105°C
H
55°C
HOT UTILITY BELOW PINCH POINT
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