polymer flooding
TRANSCRIPT
Bohai Bay, China
Present by : Behzad Hosseinzadeh
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Polymer Flooding
Number of slides:17 Winter-1392 EOR course
Reservoir Location
• Bohai Sea, also known as Bohai Gulf, Bohai, or Bo Hai, is the innermost gulf of the Yellow Seaon the coast of Northeastern and North China.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Reservoir Location
• SZ36-1 oilfield is located at the coast of Liaodong, Bohai Bay, China 9
• It is estimated that around 70% of oil reserve in China offshore oilfields are heavy oil
• 64% of them are discovered in Bohai bay.
• The oil recovery by water flooding is only 18 –25%, which is far below than that of the onshore the average oil recovery of 32 –40%.
• It was put into operation since 1993
• Sea water with high salinity of 32,423mg/L was initially injected for about 8 years.
• Then water from Guantao formation with salinity of 9048mg/L was injected.
• The history of water injection makes the salinity of produced water higher than that of the original formation water, especially of Ca 2+ and Mg 2+ .
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Rock and reservoir properties
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Rock and reservoir properties o Distributioned and good connectivity
o sedimentary rhythmic feature
o reservoir rocks are feldspathic quartz sand composed mainly of fine sands
o The crude oil in SZ36-1 oilfield is highly viscous
o It is characterzed as high desity, low sulphurcontent, low wax content and high gum and bitumen contents.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
ChallengesHigh salinity and hardness of the make-up water (Ca
2+ and Mg 2+ : 600 – 1,200mg/L), and high viscosity of oil (in average of 70mPa·s), which require the polymer to be salt resistant and good viscosification.
Limited spacing of platform does not allow big volume installation for polymer resolving, so development of fast-resolving polymer is necessary.
Drilling and completion by wire wrapped screen gravel-packed sand control and large displacement of offshore oilfields require strong anti-mechanical degradation ability of polymer.
Long-term stability of polymer in the formation is required because of the large well spacing and thick pay zone.
Treatment of produced fluid to meet the environmental requirements should fast and complete in the platform. So the effect of polymer to the produced fluid should be considered in the polymer design.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Use PHP instead of HAWPPartially hydrolyzed Polyacrylamide (PHP) is a
long chain high molecular weight polymer with great visocification
Partially hydrolyzed Polyacrylamide (PHP) is a long chain high molecular weight polymer with great visocification
a kind of Hydrophobically Associating Water-soluble Polymer (HAWP) is being designed and synethesized with less sensitive to sanilityand high viscosification as a driving agent for offshore polymer flooding.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Characteristics of HAWP
Overcoming the five main challenges is crucial for a successful offshore polymer flooding. HAWP is discussed and shows its characteristics satisfying the requirement of offshore operation.
Vicosification
Solubility
Mechanical degradation
Long-term thermal stability
Treatment of produced fluid contained HAWP
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
VicosificationThe use of water soluble polymers to increase
the water viscosity has been shown to be an effective way to improve the sweep efficiency and hence increasing the oil recovery.
The experimental result shows that visosocity of HAWP increased significantly with the increase of concentration of polymer solution. (test on J3 well of SZ36-1 oilfield)
C* = increased sharply with the increase of polymer concentration.
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C*
Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
SolubilityBecause there is a small portion of
hydrophobic comonomer introduced into HAWP, the resolving of HAWP become conditional.
Experimental result shows higher polymer concentration and higher temperature are favorable for the resolving of HAWP.
There is a critical resolving temperature for HAWP about 37 °C.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Mechanical degradation It is known that when a polymer solution is
exposed to high shear conditions the molecule may be scissored.
High shear conditions occur:during mixing of polymer solutions, or during the conveyance of a polymer solution in pumps and chokes, or during injection in perforations, or in the formation near the well bore where the polymer solution is flowing at high velocities.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Long-term thermal stability Normally a polymer flooding project would last
for years, which requires polymer stable throughout these long periods.
When polymer solution is kept for a longer period at high temperature
it can degrade and lose its viscosity.
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Treatment of produced fluid contained HAWP Produced fluid containing polymer should be
treated in the limited spacing of platforms, while meeting the requirement of reinjection to the well or discharge to the sea.
Problem :
Existence of polymers, the contained oil in the produced water increased a lot, which would lead to the hard demulsification and increamental of viscosity of produced fluid.
Solution :
A new demulsifier and assitant-demulsifier for offshore application has been developed to dehydrate water from the oil-water emulsions 13
Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Treatment of produced fluid contained HAWP
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
OperationArea was decided with a five-spot pattern.
Since October 2005, polymer flooding for well group has been carried out.
The project is designed to continuous inject HAWP for 3 years
Total polymer consumed 3,142.7tons
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Resultwater cut decreased and oil production increased in
the corresponding wells.
The accumulated oil reached 25,000m 3 and water cut decreased from 95% to 54% until the end of the test (in J3 well of SZ36-1 ).
Until Feb. 2007, the total incremental oil by polymer flooding reached 12,000m 3 , and total production kept stable (group wells)/
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Reservoir Location
Rock and reservoir properties
Challenges
Use PHP instead of HAWP
HAWP
- Vicosification
- Solubility
-Mechanicaldegradation
-Long-termthermalstability
• Treatment HAWP
Operations
Results
Thanks For Your Attention
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