Transcript Lab and Field experience LoSal - Start

Classification: Internal
Status: Draft
Low Salinity Waterflooding: Opportunities and
Challenges for Field Pilot Tests
Dagmar Spangenberg, Peimao Zhang
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Outline
• Introduction
• Lab experiments – overview
• Field experiments – overview
• Mechanisms – discussion
• Snorre – Heidrun – Gullfaks field pilot
• Summary
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Introduction - LowSal history
• 1970s: first IOR observation (SPE 6771)
• 1990s-: studies as a stand-alone IOR method
(SPE…)
• 2004-: field experiments
– Well-Log-Injection - BP (SPE 89379)
– Single well test - BP (SPE93903)
• Polymer flooding in Daqing, China
Lab
experiments
1965-1972
Pilot
field test
1989
– Field statistics (SPE 109965)
– Field evaluation - BP (SPE 113480)
•
2008: pilot in Endicott (BP)
•
2009: possible pilot tests in Snorre or Heidrun
(StatoilHydro)
Commercial
field test
1991
Large scale
commercialization
1996
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Introduction - LowSal related activities in StatoilHydro
• R&D
– Extensive lab studies
– IOR mechanism
– Modelling tool
• Corporate IOR initiative
– Qualification of LowSal pilot tests
• Assets
– Heidrun
– Snorre
– Gullfaks
– Norne
– Partner operated fields
Snorre
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Lab experiments – overview (1)
• Typical LowSal core flooding performance
in lab (Zhang, Xie and Morrow, 2007, SPE)
– Constant rate injection
– Increase in recovery of 5-15% OOIP
– Large PVs injected
– Slight increase in effluent pH
– Significant increase then decrease in ∆P
• The LowSal recovery response, without
corresponding increase in pressure drop, is
unusual (Loahardjo et al., 2007).
• Very few experiments showed IOR potential
without significant changes in ∆P (e.g.
Heidrun)
SPE 109849
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Lab experiments – overview (2)
• LowSal: necessary conditions (Morrow et al., 1998&1999)
– Sandstone with presence of clays (but: latest findings (SPE 113410) show
positive lowsal response without clays)
– Polar organic compounds from crude oil
– Initial water saturation (core floods)
– Brine salinity: 500-5000 ppm
– Salinity contrast between connate water and invading water
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Field Experiment - Well-Log-Injection – 2004
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•
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•
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SPE 89379
Clastic reservoir, 70-95% quartz, plus kaolinite, plagioclase, illites and smectites
3000 ppm low salinity water
Variation in water saturation with depth shows low salinity achieving higher water saturation and hence
better oil recovery
Top perforated interval
– decrease of remaining oil up to 50%
•
Middle and bottom perforation
– decrease of remaining oil 10-20%
SPE 89379
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Field Experiment - BP
• BP Alaska Prudhoe Bay
– SPE 93903, 2004
• Single well tests
• Tests in 4 areas, salinity
of the water between
1500 and 3000 ppm
• Increased oil recovery
between 8 and 19% of
OOIP
SPE 93903
• Alaska Journal of Commerce, 21. October 2007
– BP will start early 2008 pilot test Endicott
– Endicott now: 65% oil recovery
– If pilot shows potential → Endicott full field implementation: 75-80% recovery
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Field Observation – Robertson, 2007
• SPE 109965
- Low Salinity
Waterflooding to improve oil
recovery – historical field
evidence
• 3 fields in Wyoming, same
formation, crude oil and
reservoir temperature very
similar, production started in
the 70’s and 80’s
(Robertson, SPE 109965)
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Field Observation – Robertson, 2007
•
•
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Results corroborate laboratory results of improved recovery from low-salinity floods
A trend in oil recovery from historical field data was identified with respect to injection water salinity
Data showed that oil recovery tended to increase as the salinity ratio of the waterflood decreases,
which generally means that lower salinity floods tended to have higher oil recoveries
Good statistics?
Salinity contrast is potentially important!
(Robertson, SPE 109965)
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Hypothetic IOR mechanisms
• Hypothetic IOR mechanism proposed in the literature
– Detachment/stripping of mobile fines/clays (Morrow et al, 1999)
– Generation of in-situ surfactants (SPE 93903)
– Multi-component ionic exchange and wettability alteration (SCA2006-36)
– Multicomponent ion exchange that causes reduction in ion binding
between the crude oil and the rock surface (Lager et al., Symposium of
Improved Oil Recovery, Egypt, 2007)
• StatoilHydro is evaluating different possible IOR mechanisms
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Strategy for qualifying LowSal for implementation
Lab study
IOR Mechanism
Upscaling of
lab results
Field pilots
Potential
evaluation
Well pair
selection
Modelling
tools
Success criteria
Full field
implementation
Economical
evaluation
Fines migration
/clay swelling?
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Upscaling Procedure to Estimate the EOR Potential
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Core flood experiments - displacement efficiency
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Pore volumes injected, salinity of the injected water, oil recovery
Method - tracer simulation
– Tracer study - sweep efficiency
– Results from the core floods and the tracer study give a possibility to
estimate the recovery improvement
•
Method – relperm curves versus salinity (SPE 102239, ref. BP)
– Two relperm-curves, one with high salinity water injection, one with low
salinity water injection
– Include both curves in ECLIPSE with a surfactant option
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Heidrun - Pilot Candidate
• Reverse osmosis plant on
the platform
• First lab results from the
Upper Tilje and Åre
formation show low salinity
water injection potential
• Simulation work is ongoing
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Snorre - Pilot Candidate
• Lab experiments ongoing
• Upper Statfjord, lower Stafjord,
Lunde Formation
• Simulation work ongoing
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Gullfaks - Pilot Candidate
• Lab experiments
ongoing
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Summary – LowSal pilots
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LowSal advantages
– High IOR potential
– Environmentally friendly
– Combination with other recovery methods possible (such as polymers, silicate, alkaline…)
•
LowSal challenges
– Upscaling from lab scale to field scale
– LowSal mechanisms not fully understood
– Costs for the production of the low salinity water
– Favourably isolated injector/producer well pair without long distance from each other
– Pore volumes injected
– Danger at too low salinity: formation damage, plugging of the pores
– Composition of the injected water important, proportion between monovalent and divalent ions
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Thank you for your attention