2008_05_15 Dagmar Spagenberg by liwenting

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									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
                                                                                        3




Introduction - LowSal history
• 1970s: first IOR observation (SPE 6771)             • Polymer flooding in Daqing, China
• 1990s-: studies as a stand-alone IOR method                         Lab
    (SPE…)                                                         experiments
                                                                    1965-1972
• 2004-: field experiments
       – Well-Log-Injection - BP (SPE 89379)                           Pilot
                                                                     field test
       – Single well test - BP (SPE93903)                              1989

       – Field statistics (SPE 109965)
                                                                   Commercial
       – Field evaluation - BP (SPE 113480)                         field test

•   2008: pilot in Endicott (BP)                                       1991


•   2009: possible pilot tests in Snorre or Heidrun
                                                                    Large scale
    (StatoilHydro)                                               commercialization

                                                                       1996
                                                       4




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
      – Snorre
      – Gullfaks
      – Norne
      – Partner operated fields
                                                          5




 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
                                                                                6




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
                                                                                                          7




Field Experiment - Well-Log-Injection – 2004
•   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
                                                                                       8




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
                                                            9




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)
                                                                                                                 10




Field Observation – Robertson, 2007
•   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)
                                                                               11




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

                                  Well pair
   Field pilots    Potential      selection
                   evaluation
                                  Modelling
                                   tools

                                  Success criteria
    Full field    Economical
                                  Fines migration
 implementation   evaluation
                                   /clay swelling?
                                                                                   13




Upscaling Procedure to Estimate the EOR Potential
•   Core flood experiments - displacement efficiency
         •   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
                                     15




Snorre - Pilot Candidate
• Lab experiments ongoing
• Upper Statfjord, lower Stafjord,
 Lunde Formation
• Simulation work ongoing
                             16




Gullfaks - Pilot Candidate
• Lab experiments
 ongoing
                                                                                                       17




Summary – LowSal pilots
•   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

								
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