Norwegian Experience with Sandstone Augmented Water Flooding

Transcription

1 Norwegian Experience with Sandstone Augmented Water Flooding Susanne Larsen

2 Norwegian Experience Polymer in Snorre and Gullfaks Lab experiments => low salinity flooding/ alkaline flooding Simulations Bright Water in Snorre Bright Water Design Simulations Field test? Low salinity in Heidrun and Snorre Lab experiments Simulations SWTT LPS/CDG in X field Lab experiments

3 Bright Water Concept

4 Bright Water Conceptually simulation applying temperature tracking and tracers Chemical simulators The chemicals are designed for the specific application Has primarily been applied as near well treatment. For inter-well treatment the amount of chemicals might be an obstacle

5 LPS Mechanism 40 % of remaining oil in core experiments recovered (Spildo, 2008) (Skauge,2010)

6 LPS Features Seems (also) to affect microscopic sweep Pump-able ready made solution Lower concentration Seems more salinity robust than strong gels Relatively cheap

7 Low Salinity Advantages Off-shore water softening and desalinization Reverse osmosis Designed water Placed on vessel for multi field treatment => Cheap Simple Non-toxic

8 Low Salinity Waterflooding Mechanisms => screening, laboratory work & testing Norwegian Experience Lab & Field Experience Dynamic Modelling

9 Permeability Alteration by Electro-Osmosis Theory from 1950 ies (Schleidegger,1974)

10 Osmosis Osmosis Low salt conc. P I n c High salt conc. membrane Ref 1

11 Wettability Change Change in θ 10 o Increasing Oilwetnes (Sorbie, 2010)

12 Elements WATER

13 Water SALINITY GRADIENT Secondary? Tertiary? (BP patent Application) (Austad, 2010) (Rivet, 2009)

14 Formation Formation has to be oil-wet / intermediatewet sandstone Kaolinite? (Zhang, 2006) (Lager, 2006) (Austad, 2010)

15 Oil Acid Components

16 State of the Art / Screening Criteria Sandstone formation Distributed non-swelling negatively charged clays Oil to mixed wet reservoir Injection water below some threshold salinity Which (if any) injection water composition that results in EOR has to be designed from screening experiments applying the pertinent rock-oil-brines at reservoir conditions

17 State of the Art / Laboratory Work & Testing Reservoir conditions Actual oil water and rock Trial-and-error water compositions Recommendation: Inject low salinity water after otherwise planned SCAL experiments SWTT applying most promising composition

18 Field and Test Experience

19 Recovery vs Kaolinite Content (Jerauld,2006)

20 Snorre Results (Skrettingland, 2010)

21 Heidrun Core Experiments (Heigre,2008)

22 SWTT with 20 % residual oil recovery

23 Reservoir Modelling

24 Modelling of Endicot Low Salinity Flooding Salt component implemented in BP s chemical EOR VIP simulator Viscosity and density salinity dependent Rel perm and capillary pressure made functions of salinity Dispersion modelling (Jerauld,2006)

25 Modelling of Low Salinity Water Injection Applying E100 Basically we want to shift to more waterwet rel perm curves and lower residual oil saturation when low salinity water is injected Apply different low salinity rel perm curves as function of clay content

26 Input Rel Perms as Function of C a S S C a ors orw v μ is the viscosity of the liquid v is a characteristic velocity γ is the interfacial tension between the two fluid phases log C a

27 E100 Input concentration to be picked according to the anticipated threshold for low salinity to work SURFST Surfactant concentration Water/oil surface tension lb/stb lb/in / SURFCAPD LOG10(Capillary Number) Miscibility function for C a < 10-9 high sal 10 1 / saturation tables are applied (0) for C a > 10-8 low sal saturation tables are applied (1) SURFST "Inverse salt concentrartion" IFT to be picked so the miscibility function shifts at the appropriate C a Water/oil surface tension mn/m / SURFCAPD LOG10(Capillary Number) Miscibility function /

28 Results Additional recovery was obtained Oil bank formed in front of the low salinity water End-point scaling applied as function of clay content Additional recovery low due to initially water-wet formation

29 Conclusions THE applicable explanation not yet found => poorly defined screening criteria => extensive and expensive lab experiments Can be partly mitigated by running low salinity after initial SCAL LPS or Alkaline flooding to follow SCAL? Low salinity field flooding can be modelled applying commercially available software Once an appropriate injection water salinity is identified SWTT is an important tool to Measure in-situ residual saturations Determine dispersion

30 References (Austad,2010)T. Austad, A. RezaeiDoust et al Chemical Mechanism of Low salinity Water Flooding in Sandstone Reservoirs SPE SPE IOR Symposium Tulsa April 2010 (Heigre,2008) E. Heigre Low Salinity Water Injection. Heidrun Field Case Study OWI0O/Low_Salinity_Water_Injection_Case_study_Heidrun_Field Force Seminar Paper published on net (Jerauld,2006) G.R. Jerauld, C.Y. Lin, K.J. Webb, J. C. Seccombe Modelling Low-Salinity Waterflooding SPE (Lager,2006) A. Lager, K.J. Webb et al Low salinity oil recovery An experimental investigation. SCA Presented at the society of core analysts meeting in Trondheim 2006 (Rivet,2009) S. M.Rivet Core Flooding Oil Displacements with Low salinity Brine www Ms.Sc. Thesis University of Texas (Schleidegger,1974) A. E. Schleidegger: Physics of Flow in Porous Media, Pitman Pres, Bath, UK (Skauge, 2010) A. Skauge MDT: CDG or LPS. Force Force Seminar January 2010 on Microscopic Diversion Techniques (Skrettingland, 2010) K. Skrettingland, T. Holt, M.T. Tweheyo, I- Skjeverak Snorre Low Salinity Water Injection- Core Flooding Experiments and Single Well Field Pilot SPE SPE IOR Symposium Tulsa April 2010 (Sorbie, 2010) K. Sorbie, I.R. Collins A Proposed Pore-Scale Mechanism for How Low Salinity Waterflooding Works SPE SPE IOR Symposium Tulsa April 2010 (Spildo, 2008) K. Spildo, A.Skauge et al A new Polymer Application for North Sea Reservoirs SPE (Zhang,2006) Y. Zhang, N. Morrow Comparison of secondary and tertiary recovery with change in injection brine composition for crude oilsandstone combinations. SPE