Low Salinity Waterflooding Fundamentals and Case Studies

Transcription

1 Low Salinity Waterflooding Fundamentals and Case Studies Norman R. Morrow Chemical & Petroleum Engineering University of Wyoming and Charlie Carlisle Chemical Tracers, Inc IOR/EOR Conference Jackson, WY September 10 11, 2012

2 Enhanced Oil Recovery Technologies The increase of ultimate recovery through injection of steam, chemicals or gas to more effectively displace the oil bringing RFs to the 50-70% range. Process Maturity R&D Discover Develop & Demonstrate Optimisation In Situ Upgrading N 2 /CO 2 Foam Hybrid Processes Microbial Deploy & Repeat Miscible Gas Thermal GOGD SAGD Polymer Flooding Low Salinity Waterflooding Alkaline Surfactant Polymer High Pressure Steam Injection Contaminated/Acid Gas Solvents In - Situ Combustion / HPAI In - Situ Upgrading (heating) (catalytic) Time Steam (SF, CSS) Integrated Solutions Mature Field Mgmt Surface+Subsurface Onshore/Offshore Smart Surveillance Wells & Resv Mgmt Operations From Shell EOR Academy, May, 2012

3 Oil Production Rate, B/D 60,000 Primary Recovery 40,000 Secondary R 20,000 Field Discovered Year Bradford Field, Pennsylvania From Waterflooding, Whillhite, 1986

4 Oil Production Rate, B/D 60,000 Primary Recovery 40,000 Waterflooding Legalized Secondary Recovery 20,000 Field Discovered Year Bradford Field, Pennsylvania From Waterflooding, Whillhite, 1986

5 WATERFLOODING Highly successful for more than 75 years Accounts for more than 50% of current US oil production Worldwide application (waterflooding is usually implemented at the outset of production). Technology involves handling very large volumes of water

6 Co-produced water Estimates of the decrease in fractional flow of oil can be obtained from production statistics for oil and water

7 Wyoming Worldwide US (including Alaska) US (lower 48 states) Average fractional flow of produced oil in the US lower 48 states is about 2% From C. Carlisle

8 Dependence of Oil Recovery on Injection Brine Composition Conventional view Injection brine composition was believed to have no effect on efficiency of oil recovery by waterflooding (apart from formation damage). Brine Composition Effects Change in brine composition at high salinity (1994) Low salinity waterflooding secondary mode (1997) tertiary mode (1999) Dissolution - especially anhydrite (2009, 2010) No change in brine composition (2008, 2009, 2012)

9 Oil Recovery (% OOIP) Laboratory Measurement of Oil Recovery by Waterflooding for Outcrop Rock and Refined Oil 100 brine core TARGET FOR TERTIARY RECOVERY For an initial water saturation of 25%: residual oil = 37.5% OIL RECOVERY BY WATERFLOOD 0 5 Injected Brine Volume (PV)

10 LSE starting at initial water saturation From Tang and Morrow 1999

11 June 1995 The British Petroleum Research Center sent their representative, Cliff Black, for a three day think tank session.

12 100 CS Crude Oil/CS Brine/Berea Rwf (% OOIP) S wi =23-27 % T a =55 C t a =7.0 days T d =55 C Flood rate=10 ft/d connate=invading 0.01CSRB 0.1CSRB CSRB Injected Water Volume (PV) EFFECT OF DILUTION OF BOTH CONNATE AND INVADING BRINES ON OIL RECOVERY BY WATERFLOODING From Tang and Morrow 1999

13 CS Crude Oil/CS Brine/CS Sandstone CSRB=connate Rwf (% OOIP) invading brine CSRB 0.01 CSRB S wi =25% T a =55 o C t a =10 days T d =55 o C flood rate=6ft/d Injected Brine Volume (PV) EFFECT OF THE CONCENTRATION OF INJECTION BRINE ON WATERFLOOD RECOVERY FOR RESERVOIR CORE From Tang and Morrow 1999

14 Application of LSW to recovery of oil from watered-out reservoirs at residual oil saturation after high salinity waterflooding

15 Tertiary response to low salinity brine 100 LC crude oil, Swi = 10.6% R3:C R wf, %OOIP R 12.6% 10 5 D P, psi 20 Zhang, et al 2007 (SPE ) 0 RIB (29,690 ppm) D P LSB (1,480 ppm) Brine injected, PV

16 Pilot tests of low salinity waterflooding

17 BP: All clastic reservoir systems reported have shown an average of 12% incremental oil recovery through mobilization of residual oil So Hisal So Losal DSot 100% S S o initial o Hisal

18 Application of LSW secondary mode Injection of low salinity water at the outset of reservoir development (especially when membrane separation infrastructure is needed for removal of sulfate)

19 Low Salinity Waterflooding - Mechanism 19

20 NECESSARY CONDITIONS FOR SENSITIITY OF OIL RECOVERY TO BRINE COMPOSITION Adsorption of polar components from crude oil the presence of connate water The presence of clay (kaolinite)

21 NO SENSITIVITY TO SALINITY WAS OBSERVED IF: the oil phase was a refined oil if the core did not contain an initial water saturation if the core was fired and acidized in order to destroy the kaolinite clay structure. (Tang & Morrow, 1999)

22 adsorbedpolaroil components water oil oil oil clay clays solid water a. adsorptionontoclaysurface b. clayparticle AdsorptionofPolarComponentsfromCrudeOil and MobilizedClayParticlesatBrine/Oil Interface From Tang and Morrow 1999

23 transitiontowards increasedwater-wet mobilizedmixed-wet clayparticles water oil solid water-wet clayparticles EfectofClayWetabilityonRetainedOil From Tang and Morrow 1999

24 water oil retainedoil water solid a. retainedoil before dilutebrinefloding b. retainedoilsbecome mobilizedueto detachedclayparticles DetachmentofMixed-WetClayParticlesand MobilizationofOilDrops From Tang and Morrow 1999

25 Mechanism - Limited Mobilization of Fine Particles (Kaolinite) Tang and Morrow, JPSE, 1999 There are now numerous examples of LSW for which production of fine particles is not observed. However, the number of submicron particles in sandstone that change location during waterflooding has been demonstrated to increase with decrease in salinity (Fogden, Kumar, Morrow, Buckley, Energy & Fuels 2011).

26 SEM imaging: Single-phase flooding Berea B1 Before : 97x73 mm 2, scale bar 10 mm From Kumar, et al. Petrophysics 2011

27 Berea B1 After : 97x73 mm 2, scale bar 10 mm From Kumar, et al. Petrophysics 2011

28 Low Salinity Effect (LSE) Many laboratories and organizations have grappled with identifying, reproducing, and explaining LSE Morrow and Buckley, 2011

29 Number of papers McGuire et al Lager et al Year Interest in LSW has increased as indicated by the number of publications and presentations focused on the low salinity effect (LSE). Updated from Morrow and Buckley, JPT, 2011

30 Mechanism? Despite growing interest in LSE, and consensus that improved recovery can be obtained by Low Salinity Waterflooding (LSW), a consistent mechanistic explanation has not yet emerged

31 Necessary conditions for LSE (Tang and Morrow 1999) a significant clay fraction, the presence of connate water, and exposure to crude oil to create mixed-wet conditions. Problem! In many instances these conditions are not sufficient. Further investigation is needed but the type of Berea sandstone used in the original mechanistic studies has been unavailable for over ten years.

32 Quest for Responsive Outcrop 17 outcrop sandstones and 6 outcrop carbonates have been tested for LS response From Winoto, et al SPE

33 Tests of low salinity response of outcrop sandstones Tertiary mode tests on all 17 cores for mobilization of residual oil by LSW. Tertiary mode recovery is readily tested in the laboratory because response is observed directly as additional recovery after change in injection brine From Winoto, et al SPE

34 Oil Recovery, %OOIP Laboratory Measurement of Tertiary Mode Oil Recovery by Waterflooding 100 brine core at S wi Tertiary Recovery by Injection of Diluted Brine Oil Recovery by Waterflood Brine Injected, PV

35 LSE at S or for 17 outcrop sandstones From Winoto, et al SPE

36 Comparison of LSE at S or for outcrop and reservoir sandstones avg DS ot = 12.1% avg DS ot = 3.9% From Winoto, et al SPE

37 Data have also been obtained at UW for 11 sandstone reservoir crude oil/brine/rock combinations 37

38 Comparison of LSE at S or for outcrop and reservoir sandstones avg DS ot = 11.1% avg DS ot = 12.1% avg DS ot = 3.9% From Winoto, et al SPE

39 Summary Overall, reservoir rocks respond better to LS flooding than outcrop rocks Identification of the sufficient conditions for LSE remains as an outstanding challenge. The search for outcrop sandstones that show LS response comparable to the magnitude observed for reservoirs is being continued Field wide application of LS flooding is being implemented

40 FIELD APPLICATIONS Injection of selected brine at the beginning of a waterflood Change injection brine during the course of a mature waterflood Decide if produced brine (initially the reservoir connate brine composition) should be reinjected Each situation should be carefully tested in the laboratory at reservoir conditions. The type of results that have been shown provide guidance in selection of brine composition, but recovery efficiency may depend on competing interactions for specific situations.

41 Application of Coalbed Methane Water to Low Salinity Waterflooding of Three Wyoming Formations

42 Targeted Formations Tensleep and Minnelusa aeolian sandstones One half of Wyoming s oil production Abundant dolomite & anhydrite cement No measurable clay Formation water salinity: 3,300 38,650 ppm Phosphoria dolomite formation Recovery factor as low as 10% Patchy anhydrite No measurable clay Formation water salinity: 30,755 ppm From Pu et al., 2010 SPE

43 Low Salinity Water WY coalbed methane water (CBMW): 300 2,000 ppm CBMW used in this study: 1,316 ppm Diluted Phosphoria formation water: 1,537 ppm From Pu et al., 2010 SPE

44 Lincoln Park Teton Washakie Natrona Converse Niobrara Albany Platte Uinta Carbon Laramie

45 Tensleep Rock from Oil Reservoir 100 mm quartz Dolomite dolomite anhydrite Mineralogy: sandstone with dolomite and anhydrite cements Porosity: % Permeability: md From Pu et al., 2010 SPE

46 Oil recovery, %OOIP Pressure drop, psi Waterflooding: Tensleep Core from Oil Zone T4 K g = 22.9 md, f = 12.5% S wi = 15.3% K we1 = 0.53 md +5.2% K we2 = 0.55 md MW 38,651ppm CBMW 1,316ppm Brine injected, PV 10 0 From Pu et al., 2010 SPE

47 Minnelusa Rock from Oil Reservoir 100 mm Dolomite Dolomite Anhydrite Mineralogy: sandstone with dolomite and anhydrite cements Porosity: % Permeability: md From Pu et al., 2010 SPE

48 Oil recovery, %OOIP Pressure drop, psi Minnelusa Core Waterflooding M1 K g = 78.4 md, f = 14.6% S wi = 8.2%, % MW (38,651ppm) CBMW (1,316ppm) Brine injected, PV 0 From Pu et al., 2010 SPE

49 Phosphoria Rock from Cottonwood Creek Field 100 mm Vug Dolomite Dolomite Mineralogy: Crystaline dolomite and patchy anhydrite Porosity: % Permeability: md From Pu et al., 2010 SPE

50 Oil recovery, %OOIP Pressure drop, psi Phosphoria Rock Waterflooding P1 K g = 6.8 md, f = 9.5% S wi = 22.7% K we1 = 2.1 md K we2 = 1.1 md % PW 30,755ppm Brine injected, PV 5% PW dilute 1,537ppm 5 0 From Pu et al., 2010 SPE

51 Oil recovery, %OOIP Pressure drop, psi Phosphoria Rock Waterflooding P2 K g = md, f = 19.6% S wi = 23.1% K we = 9.4 md PW 30,755ppm 5% PW dilute 1,537ppm % Brine injected, PV 0 From Pu et al., 2010 SPE

52 Tensleep Rock from Aquifer Minimal Anhydrite 100 mm Dolomite Dolomite Mineralogy: sandstone with interstitial dolomite crystals Porosity: % Permeability: md From Pu et al., 2010 SPE

53 Oil recovery, %OOIP Pressure drop, psi Waterflooding: Tensleep Core from Aquifer Core# K g (md) f S wi (%) TA TA K we = 1.1md DP TA MW 38,651ppm CBMW 1,316ppm R TA1 R TA K we = 10.4 md DP TA Brine injected, PV 0 From Pu et al., 2010 SPE

54 Recovery, %OOIP DP, psi Tensleep: 31 PV of 15% HCl Wt reduction: wt%; f: - 5%, Kw: 18 md 90 md Core T3 K w = 90md, S wi =35.39% R DP Formation water CBM water Brine Injected, PV 0 From Pu et al., 2010 SPE

55 Micro - CT on Tensleep Rock: Dissolution by CBM Waterflooding Lebedeva, Senden, Knackstedt and Morrow, 2009

56 Summary Tensleep and Minnelusa sandstones, and Phosphoria dolomite all contained anhydrite and all responded to low salinity waterflooding Increase in pressure drop was usually observed before and after injection of low salinity water for cores containing anhydrite.

57 Summary After flushing with acid, Tensleep sandstone no longer responded to low salinity waterflooding Tensleep sandstone from an aquifer did not contain anhydrite and did not respond to low salinity waterflooding

58 Optimization of injection brine compositions (both low and high salinity) Much improved engineering of waterfloods will result from development of broad understanding of the factors that determine waterflood recoveries for crude oil/brine/rock combinations for wide ranges of ionic strength and composition. smart water designer brines optimized brines

59 Funding for this research was provided by: Enhanced Oil Recovery Institute and the Wold Chair Endowment at the University of Wyoming, BP, Chevron, Saudi Aramco, Statoil, and Total