Aspects of Waterflooding

Transcription

1 Aspects of Waterflooding Sheena Xie, Hui Pu and Norman Morrow January 13, 21, Denver, CO

2 Projects in Progress at P&SC Group (Led by Morrow N.R.) Improved oil recovery by low salinity waterflooding - Wyoming reservoirs - Reservoirs from North Sea and Middle East - Outcrop cores for mechanism studies - Fines migration and mineral dissolution of Tensleep and Minnelusa rocks (Micro-CT imagine joint with ANU) Wettability studies - Sequential waterflooding - Capillary effect, rate effect - Spontaneous imbibition at various wettability conditions Improved polymer flooding fly ash augmentation - Screening polymer and fly ash - Optimal mixture of polymer + fly ash + additives - Transport and straining in rock fractures Improved gas recovery by wettability alteration - Wamsutter tight gas sands (joint with INL)

3 OUTLINE Sample results of improved oil recovery by low salinity waterflooding - Wyoming reservoir cores Intermittent waterflooding Leading mechanism wettability change Summary

4 Crude oil properties Minnelusa Tensleep Cottonwood Creek Density, g/ml Viscosity, cp n-c 7 Asp. wt% Formation water Concentration, mg/l Comp. Minnelusa Cottonwood Tensleep NaCl 29,83 19, 571 CaCl 2 2,14 8, Na 2 SO 4 5,93 1,765 1,312 MgSO MgCl 2-1, NaHCO ,312 TDS 38,651 3,755 3,3 CBM water Constituents Concentration, mg/l NaCl 916 KCl 28.7 MgCl CaCl TDS 1,316.3

5 Tensleep Reservoir Rock (After Yin, 27)

6 Spontaneous Imbibition of Tensleep cores R, %OOIP Tensleep 5479B K w =87md Ø=18.67% 1% mineral oil saturated VSWW Tensleep crude oil saturated VSWW 2 1.E+ 1.E+1 1.E+2 1.E+3 1.E+4 1.E+5 Dimensionless imbibition time 2 Core T2 Core T1 1.E+ 1.E+2 1.E+4 1.E+6 1.E+8 1.E+1

7 Tensleep Reservoir Cores Low salinity waterflooding at tertiary mode Initial brine: high salinity

8 Tensleep Reservoir Cores waterflooding cases Recovery, %OOIP H5 φ=9.15% Kw = 7.2 md Swi = 18.6% Tensleep Brine 33ppm +4.6% Pressure Recovery CBM Brine 1316ppm Pressure Drop, psi Recovery,% T814 Swi = 21% φ = 14.2% Kw = 8.8 md Tensleep Brine 33ppm Injected Brine, PV +7.18% CBM Brine 1316ppm Pressure Drop, psi Initial brine: low salinity Injection brine: low salinity Injected PV

9 Spontaneous imbibition of Tensleep Cores from dry well C 5515C Kg, md φ, % Tensleep oil saturated cores Oil recovery, OOIP% C 5515C Imbibition time, Days

10 Tensleep Reservoir Core 552C Low salinity waterflooding (no effect) Core from dry well Initial brine: high salinity

11 Tensleep Core H4 Effluent Analysis

12 Dolomite crystals from suspension of crushed Tensleep rock Micro-CT: Tensleep rock before and after flooded by brine 5µm Green color: dissolved during flooding

13 Minnelusa Reservoir Rock (After Yin, 29)

14 Spontaneous Imbibition of Minnelusa cores 1 15 Recovery, %OOIP Imbibition Time, Day Minnelusa Swi = 19.34% Recovery, %OOIP Minnelusa Swi = 2.28% Imbibition Time, Day

15 Minnelusa Core : Low salinity effect K g =98md Ø=13.4% S wi =13.83% Pressure 1 8 Recovery, %OOIP Minnelusa Brine 38,651ppm +4.1% CBM Brine 1,316ppm Recovery Pressure Drop, psi Brine Injected, PV Initial Brine: Minnelusa (38,651 ppm)

16 Minnelusa Core : Injection rate effect K g =292md Ø=2.68% S wi =22.75% Pressure Recovery 3 25 Recovery, %OOIP % +2.%.25ml/min 1.ml/min 4.ml/min Pressure Drop, psi Injected Brine, PV Initial Brine: Minnelusa (38,651 ppm) Injection Brine: CBM (1,316 ppm)

17 Minnelusa Core : Injection rate effect Recovery, %OOIP K g =182md Ø=18.44% S wi =11.37% Pressure Recovery Reco-.25ml/min Reco-.5ml/min Reco-.75ml/min Reco-1.5ml/min Injected Brine, PV Pressure Drop, psi Connate Brine: Minnelusa (38,651 ppm) Injection Brine: CBM (1,316 ppm)

18 Brine Permeability of Minnelusa Core (saturated with 2, ppm NaCl and displaced with the same brine) Brine Permeability, md Brine Injected, PV K g =64md Ø=5.75%

19 Cottonwood Creek Reservoir Rock 5 µ 125 µ width=132 µ (after Yin, 23)

20 Spontaneous Imbibition of Cottonwood Cores R, %OOIP Cottonwood 5672 Kw=8.6md Ø = 11.37% Swi = 34.45% VSWW Cottonwood brine (3,755 ppm) 2 times dilution (1537 ppm) 1.E+ 1.E+1 1.E+2 1.E+3 1.E+4 Dimensionless imbibition time R, %OOIP Cottonwood 5772 K w =3.9md Ø = 9.2% S wi =47.95% VSWW Cottonwood brine (3,755 ppm) 1.E+ 1.E+1 1.E+2 1.E+3 1.E+4 Dimensionless imbibition time 2 times dilution (1537 ppm)

21 Coreflood Results of Cores 58 A and 58B Cottonwood 58A S wi =48.89% Recovery, %OOIP % Recovery Pressure Pressure Drop, psi ,755ppm 1,537ppm Injected Volume, PV Initial brine: high salinity Cottonwood 58B S wi =36.27% Pressure Recovery, %OOIP % Recovery Pressure Drop, psi 2 1 3,755ppm 1,537ppm Injected Volume, PV

22 Sequential Waterflooding (Nina s talk) Intermittent Waterflooding

23 Carbonate Cores: Intermittent waterflooding 1 8 Carbonate C1 Kw = 28.4 md Swi = 21.9% 8 6 Oil Recovery, %OOIP seawater 7.6% 3.% 2 times diluted seawater 4 day intermission R P 4 2 Pressure drop, psi Brine Injected, PV Initial brine: high salinity

24 Sandstone Cores: Intermittent waterflooding Oil recovery, %OOIP Core E9 Kg = md Swi = 16.2% 12 hr intermission brine (57,95 ppm) 6.3% R 2.8% Diluted brine (2,898 ppm) Injection pressure, psi Oil recovery, %OOIP Core E8 Kg = md Swi = 15.8% brine (57,95 ppm) 12 hr intermission 3.7% Diluted brine (2,898ppm) 5.7% R Injection pressure, psi 2 P P Brine injected, PV Brine injected, PV Initial brine: high salinity

25 Sandstone Core: Intermittent waterflooding 1 Sandstone Core E1 3 day intermission Oil recovery, %OOIP R1/C1 ; Swi = 2 % R1/C2 ; Swi = 22.9 % R1/C3 ; Swi = 2 % R1/C4 : Swi = 33.1 % R1/C5 : Swi = 41.7 % No salinity change Brine Injected (PV)

26 Revisited: Suggested mechanisms for low salinity waterflooding Osmotic pressure Salinity shock Saponification Limited release of mixed-wet particles Emulsification/snap-off Particle-stabilized interfaces/lamellae Multi-component ion exchange Surfactant-like behavior Wettability alteration (more water-wet) Wettability alteration (less water-wet) Viscosity ratio (after Buckley, 29)

27 Summary Laboratory tests show that Wyoming reservoir rocks appear to be weakly water-wet. Both sandstones and dolomite have mostly responded positively to low salinity waterflooding in tertiary mode. Fines migration and mineral dissolution are important features of Tensleep and Minnelusa rocks during low salinity waterflooding; Intermittent and sequential waterflooding without salinity change indicate that water/oil re-distribution associated with wettability change and capillarity during waterflooding play key roles in improved oil recovery. The dominant mechanisms for improved oil recovery by low salinity waterflooding vary depending on the rock, the oil, the brine and their interactions.

28 Thanks You!