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Low Salinity Waterflooding Fundamentals and Case Studies

Norman R. Morrow Chemical & Petroleum Engineering

University of Wyoming

and

Charlie Carlisle Chemical Tracers, Inc.

2012 IOR/EOR Conference Jackson, WY September 10 – 11, 2012

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.

In Situ Upgrading (catalytic)

Process Maturity

R&D

‘Discover’

‘Develop’ & ‘Demonstrate’ Optimisation

‘Deploy’ & Repeat

N 2 /CO 2 Foam

Thermal GOGD

Contaminated/Acid Gas

In - Situ Combustion / HPAI

Polymer Flooding

High Pressure Steam Injection

Alkaline Surfactant Polymer

Hybrid Processes Microbial

Time

Steam (SF, CSS)

Miscible Gas

Low Salinity Waterflooding

SAGD

Integrated Solutions • Mature Field Mgmt • Surface+Subsurface • Onshore/Offshore • Smart Surveillance • Wells & Resv Mgmt • Operations

Solvents

In - Situ Upgrading (heating)

From Shell EOR Academy, May, 2012

20,000

40,000

60,000

Oil

Pro

du

cti

on

Rate

, B

/D

1850 1900 1950 2000

Field Discovered

Year

Bradford Field, Pennsylvania

Primary Recovery

Secondary Recovery

From Waterflooding, Whillhite, 1986

Bradford Field, Pennsylvania

20,000

40,000

60,000

Oil

Pro

du

cti

on

Rate

, B

/D

1850 1900 1950 2000

Waterflooding

Legalized

Field Discovered

Year

Primary Recovery

Secondary Recovery

From Waterflooding, Whillhite, 1986

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

Co-produced water

Estimates of the decrease in

fractional flow of oil can be

obtained from production

statistics for oil and water

US (including Alaska)

Worldwide

0

.1

.2

.3

.4

US (lower 48 states)

Wyoming

Average fractional flow of produced oil

in the US lower 48 states is about 2%

From C. Carlisle

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)

brine core

0

20

40

60

80

100

0 5

Injected Brine Volume (PV)

Oil

Reco

very

(%

OO

IP)

OIL RECOVERY BY WATERFLOOD

TARGET FOR

TERTIARY RECOVERY

Laboratory Measurement of Oil Recovery by Waterflooding for Outcrop Rock and Refined Oil

For an initial water

saturation of 25%:

residual oil = 37.5%

LSE starting at initial water saturation

From Tang and Morrow 1999

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

EFFECT OF DILUTION OF BOTH CONNATE

AND INVADING BRINES ON OIL RECOVERY

BY WATERFLOODING

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15

Injected Water Volume (PV)

Rw

f (%

OO

IP)

0.01CSRB

0.1CSRB

CSRB

CS Crude Oil/CS Brine/Berea

Sw i=23-27 %

Ta=55 °C

ta=7.0 days

Td=55 °C

Flood rate=10 ft/d

connate=invading

From Tang and Morrow 1999

0

10

20

30

40

50

60

70

80

90

100

0 1 2 3 4 5 6 7 8 9 10 11Injected Brine Volume (PV)

Rw

f (%

OO

IP)

CSRB

0.01 CSRB

CS Crude Oil/CS Brine/CS Sandstone

Swi=25%

Ta=55 oC

ta=10 days

Td=55 oC

flood rate=6ft/d

invading brine

EFFECT OF THE CONCENTRATION OF INJECTION

BRINE ON WATERFLOOD RECOVERY FOR

RESERVOIR CORE

CSRB=connate

From Tang and Morrow 1999

Application of LSW to recovery of oil from

watered-out reservoirs at residual oil saturation

after high salinity waterflooding

Tertiary response to low salinity brine

0

20

40

60

80

100

0 5 10 15 20 25

Brine injected, PV

Rw

f ,

%O

OIP

0

5

10

15

D P

, p

si

LC crude oil, Swi = 10.6%

R

D P

RIB (29,690 ppm)

LSB (1,480 ppm)

12.6%

R3:C3

Zhang, et al 2007 (SPE 109849)

Pilot tests of low salinity waterflooding

BP: All clastic reservoir systems reported have shown

an average of 12% incremental oil recovery through

mobilization of residual oil

100%o Hisal o Losal

ot

o initial o Hisal

S SS

S S

D

Injection of low salinity water at the outset of reservoir

development

(especially when membrane separation infrastructure

is needed for removal of sulfate)

Application of LSW – secondary mode

19

Low Salinity Waterflooding - Mechanism

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)

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)

adsorbed polar oil components

Adsorption of Polar Components from Crude Oil and

Mobilized Clay Particles at Brine/Oil Interface

oil

water

solid

clays

a. adsorption onto clay surface

oil

b. clay particle

clay

oil

water

From Tang and Morrow 1999

Effect of Clay Wettability on Retained Oil

mobilized mixed-wet clay particles

oil

water-wet clay particles

water

solid

transition towards

increased water-wet

From Tang and Morrow 1999

oil

retained oil

a. retained oil before dilute brine flooding

b. retained oils become mobilizeed due to detached clay particles

solid

water

Detachment of Mixed-Wet Clay Particles and Mobilization of Oil Drops

water

From Tang and Morrow 1999

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).

Berea B1 “Before”: 97x73 mm2, scale bar 10 mm

SEM imaging: Single-phase flooding

From Kumar, et al. Petrophysics 2011

Berea B1 “After”: 97x73 mm2, scale bar 10 mm

From Kumar, et al. Petrophysics 2011

Many laboratories and organizations have

grappled with identifying, reproducing, and

explaining LSE

Low Salinity Effect (LSE)

Morrow and Buckley, 2011

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

Year

Num

be

r o

f p

ap

ers

McGuire et al. 2005

Lager et al. 2006

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

(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.

Necessary conditions for LSE

Quest for Responsive Outcrop

17 outcrop sandstones and

6 outcrop carbonates

have been tested for LS response

From Winoto, et al. 2012 SPE 154209

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. 2012 SPE 154209

brine core at Swi

Laboratory Measurement of Tertiary

Mode Oil Recovery by Waterflooding

0

20

40

60

80

100

0 2 4 6 8 10 12

Oil

Re

co

ve

ry, %

OO

IP

Brine Injected, PV

Oil Recovery

by Waterflood

Tertiary Recovery

by Injection

of Diluted Brine

LSE at Sor for 17 outcrop sandstones

From Winoto, et al. 2012 SPE 154209

avg DSot

= 12.1%

Comparison of LSE at Sor for outcrop

and reservoir sandstones

avg DSot

= 3.9%

From Winoto, et al. 2012 SPE 154209

37

Data have also been obtained at UW for

11 sandstone reservoir crude oil/brine/rock

combinations

Comparison of LSE at Sor for outcrop

and reservoir sandstones

avg DSot

= 3.9%

avg DSot

= 11.1%

avg DSot

= 12.1%

From Winoto, et al. 2012 SPE 154209

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

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.

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

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 134042

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 134042

Teton

Park

Natrona W

ashakie

Uinta

Lin

coln

Carbon

Albany

Converse

Platte

Laramie

Niobrara

100 mm

Tensleep Rock from Oil Reservoir

quartz

dolomite

anhydrite

Mineralogy: sandstone with dolomite and anhydrite cements

Porosity: 8.6 -15.7%

Permeability: 7.0 – 42.7 md

Dolomite

From Pu et al., 2010 SPE 134042

0

10

20

30

40

50

60

70

80

90

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60 70

Pre

ssure

dro

p,

psi

Oil

recovery

, %

OO

IP

Brine injected, PV

T4

Kg = 22.9 md, f = 12.5%Swi = 15.3%

MW38,651ppm

CBMW1,316ppm

Kwe2 = 0.55 mdKwe1 = 0.53 md

+5.2%

Waterflooding: Tensleep Core from Oil Zone

From Pu et al., 2010 SPE 134042

Minnelusa Rock from Oil Reservoir

100 mm

Mineralogy: sandstone with dolomite and anhydrite cements

Porosity: 12.2 -18.1%

Permeability: 63.7 – 174.2 md

Dolomite

Anhydrite

Dolomite

From Pu et al., 2010 SPE 134042

Minnelusa Core Waterflooding

0

5

10

15

20

25

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18

Pre

ssu

re d

rop

, psi

Oil

reco

very

, %

OO

IP

Brine injected, PV

M1

Kg = 78.4 md, f = 14.6%

Swi = 8.2%,

MW (38,651ppm) CBMW (1,316ppm)

+5.8%

From Pu et al., 2010 SPE 134042

Phosphoria Rock from Cottonwood Creek Field

100 mm

Mineralogy: Crystaline dolomite and patchy anhydrite

Porosity: 9.5 -19.6%

Permeability: 0.25 – 294 md

Dolomite Vug Dolomite

From Pu et al., 2010 SPE 134042

0

5

10

15

20

25

30

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40 45 50

Pre

ssure

dro

p,

psi

Oil

recovery

, %

OO

IP

Brine injected, PV

PW30,755ppm

5% PW dilute1,537ppm

P1

Kg = 6.8 md, f = 9.5%Swi = 22.7%

+8.1%

Kwe1 = 2.1 md

Kwe2 = 1.1 md

Phosphoria Rock Waterflooding

From Pu et al., 2010 SPE 134042

0

1

2

3

4

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Pre

ssu

re d

rop

, psi

Oil

reco

very

, %O

OIP

Brine injected, PV

P2

Kg = 293.9 md, f = 19.6%

Swi = 23.1%

+5.5

%

PW

30,755ppm 5% PW dilute

1,537ppm

Kwe = 9.4 md

Phosphoria Rock Waterflooding

From Pu et al., 2010 SPE 134042

100 mm

Tensleep Rock from Aquifer – Minimal Anhydrite

Mineralogy: sandstone with interstitial dolomite crystals

Porosity: 17 -18.7%

Permeability: 50.8 – 228.5 md

Dolomite

Dolomite

From Pu et al., 2010 SPE 134042

0

5

10

15

20

25

30

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Pre

ssure

dro

p,

psi

Oil

recovery

, %

OO

IP

Brine injected, PV

MW38,651ppm

CBMW1,316ppm

Core# Kg (md) f Swi (%)TA1 228.5 18.7 22.4TA2 50.8 18.1 20.4

RTA1

RTA2

DPTA2

DPTA1

Kwe = 10.4 md

Kwe = 1.1md

Waterflooding: Tensleep Core from Aquifer

From Pu et al., 2010 SPE 134042

Tensleep: 31 PV of 15% HCl

Wt reduction: - 5.1 wt%; f: - 5%, Kw: 18 md 90 md

0

1

2

3

4

5

6

7

8

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

DP, p

si

Reco

very

, %

OO

IP

Brine Injected, PV

R

Core T3

K w = 90md, S wi =35.39%

Formation water CBM water

DP

From Pu et al., 2010 SPE 134042

Micro - CT on Tensleep Rock:

Dissolution by CBM Waterflooding

Lebedeva, Senden, Knackstedt and Morrow, 2009

• 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.

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

Summary

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”

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