Georg Warrlich, Ibrahim Al-Waili, Dhiya Said,

Mohamed Diri, Nabil Al-Bulushi, Jonathan

Strauss, Mohammed Al-Kindi, Fahad Al-

Hadhrami, Ton van Heel, John van Wunnik

(PDO)

Bert-Rik de Zwart, Carl Blom, Rifaat Al-Mjeni,

Paul Boerrigter

(Shell Technology Oman)

SPE-155546

PDOs EOR Screening Methodology for Heavy-Oil

Fractured Carbonate Fields - a Case Study

Talk Outline

Introduction heavy-oil fractured carbonates in PDO & field under study

EOR Screening Methodology

Global Analogues

Key Technical Risks to developments

De-risking EOR recovery methods with Appraisal

Conclusions

Top Haushi structure map - blue is deep, red is shallow ( courtesy of M. Lawati)

N

Fractured Shuaiba Fields in the Ghaba Salt Basin

Salt-withdrawal syncline

10 km

C: Cold GOGD

A: SAGOGD

B: SAGOGD

D Cold GOGD

F: This paper

500cp

250cp

8cp

9/30cp

E: SAGOGD

10000cp

5000cp

Introduction

6 fields in PDO's portfolio of

heavy-oil fractured carbonate

reservoirs in Ghaba Salt Basin

Recovery methods:

Cold & steam-assisted gas-

oil gravity drainage

Development projects in various

stages of maturity

Focus on finding a suitable

recovery mechanism for Field F

RZ

4

Res. Zone

Haw

ar

Sh

ua

iba

Rese

rvo

ir

Wate

r-fille

d R

ese

rvo

ir r

ocks

Tig

ht

Lim

esto

ne

Sat.

Oil

Porosit

y

GR

F-1

F-3

F-2

F-5

F10 F-9

F-8

F-7

F-6

Field F

Field D

Kh

ara

ib

Field F Summary – Understanding at Study Start

Large STOIIP

400m column, but only 30m thick

reservoir

Fractured Carbonate Reservoir (Shuaiba)

High porosity (28%), low perm.(5-20 mD)

Very viscous oil 10000 cp (@ 50 degC)

Low oil saturations (80% - 20%)

AGS-1H1

AGS-3H1

AGS-3H2AGS-3H3

AGS-1H2

THSU

FU2

THKHBase Hawar

THSU

FU2FU2

FU2

THKHBase Hawar

THSU

FU2THKHBase Hawar

THSUTHSU

AGS-4H1

AGS-4H2

AGS-4H3

THSU

THSU

THSU

FU2

THKH

AGS-2H1

AGS-2H2THSU

FU2

THKH

Base Hawar

THSUFU2

AG-20H1AG-4H1

AGS-2H1

AGS-3H1

THSU

FU2

THKHBase Hawar

THSU

FU2THKHBase Hawar

THSU

FU2THKHBase Hawar

THSU

FU2THKHBase Hawar

1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800

-640

-600

-560

-520

-480

-440

-400

-360

-320

0 200 400 600 800 1000m

1:16000

6300 6400 6500 6600 6700 6800 6900 7000 7100 7200 7300 7400 7500 7600 7700

-800

-780

-760

-740

-720

-700

-680

-660

-640

-620

0 100 200 300 400 500m

1:8000

14960 15040 15120 15200 15280 15360 15440 15520 15600 15680 15760 15840

-400

-380

-360

-340

-320

-300

0 50 100 150 200 250m

1:5000

400 800 1200 1600 2000 2400 2800 3200 3600 4000 4400 4800 5200

-560

-520

-480

-440

-400

-360

-320

-280

-240

0 250 500 750 1000 1250m

1:27500

F-3

F-1

Oil Sat logs

EOR Screening Methodology

Fullfield feasibility study carried out to screen all potentially applicable

recovery mechanisms within one year

1. Global benchmarking against analogue field developments & studies

2. Initial identification of potential recovery mechanisms & key risks + high-

level screening

3. Targeted appraisal campaign to address key risks to developments =>

phased field trials

4. Technical evaluation of do-ability of considered recovery mechanisms in field

F

5. Economic screening to define required commercial conditions to make a full-

field project viable

Detailed EOR Screening

Gradio

Interference testing

Analogue studies Key Technical

risks identified

Analogues Studies

Gradio

Interference testing

Analogue studies

Steam Projects Wordwide

1

10

100

1,000

10,000

100,000

10 20 30 40 50 60

Porosity [%]

Perm

eabili

ty [

mD

]

1 - 10 cp

10 - 100 cp

100 - 1000 cp

1000 - 10 000 cp

10 000 cp + (Unconsolidated Sand)

Word-wide Successful Steam Project Matrix Properties & Viscosities

Global ongoing thermal EOR projects:

90% steam, sandstone reservoirs

Similar viscosities as F:

Only in un-fractured sandstone reservoirs with permeabilities > 1 D

2 orders of magnitude greater than F matrix permeabilities

Data from Moritis, Oil & Gas Journal, 2010

Colour-coding by Viscosity

Fields with

similar

viscosity as

F, non

fractured,

Sand

F

Comparison with Carbonate Heavy Oil fields

F

Viscosity

Thickness Viscosities

<1000cp F thinner than any other

reservoir

Only 5 other fields with

viscosities >1000cp

=> F very unique &

unfavourable reservoir

properties

Data from Oil & Gas Journal’s 2010 worldwide EOR project review

(Moritis, 2010), C&C Reservoirs online proprietary data bases and

Buza, 2008

1

10

100

1000

10000

100000

0 5 10 15 20 25 30 35

Matrix Porosity [%]

Perm

eab

ilit

y [

mD

]

5 - 10cp

10 - 100cp100 - 1000cp

>1000Frac Perm

Carbonate Analogues

1

10

100

1000

10000

100000

0 5 10 15 20 25 30 35

Matrix Porosity [%]

Per

mea

bilit

y [m

D]

5 - 10cp

10 - 100cp100 - 1000cp

>1000Frac Perm

Fracture

Perms

Grosmont

Ku-e-Mond

Issaran

S

Reported

matrix-only

Production

Matrix

Perms

1

10

100

1000

10000

100000

0 5 10 15 20 25 30 35

Matrix Porosity [%]

Perm

eab

ilit

y [

mD

]

5 - 10cp

10 - 100cp100 - 1000cp

>1000Frac Perm

AG

S

F permeabilities

lowest (matrix and

fracture)

=> F very unique and

unfavourable matrix

and fracture

properties F

F

Key Risks

Key Technical

risks identified

Gradios

Analogue studies

Eliminated

by Initial

Screening

Risk/Opp

1 Fault

Leak

2

Base

seal

leak

3 Fracture

Density

4 Mobile

water

5

Low

matrix

perm

6 Sat. Oil

7 Water

supply and

disposal

SA

GO

GD

A

lt T

he

rma

l

ISC

C

he

mic

al

Rank

1

7

5

4

3

2

6

UNCERTAINTIES underlying the Risks identified pre Appraisal

D F

? ? ?

?

?

?

?

1

2

3

4

5 ?

Main Boundary

Fault

So ~

80%

So ~

20%

40

0m

30m

N S

Showstopper

per Recovery

Process

Opportunity

Risk

Hi Risk

N/A

Hi

So

Lo

Pre Appraisal

Key Risks to EOR developments in Field F

6

Targeted Appraisal Campaign

Key Technical

risks identified

Gradio

Interference testing

Analogue studies

Air

Brine

Formation water

F-3 F-2 F-5 F-6

GR GR GR GR

Gradio Surveys

Air column 50-100 m

Foreign fluid (brine) in F-2,3 and 5

Formation water in F-2,5,6

No Oil column was observed

=> Water-filled fracture network likely

F-1

F-3 F10

F-9

F-8

F-7

Field F

Field D

F-10 total losses while drilling

(interference with 4 wells):

F-2,3,7,8

F-10/F-2 max. Keff= 700 md

F-10/F-3 max. Keff= 700 md

F-3/F-2

Interference:

Max. Keff: 300 md

Interference Testing

Connected network of faults and fracture corridors

Very low fracture permeability (~500mD)

Main Boundary Fault non-sealing

F-2

Direct pressure

communication across

the Main Boundary Fault

F-10

Natih

Natih

F-8

No vertical exaggeration

Shuaiba

F-3

4000

4050

4100

4150

4200

4250

4300

4350

4400

7-J

an-1

1

17-J

an-1

1

27-J

an-1

1

6-F

eb

-11

16-F

eb

-11

26-F

eb

-11

8-M

ar-1

1

18-M

ar-1

1

Pre

ssu

re (

kP

a)

Date

Effect of AGS10 Total Losses

AGS8 AGS3 AGS2

F-2

F-8

F-3

Drilling with

losses in F-10 Acid induced

losses F-9

Pre

ssu

re (

kP

a)

Main Boundary Fault Non-Sealing

F-9 total losses after acid job was

observed in F-3 and F-8

F-8

F-3 F-9

F-10

F-9

Gauge

Packer

Inject

Bottom-Seal Capacity of Hawar

Special interference testing set-up to test seal capacity of

Hawar

Delayed signal arrival in Kharaib

Hawar

Sh

ua

iba

Fracture corridor Spacing ~300 to 400m

Background Fractures

Fracture corridor

Permeability 300

to 700mD

Water-filled

Frequency

‘Length’

weighted

Fracture Corridor Orientation (N=27)

Conceptual Fracture Model from New Data Acquired

Conceptual Fracture model developed to explain the static and

dynamic observation (wells, seismic Interefence testing, drilling)

Connected Fracture corridors with isolated background

fractures

Fracture appear

water filled –

only water

produced cold

Gradio surveys

show no oil-in

from fractures in

12 months

Extended Cold

production:

only water

Direct

pressure

communicatio

n across fault

No analogue

for Hawar as

pressure seal

Total losses

across major

fracture zones

Lateral

interference

signal

Observed

spacing much

larger than

field A

Only one major

fracture set; low

frac. perm

~500mD

Total losses in F-

7 – fracture

corridors

continue to mid

flank

Detailed fracture

spacing analysis

and comparison

with all fields in

GSB

Only water produced in all (5) well tests

Plugs show

<20mD; avg

3mD

Can match F-1

build-up with <

5mD matrix rel.

perm

Leaching-prone

rudist facies

missing in F

Calculated log saturations confirmed

by Dean Stark Measurements

Increase in likelihood of risk

materialising

Risk evolution with new data and study work

Risk/Opp

Fault

Leak

Base

seal leak

Fracture

Density

Mobile

water

Low

matrix

perm

Sat. Oil

Water

supply

and

disposal

SA

GO

GD

A

lt T

he

rma

l

ISC

C

he

mic

al

Post Appraisal Pre Appraisal

Hi Risk

Opportunity

per Recovery

Process N/A

Fault

leaking

Base seal breached

by major fracs –

spacing under

analysis

Too sparse for

GOGD but pos.

OK for chemical

Mobile water

(in matrix also)

Incr. risk low

matrix perm

Evolution of Risks with Appraisal

Risk/Opp

1 Fault

Leak

2

Base

Seal

Leak

3 Fracture

Density

4 Mobile

Water

5

Low

Matrix

Perm

6 Sat. Oil

7

Water

Supply

and

Disposal

SA

GO

GD

A

lt T

he

rma

l

ISC

C

hem

ica

l

Ran

k

1

7

5

4

3

2

6

Conclusions

In field F approach demonstrated to be effective for rapid appraisal that should be

applied to other discoveries entering the maturation funnel

In the case of field F, a fast-pace maturation campaign was executed & key risks

for thermal developments have materialised:

Seal: fault leak, water-filled fracture system =>breached accumulation

Reservoir: matrix blocksize too large, fracture & matrix permeability too low

Saturation too low, reservoir too thin, oil viscosity too high => Heating efficiency

too low

Novel-chemical flooding techniques might provide a way to unlock other heavy-oil

accumulations in carbonates. They are further evaluated for field F.

Dynamic data are critical to characterize fracture networks. Total losses during a

drilling operation are a good signal for interference testing

Petroleum Development Oman

Analogues Methodology

Extensive research has been carried out to find analogues for F

Analysis of general energy measures for steam projects

Data base & literature research for heavy all heavy oil developments (SPE, CC

data base, Oil & Gas Journal)

Scanning of field data from the heavy-oil Carbonate provinces (Middle East,

Europe, Canada, Mexico)

Numerical Fracture model Integrating All Data

Large areas without connected fractures

Probabilistic Screening of Subsurface Scenarios

Scenario Definition

Boundary Fault

Base Seal/ Fracture spacing

Fracture orientation

Rock Leaching upper Flow Unit

Water Mobility Sw

No Seal (0.9) 10 m Cr(0.2) Fl(0.05)

DIP parallel & Fault parallel Cr (0.35), Fl (0.8)

No leaching (0.75) Sw < 0.3 Cr (0.8) Fl (0.3)

Seal (0.1) 40 m Cr(0.5) Fl(0.35)

DIP parallel Cr (0.65), Fl (0.2)

Patchy leaching (0.2)

Sw > 0.3 Cr (0.2), Fl (0.7)

400 m Cr(0.3) Fl(0.6)

Extensive leaching (0.05) P

ossib

le O

utc

om

es

Key Subsurface properties

Development options Showstopper – ‘Technology’ Commercial showstopper SA-GOGD Boundary Fault not sealing and sparse

fracture spacing (>40 m) and low fracture permeability

Energy efficiency

CSS Very slow process, low recovery

Steam Drive Fracture Spacing < 400 m Energy efficiency, challenging in low permeability environment

TA-WOGD (hot water) - Very slow process

SAGD Low matrix permeability

ISC Boundary Fault not sealing, effective fracture permeability <1D and fracture spacing >10 m

Chemical drive Lack of Base Seal (Fracture Spacing < 400 m)

Low injectivity, slow process

EOR Options and Showstoppers

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

SAGOGD CSS Steam Drive SAGD ISC (quasi

SAGOGD)

Solvent Drive Solvent Ass.

GOGD

TAWOGD

Crest Flank

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

SAGOGD CSS Steam Drive SAGD ISC (quasi

SAGOGD)

Solvent Drive Solvent Ass.

GOGD

TAWOGD

Crest Flank

Chemical

Drive

Probabilistic Screening of Subsurface Scenarios

Results

Probabilistic score per recovery method for both crest and flank

Zero score: at least one technical showstopper in all subsurface

combinations

Only CSS, steam drive, hot water oil gravity drainage (TAWOGD)

novel-chemical drive appear technically possible

Petroleum Development Oman

The Authors thank

Petroleum Development Oman

and

Sultanate of Oman Ministry of Oil and Gas

for permission to present this work

Acknowledgements

Warrlich, GEO12