chasing hidden potential by 2g & r synthesis using … · 2018. 5. 30. · gdt lb+c @ 4311m odt...

CHASING HIDDEN POTENTIAL BY 2G & R

SYNTHESIS USING OBN DATA IN THE

ALWYN NORTH FIELD

Arindam Mitra, Ali Parsa, Onyeka Onyia,

Johann Frangeul & Kevin Jones

Total E&P UK

OUTLINE

Alwyn North OBN –15th DEVEX Conference & Exhibition – Aberdeen, 2018 2

● Introduction to field

● Imaging improvement of OBN over Vintage

● 2G & R approach : Inversion & Reservoir Characterization

- OBN Elastic Inversion results

- Reservoir characterisation

- Comparison with Static data

● Triassic Production overview

● Integrated workflow / methodology for resource estimation

● Summary & Conclusions

● Acknowledgement

Macbeth

BCU

Brent

Dunlin

Statfjord

Trias

Trias D

Lomvi

W E

ALWYN NORTH: INTRODUCTION & DESCRIPTION


● Discovered in 1975 in Northern North Sea UK (blocks 3/9 & 3/4), on production since 1987

● Eroded and tilted fault blocks, separate HC pools within Jurassic & Triassic

● Actual Average Production ~ 10 kboed

● Cum. Prod. = 618 Mboe

● 3 developed reservoirs:

- Brent (RF-50%) → Blowdown phase with CGL activation

- Statfjord (RF-60%) → Gas pool with PWRI

- Triassic (RF-18%) → Future drilling target focused on Triassic

● Total 4 seismic acquisitions : 1981/1996/2001 Streamer, 2014 OBN

Top Triassic Depth Map

ALWYN NORTH TRIASSIC STRATIGRAPHY


•Sub divided to 5 zones : A, UB, LB, C & D

• LB and C are the most prolific

Low NTG → Channel & sheet sands deposited in a semi-arid alluvial plain

Vertical heterogeneity observed at production time scales

Common static pressure gradient in LB and C zones

Gas in A, UB, LB and C; Oil in D

100m

Intra Formational Seal

Not Modelled

C1

C2

C3

C4

LB1

LB2

LB3

LB4

LB5

LB6

UB1

UB2

UB3

UB4

A1

A2

A3

NTG: 0.36

PHIE: 0.1

NTG: 0.30

PHIE: 0.11

NTG: 0.21

PHIE: 0.10

NTG: 0.18

PHIE: 0.09

NTG: 0.25

PHIE: 0.1

ALWYN NORTH INITIAL PRESSURE & FLUIDS


No water encountered nor produced by Triassic Main panel wells

Lower B + C layers gas column in same initial trend

A (gas) and D (oil) layers in different trends

Initial Pressure = 585 bars @ 3900 mTVDSS

3500

3700

3900

4100

4300

4500

510 520 530 540 550 560 570 580 590 600 610

m T

VD

SS

Pressure (bara)

ABC sands virgin pressure

3-10b-2 C

N21-A

N33-A3

N33-UB4

N33-UB3

N33-UB1

N33-LB6

N33-LB5

N33-LB3

N33-LB1

N33-C2

N33-C1

N34-UB4

N34-LB5

N34-LB3

N34-LB2

N34-C2

N35-A2

N35-A1

N35-UB4

N35-LB5

N35-LB4

N35-LB3

N35-LB2

N35-C3

N35-C2

N35-C1

N38-UB4

N38-LB5

N38-LB2

N49-A2

N49-UB4

N49-LB3

3-9a-11 A3

3-9a-11 UB3

3-9a-11 LB4

Water

N49-Statfjord

D

Triassic South

3/9a-11

Triassic Main

LB + C

Triassic Main

A

Triassic Main

Multi-layer D

Triassic West (N49)

Aquifer

Statfjord West (N49)

Aquifer

GDTLB+C @ 4311m

ODTD @ 4534m

3500

3700

3900

4100

4300

4500

1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500

m T

VD

SS

Pseudo-Potential (m)

ABC sands before production

3-10b-2 C

N21-A

N33-A3

N33-UB4

N33-UB3

N33-UB1

N33-LB6

N33-LB5

N33-LB3

N33-LB1

N33-C2

N33-C1

N34-UB4

N34-LB5

N34-LB3

N34-LB2

N34-C2

N35-A2

N35-A1

N35-UB4

N35-LB5

N35-LB4

N35-LB3

N35-LB2

N35-C3

N35-C2

N35-C1

N38-UB4

N38-LB5

N38-LB2

3-9a-11 A3

3-9a-11 UB3

3-9a-11 LB4

N49 A2

N49 UB4

N49 LB3

D

Triassic Main

A Triassic South

3/9a-11

Triassic Main

LB + C

Triassic Main

Multi-layer DTriassic West (N49)

Aquifer

GDTLB+C @ 4311m

ODTD @ 4534m

Pressure (bars)

De

pth

(m

TV

DS

S)

Pseudo-Potential (m)

De

pth

(m

TV

DS

S)

SEISMIC DATA QUALITY COMPARISON

Alwyn North OBN –15th DEVEX Conference & Exhibition – Aberdeen, 2018

Vintage Streamer

Full Stack Near Stack

Far StackMid Stack


6

BCU

Dunlin

Statfjord

Trias

Lomvi

Macbeth

Brent

Trias D

SEISMIC DATA QUALITY COMPARISON

OBN -PP

Full Stack Near Stack

Far StackMid Stack

BCU

Dunlin

Statfjord

Trias

Lomvi

Macbeth

Brent


Trias D

Improved Imaging (at all levels including deep) & quality of angle stacks.

Broader Bandwidth & Higher Signal/Noise ratio.


7

METHODOLOGY: INVERSION & RESERVOIR CHARACTERIZATION


Output of

IP/PR

Cubes

Inversion

Processing

output : Angle

Stacks

Structural

Interpretation

Inversion result

QC/analysis

IP-PR Cross Plot

analysis :

Inversion & wells

PDF computation

for 3 zones : A&UB,

LB & C

Property Cubes

(Sand

probabilility,

PseudoPHIE)

Results cross-validated

against well & dynamic data

8

N35

Trias

Trias D

Base

LVS

OBN INVERSION QC : EXAMPLE N35


OBN Inversion

Upscaled Well logs

Fine-Scale Well Logs

Inversion results QC’d in

details for all 15 Triassic

wells. Globally good to

moderate match with well

results. Reasons for areas

of poor match well

understood.

Inversion quality indicator

0.7

1

GR PHIE Ip Vp/Vs MarkerIp Vp/Vs

● 2 areas of seismic artefacts:

1. Close to crest / Main Bounding Fault

(MBF).

2. Close to major faults.

● Higher impact in Shallow (A&UB),

smallest impact in deep (C1/C2).

WHERE CAN WE TRUST SEISMIC RESPONSE ?

10

Wells unaffected by artefacts

Wells affected by identified

artefacts

Trias A/UB Trias LB4/5/6 Trias LB1/2/3 Trias C1/2


Areas affected by artefacts

W ECombined Sand Probability

Weakening impact of seismic artefact with depth

IP - PR CROSSPLOTS : WELLS / OBN INVERSION


0.02

PO

RO

SIT

Y

Trias A & UB with BEST wells

IP

PR

Trias C

IP

Trias C

IPP

RP

R

Band Limited Inversion

Trias LB

IPP

R

Upscaled Well Logs

Trias LB

IP

Trias A & UB

PR

IP

PR

IPP

R

0.08

Non reservoir

Porous

Sand

Good confidence in LB and C layers. Poor confidence in A/UB layers.

STATIC CROSS-VALIDATION


3/9a-N35

BCU

Statfjord

Trias

Trias D

A A’

Base

LVS

LB3

C4

C2

3/9a-N35

GR PHIEPseudo

PHIEMarker

Sand

Proba

Upscaled

PHIE

Pseudo PHIE & Probability of

Sand Cube, with Upscaled

PHIE log along well

0100

A

UB

LB4/5/6

LB1/2/3

C3/4

C1/2

Sand resolved

Sand partly seen

Sand not seen

A

A’

12


28

Ip:Fine &

Upscaled

Globally over 15 wells, better match for C

& LB, poor match for A/UB → Key factors :

thickness beyond resolution & artefacts

Layers Sands seen

on Inversion

Weak

Inversion

response

Sands not seen

on Inversion

A 7% 7% 86%

UB 20% 7% 73%

LB4/5/6 60% 20% 20%

LB1/2/3 33% 20% 47%

C1/C2 36% 36% 28%

Inv Ip Inv PR

TRIASSIC PRODUCTION OVERVIEW


2.5GSm3

1.0GSm3

0.1GSm3

Cum Gas Prod

(GSM3)

Average Cumulative Production = 7.8 Mboe

Production Mechanism = Depletion

43% of Cum prod came from N33 & N35

Main producers located at the crest

Down-dip wells (N44, N46, N47) impacted by depletion

N43

N42

N35

N47

N51Z

N40

N38

N34

N44N41

N33

N46

N39

N48

1996 97 98 99 2000 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 160.0

0.5

1.0

1.5

2.0

2.5

Date

Monthly Cum Gas (Bscm)

Completion 3/9a-N33

Completion 3/9a-N34

Completion 3/9a-N35

Completion 3/9a-N38

Completion 3/9a-N39

Completion 3/9a-N40

Completion 3/9a-N41

Completion 3/9a-N42

Completion 3/9a-N43

Completion 3/9a-N44

Completion 3/9a-N46

Completion 3/9a-N47

Completion 3/9a-N48

Completion 3/9a-N51Z

Cu

m G

as P

rod

ucti

on

( G

Sm

3)

0.5

1.0

1.5

2.0

2.5 N35: 22Mboe

N33: 21Mboe

N41: 13.5Mboe

N42: 9Mboe

N39: 8.4 Mboe

N38: 7.7 Mboe

N40: 6.4 MboeN44: 5.7 MboeN43: 5.3 Mboe

N47: 3.9 Mboe

N51z: 3.6 Mboe

N46: 0.9 MboeN48: 0.3 Mboe

N34: 1.4 Mboe

Triassic Cumulative Production

10.9 GSm3 (~110Mboe)


N35 (RFT): 586

N38(RFT): 553N40 (RFT):563

N42(RFT): 335

N43(RFT): 506

N47(RFT):303

050

100150200250300350400450500550600650

1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 2017SIP

pre

ss

ure

(b

ars

) @

Da

tum

39

00

TV

DS

S

Date

C1 Sand North

N35 C1 sand N38 C1 Sand

N40 C1 sand N42 C1 sand

N43 C1 sand N47 C1 sand

DYNAMIC ANALYSIS

3500

4000

4500

5000

5500

6000

250 350 450 550 650

TVD

SS, m

Pressure, bar

Triassic RFT C1 sands (North wells)

N35-07/1997

N38-08/1998

N40-05/2000

N42-07/2001

N43-12/2001

N47-06/2003

Connected

Volume per layer

1.8GSm3N44: 0.01GSm3

N34< 0.01GSm3

N39: 0.03GSm3

N48

N39

N46

N44

N33

N41

N34

N38

N40N51

N35

N47

C1 : 2GSm3

N44: 0.01GSm3

N35: 1.1GSm3

N34

N38

N40

N51

N35

N47

N43

N42

N38:0.8GSm3

N40:0.1GSm3

N35: 1.1GSm3

N34

C1 connected area from

dynamic data

Communication

map

N35

N38

SIP analysis

Production split per layer

N34

N38

N40

N51

N35

N47

N43

N42

N o Sand

P o o r (Φ<10%)

M edium(10<Φ<20% , 0.5<K<50mD )

Go o d (Φ>20% , K>50mD )

Sand

properties

and presence

1.

2.

3.

0

50

100

150

200

250

300

350

400

450

500

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

P/Z

Ultimate Gas Production , GSm3

N35 - C1 sand

C1

P/Z per well per layer

WFT analysis per layer

PLT analysis

SIP analysis per layer from PLT

N48

N39

N46

N44

N33

N41

N34

N38

N40N51

N35

N47

N44: 0.01GSm3

N34: 0.01GSm3

N39: 0.4GSm3

N33:1.2 GSm3

X

LB5(S): 1.2GSm3

LB5(S) RF: 56%

RFT Communication

SIP Communication

Connected Volume (P/z)

Sand extension from OBN

U

U

U

L

LB5-L (N): 0.35GSm3

N38

N40

N51

N35

N47

N43

N42

RFT Communication

SIP Communication



LB5-L(N) RF: 90%

L

L

L

U

UU

LB5-U(N): 0.8GSm3

LB5-U(N) RF: 82%

U

N44:0.52 GSm3

N48

N39

N46

N44

N33

N41

N34

N38

N40N51

N35

N47

LB4 (S): 0.52GSm3

LB4(S) RF: 41%

RFT Communication

SIP Communication



LB4 (N): 1.09GSm3

N35:0.77GSm3

N38

N40

N51

N35

N47

N43

N42

N47:0.3GSm3

RFT Communication

SIP Communication



LB4(N) RF: 67%

U

U

U


LB4

LB4/LB5/LB6 SAND CONNECTED VOLUME

LB4/LB5/LB6 sand probability map

LB5

LB6

LB4

LB5-upper

LB5-lower

Polygon areas are based

on connected GIP per

layer from dynamic

synthesis

Sand probability map

used as a guide to locate

the polygons trying also

to respect the well

communication maps

Good agreement

between seismic and

dynamic for LB4/LB5

layers in the North

Agreement more

difficult to find in the

South due to poorer

sand imaging (Not

adequately stacked)

DYNAMIC CROSS-VALIDATION – LB4 /LB5 /LB6 SANDS


Dynamic Connectivity

16

Well2

Well1

LB5

LB6

LB4

Sand Probability

@45% cut off

Area : 6.93 Sq Km.

Avg. Petro:

Net sand: 29.3m

PHIE: 0.105

SWE: 0.530

● Seismic delineates

LB4/5/6 sands when

adequately stacked.

● IGIP from seismic is

slightly higher but

● LB6 has no connected

volume from dynamic

data

● Very high recovery

factors observed in

LB4/LB5 → Dynamic

Connected volume

under-estimated ?

● IGIP from seismic inline

with connected gas

volume.

● Good confidence to

identify LB4/5/6 sands

in main panel North →

helps to validate sand

presence in Well 1

IGIP – 2.9 GSm3 Connected GIP – 2.3 GSm3

N43

N35

N51ZN47

N42

N40

INFILL TARGET RESOURCES


Well 1

Trias

Trias D

A A’

Base

LVS

LB3

C4

C2

Well1Pseudo

PHIE MarkerSand

Proba

INTEGRATED Probability of Sand Cube - Output

from Caress PDF & Combined together

0100

A

&

UB

LB4/5/6

LB1/2/3

C3/4

C1/2

A

A’

A/UB

Dunlin

Use of Analogue

Use of Seismic

Use of Seismic

Primary targets – LB sands

Statfjord

Use of Analogue

Use of Analogue


Well1 Pseudo

PHIE MarkerSand

Proba

0100

A

&

UB

LB4/5/6

LB1/2/3

C3/4

C1/2

Use of Analogue

Use of Seismic

Use of Seismic

Use of Analogue

Use of Analogue

Only wells with perforated intervals

and PLT data are included

WELL 1 RANGE OF RECOVERY WITH ANALOGUES

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.50

.00

0.0

5

0.1

0

0.1

5

0.2

0

0.2

5

0.3

0

0.3

5

0.4

0

0.4

5

0.5

0

0.5

5

0.6

0

0.6

5

Fre

qu

en

cy

Connected Vol.(GSm3) Class

A+UB histogram

A+UB

1C

2C 3C

0.0

0.5

1.0

1.5

2.0

2.5

0.0

0

0.0

1

0.0

2

0.0

3

0.0

4

0.0

5

0.0

6

0.0

7

0.0

8

0.0

9

0.1

0

0.1

1

0.1

2

0.1

3

0.1

4

0.1

5

Fre

qu

en

cy


C3/C4 histogram

C3/C4

1C 2C

3C

0.00.51.01.52.02.53.03.54.04.5

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

Fre

qu

en

cy


C1/C2 histogram

C1/C2

1C/2C

3C


WELL 1 RESOURCES: RECOVERY FACTOR ASSUMPTIONS

1. Surface area from seismic : LB4/5/6 & LB1/2/3

● Uniform distribution with parameters

● Min: 0.3

● Max: 0.7

2. From analogues: A/UB + C1/C2

+ C3/C4 :

● RF range is higher as the

volume is smaller than LB

layers then less likely to be

depleted

● Uniform distribution with

parameters

● Min: 0.5

● Max: 0.7

N33

N35

N38N39

N40

N41

N42

N44

N46

N47

N48

N51z

N34

TRN 1C

TRN 2C

TRN 3C

0

0.5

1

1.5

2

2.5

3

0 1000 2000 3000 4000 5000 6000 7000

Cu

m P

rod

, G

Sm3

Days on Production, days

Triassic Main + TRN Resources

N33

N35

N38

N39

N40

N41

N42

N43

N44

N46

N47

N48

N51z

N34

TRN 1C

TRN 2C

TRN 3C

3C2C1C

Pro

ba

bil

ity

0

50

100

150

200

250

300

350

400

450

500

0.0 0.5 1.0 1.5 2.0

P/Z

Ultimate Gas Production , GSm3

TRN P10 RFTRN

Gp

RF : 33%

TRN 1C RF

SUMMARY & CONCLUSIONS :


● OBN provided a step change improvement in image quality, leading to improved reservoir

characterisation, consistent with global geological understanding and dynamic synthesis of Triassic.

● Good confidence on the ability of the PP Elastic Inversion to predict stacked porous sands.

● Imaging / inversion uncertainty & limitation :

- Close to the crest due to BCU erosion

- Close to big faults due to strong fault plane reflection

● Adapted workflow managed to establish correlations between inversion & well results. Confidence in

seismic :

- HIGH : C1/C2 in Main panel (both North & South) & LB4/5/6 in Main-Northern panel

- LOW : LB1/2/3 in the Main panel (both North & South) but good response in Well 1 panel

- NO : for A/UB layers

● Gas in Place Volume estimated from the seismic is considered as minimum connected gas volume

● Confidence gained in main panel helps to predict sand presence towards potential future target & it’s

resource estimation.

20

ACKNOWLEDGEMENT


● Total E & P UK – For allowing this work to be published in DEVEX.

● CGG – for their dedications & efforts in OBN processing & Inversion.

● Our colleagues from Total :

- Anne-Sophie Barnola, Jesse Clark, Karim Ouragh, Gregory Fontaine, Romain Rebut, Anthony

Douillard, Perry Pogue, Joffrey Brunellière, Saverio Sioni, Michel Erbetta, Matthew Rowlands,

Xiaolin Lu, Tom Blanchard, Richard Ward, Steinar-R Kvinnsland, Jose Luis Megchun-Rivera, Eoin

McManus, Hannah Cumming, Bill Christie, Richard Lembard and Jean-Luc Piazza.

21

chasing hidden potential by 2g & r synthesis using … · 2018. 5. 30. · gdt lb+c @ 4311m odt...

Documents