TELFORD FIELDBACK TO BASICS: INTEGRATION OF DATA AND CONCEPTUAL

MODELING UNDERPINS SUCCESSFUL RE-DEVELOPMENT OF A

COMPOSITIONAL BROWNFIELD

OUTLINE

– Overview

– Integration of Static/Dynamic data to understand F5 production well anomalous water-cut

– Feedback loop (back-to-basics) into dynamic data and water chemistry to explain anomalous and unmatched F5 water cut

– F5 Intervention and Results

– Conclusions

2

Partnership: NexenCNOOC Limited: 80.41%

Apache Corporation: 15.65%

Maersk Oil: 2.36%

Premier Oil: 1.59%

3

Upper Piper

Lower Scott

Upper Scott

Reservoir: Upper Jurassic shallow-marine – KPT, Piper &

Scott Sands

Hydrocarbon: Volatile Oil/Rich Gas Condensate

Development: Phased Development

East: Water flood: 6 producers and 1 injector

West: Depletion

Marmion: Water flood

Facility: Subsea tie-back to Scott Facilities

,

TELFORD FIELD KEY FACTS

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15/22-G1z

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15/22-13

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15/22-17z

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15/22-2

15/22-20

15/22-F315/22-F3z 15/22-F5

15/22-G1

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15/22-G3

15/21a-4415/22-F1

15/22-F215/22-F415/22-J36y

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Depth

Symbol legend

fault_polygons for mapping Oil Injection water Condensate Dual completion oil Drilling well Undefined

Country

Block

License

Model name

Horizon name

Scale

Contour inc

User name

Date

SignatureCopy of 2011_Jan_DOW_STRIKE_DC

KPT

1:40000

100

akinkuna

05/09/2012

Map

TELFORD KPT TOP STRUCTURE MAP

A A’KPT: Kimmeridge-Piper-Transition, UP: Upper Piper,

US: Upper Scott, MS: Mid Shale, LS: Lower Scott, S: Saltire

Type Log: 15/22-F3z

KPT

UP

US

LS

S

MS

F5/

WEST TELFORD CONTEXTUAL INFORMATION

4

15/22-F3z

• 12.4 MMboe production. Shut in 2004

• Re-opened Feb 2013: 5400 bopd/11.5MMscfd, ~63% WC

15/22-F5

• Lower Scott isolated at 3000 bopd/2 MMscfd , 75% WC prior

to producing from Upper Piper

• Upper Piper produced 1.8 MMboe. Shut in 2007

• F5 tested Oct 2012: ~350 bopd/1MMscfd, 0% water cut

• Unable to sustain flow: damaged or low reservoir pressure?

6

15/22-F3z

•Upper Piper Produced ~12 MMboe prior to shut in in 2007

due to low reservoir pressure and high water cut

•Re-opened Feb 2013: 5400 bopd/11.5MMscfd, ~60% WC

15/22-F5

•Lower Scott isolated at 3000 bopd/2 MMscfd , 75% WC prior to

producing from Upper Piper

• Upper Piper shut in 2007 at ~ 3000 Bopd/3 MMscfd, 75% WC

•Upper Piper tested Oct 2012: ~350 bopd/1MMscfd, 0% WC

• Unable to sustain flow: damaged or low reservoir pressure?

PROBLEM SUMMARY

Lower Scott Upper Piper

Why did the F5 produce at high water

cut when the F3z down-dip produced at

lower water cut?

Ga

s R

ate

(c

f/d

)

Oil R

ate

(b

op

d)

Wate

r cu

t

DH

G p

ressu

re (

psia

)

7Fault baffling but some degree of pressure communication. Given F3z still produced oil downdip

WEST TELFORDCOMPARTMENTALIZATION / BAFFLING EVIDENCE

• Although the general trends for both wells are

similar, significant drawdown (>1000 psi)

periods in F5 show little or no noticeable

response in F3z BHP

• Suggests very significant baffle(s) in between

both wells??

All pressures normalized to gauge depth 9860 ftss

F3z pressure higher

by 120 – 250 psi

Ps

ia

• History matched MBAL model(s) prior to simulation modeling helped underpin

the HCIIP estimates.

• All history matched models required 108.87 MMrb of HC fluid (with varying

proportions of gas and oil) to honour the tank pressure (SIBHP) data.

COMPOSITIONAL GRADIENT AND RFT(NEAR CRITICAL FLUIDS)

8

CONCEPTUAL MODELLINGINITIAL CONDITIONS (1997)

99

F3Z(Sep 97)

F3(Nov-96)

0.246 psi/ft

KPT/UP

US

LS

0.155 psi/ft

0.145 psi/ft

0.178 psi/ft

Dew point fluid

Bubble point fluid

Bubble point fluid

Phase Envelope based on

reservoir fluid composition only

Fluid gradients based on RFT

Fluid PVT complements RFT data.

1

2

3

0.45 psi/ft

F5 HISTORY AND FORECAST

10

• A high perm streak from aquifer failed to match the water cut in F5 Piper zone.

• The structural evaluation precluded a Upper Piper being juxtaposed against Marmion. Even after

adding artificial connections and reducing the reservoir volume in Marmion, we were still unable to

match the water production observed in F5 Upper Piper

• A model with cross-flow from Scott to Piper showed a good match to Piper water cut – suggesting

that this mechanism is highly likely.

• Re evaluated produced water chemistry data in conjunction with production data

Able to match pressure data but not water production. Various scenarios tried

Simulation

data

Observed

data

Pressure

Simulation

data

Observed

data

Water cut

Mbal, PVT and production data incorporated into a simulation model

11

0

5000

10000

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20000

25000

30000

35000

40000

45000

50000

F3z Upper Piper rate vs cumm

F5 Upper Piper rate vs cumm

RATE VS. CUMULATIVE HYDROCARBON PRODUCTIONCOMPARISON OF F5 VS. F3Z UPPER PIPER

Gradual decline after

~ 9 MMboe production

Rapid decline after ~1.5 MMboe

When well is higher on structure and

expected to produce dry for a longer

period

• F3z and F5 pressures indicate

they are in communication

• No reason for F5 to show the

observed rapid decline

Ra

te (

bo

e)

Cummulative (boe)

1

2

0.046

0

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DRAWDOWN ACROSS BRIDGE PLUG

WATER CUT

Pre

ssu

re d

iffe

ren

tial acro

ss p

lug

(p

si)

F5 WELL: DRAW DOWN ACROSS BRIDGE PLUG ISOLATING LOWER SCOTT FROM UPPER PIPER

***This Assume Lower Scott is at a constant reservoir pressure of 3200 psi when isolated. The Lower Scott should have continued

to build up reservoir pressure after initial isolation and the differential seen by the bridge plug could have been significantly higher

Beginning of leak

when differential

begins to develop

leak accelerates as differential

increases to 500 psi and

corresponds to jump in water

cut from <10% to >75%

Evaluation suggests

this is the true WC

(< 5%) of the Upper

Piper Formation

Water

WC rises up to ~ 70-

80% (rapid timing not

observed in any other

wells) Water cut shows

decline in barium

(due to sulphates in

sea water?)

UP

LS

CONSEQUENCES OF LEAK: F5 WELL BORE DAMAGE

13

• Sharp rise in fluid rate

(purple line A to B)

• Increase in WC

• Indicating a mechanical

failure

• Reservoir pressure declines rapidly at well

opening (C)

• But builds immediately back at shut in (D)

• At each opening, the total fluid rate

continues to decline despite increasing

reservoir pressure (E)

This is an indication of well bore

damage and not reservoir

productivity. It suggest a

progressive damage as well

continues to build up scale

ca 2cm

A

B

C

D

E

Scaling observed in nearby well

Ga

s R

ate

(c

f/d

)

Cummulative (boe)

Oil R

ate

(b

op

d)

Wa

ter

cu

t

DH

G p

res

su

re (

ps

ia)

14

F2 (projected 240m NE along dip)

• Injection into all zones.

• No PLT’s to determine split

F5 drilled (Feb 2005) as a twin well to F3 (Nov 96)

• Upper Piper was found to be ~1350 psi depleted relative to F3 RFT

• Explained by 12 MMboe produced from F3z

• Lower Scott was found to be ~500 psi over-pressured relative to

F3 RFT

• Explained by fault breakdown due to F2 Upper Piper injection and

juxtaposition of Marmion Upper Piper against West Telford Lower

Scott

Marmion

West Telford

KPT/Upper

Piper

Upper

ScottLower

ScottInjection into Marmion

Upper Piper breaches

fault and over-pressures

Lower Scott in West

Telford

F3z (projected 1.3 km SE along strike)

Upper Piper production depletes

pressure

F5

F2

NW

SE

F3z

SECTION THROUGH WEST TELFORD MARMIONSHOWING PATH OF WATER TO F5 UPPER PIPER PERFORATIONS

F5 INTERVENTION SUMMARY

15

• The intervention encountered significant

amounts of Barium Sulphate scale over the

Piper perforations.

• The scaling was only across the Upper Piper

perforations, suggesting the point of mixing

was at base of the Upper Piper and seawater

was from below

• The original Bridge Plug failed to isolate the

Lower Scott from Upper Piper, allowing the

Lower Scott, which was the source of

seawater to mix in the well at the Upper Piper

perforations, permitting the formation of the

Barium Sulphate scale.

• The Upper Piper produced during the clean-

up at very low water cut, with no evidence of

sea-water

• Production test: ~22,700 boe/d (12,700 bopd,

60 MMscfd), <2% water cut

Sc

ale

No

sc

ale

PRODUCTION PLOT OF F5PRE AND POST WELL INTERVENTION

16

Oil (

bo

pd

)

Gas (

scf/

d)

Pre-intervention: 1500 bopd/6.6 MMscfd……>50% BSW

Post intervention: 11,500 bopd/40 MMscfd…….0% BSW

CONCLUSIONS

• Integration of dynamic data to build conceptual model enhanced our understanding of the near-critical fluid reservoirs with compositional gradient.

• Conceptual model allowed us to build a fit for purpose simulation model. History matching MBAL model(s) helped underpin the HCIIP range.

• Multi-disciplinary approach is the key to good history matching and success.

• The source of water production in the F5 Upper Piper was narrowed down to water influx via Marmion and a leaking bridge plug in the well

• Integrated project work helped the team to see risks early in the project phase and plan for risk mitigation strategies.

• F5 well now restored to dry production

• If you don’t know why your well stopped producing……..please revisit it!!

17

ACKNOWLEDGEMENTS

• Telford Field Partners who have given permission to publish this work

– Apache Corporation

– Maersk Oil

– Premier Oil

• NEXENCNOOC Integrated team

– Liz Ross

– Devinder Arora

– Akinyemi Akinkunmi

– Francis Boundy

– Olumide Akinsanmi

– Frank Davis

– Ahmet Tunoglu

– Andrew Legge

– Mohammed Mobasheri

– Alan Barrack

18