Gas lift challenges in NS TAQA’s perspectives · Gas lift challenges in NS –TAQA’s perspectives Charles Adoga, Snr Production Engineer, TAQA Europe June 2018 SPE European Artificial

Gas lift challenges in NS – TAQA’s perspectives

Charles Adoga, Snr Production Engineer, TAQA Europe

June 2018 SPE European Artificial Lift Conference 2018 1

Agenda

• Introduction

• GL operation, design envelope & optimisation

• GL operations out-with design envelope

• WH barrier envelope impact on GL Operation

• GL - production add & enhancement lever

• Summary


Introduction


100% - Tern Alpha

70% - Corm Alpha

Cormorant Alpha Subsea well

• Well completed and online Aug 11

• GL design parameters for the life cycle of well

• Design CHP 120 bar

• Valve pressures = f(T)

• Gas Lift commissioned in Dec 11


GL operation and design envelope 1


20

40

60

80

100

120

1401

8/A

pr/

12

07

/Ju

n/1

2

27

/Ju

l/1

2

15

/Sep

/12

04

/No

v/1

2

24

/Dec

/12

CH

P b

arg,

gl c

hk

%, W

HP

bar

g, W

HT

de

g C

Ann P WHT Opening P Operating P Csg P

Max design csg P

Valve opening P

orifice operating P

Erratic

WHT

CHP >

Design


1 YR

0

20

40

60

80

100

120

140Ja

n/1

4

Feb

/14

Ap

r/1

4

May

/14

Jul/

14

Sep

/14

Oct

/14

Dec

/14

CH

P b

arg,

gl c

hk

%, W

HP

bar

g, W

HT

de

g C

Ann P WHT Opening P Operating P gl Chk Csg P


Max design csg P

Valve opening P

orifice operating P

stable

WHT

CHP <

design

CHP>design


1 YR


• Gas lift commissioned at CHP > design

• Well operated with CHP > design most of the time

• Tubing to A-annulus communication

• Well require regular A-annulus unloading

Lesson – It is poor operating practice to continuously operate the CHP above the valves opening pressures.




• DHPG and gas lift meter on well had failed

• Reducing CHP was recommended using WHT proxy

• This is challenging previously entrained practice


GL operation and optimisation 1


0

100

200

300

400

500

600

0

20

40

60

80

100

120

140

Gl R

ate

(K

sm3

/d)

CH

P b

arg,

gl c

hk

%, W

HP

bar

g, W

HT

de

g C

Ann P WHT Opening P Operating P gl Chk Csg P gl Rate

Stable WHT

CHP < design

GL CHK 50% to 7%


2% field production increase

0

200

400

600

800

1000

1200

1400

0

20

40

60

80

100

120

140

Gl R

ate

(K

sm3

/d),

dh

pg

(psi

g)

CH

P b

arg,

gl c

hk

%, W

HP

bar

g, W

HT

de

g C

Ann P gl Chk WHT Opening P Operating P Csg P FBHP



CHK 42% to 7%

BHP increasing

CHP increasing

WHT very unstable

Oscillating CHP

Valve(s) blockage

diagnosed

Gas lift out-with design envelope


Tern Alpha (Subsea well)

• Well completed and online Mar 2015

• 5.5 x 4.5 inch tubing c/w DHPG

• The initial reservoir pressure 5600 psia

• Subsea field consisted of 2 producers & 1 injector

• Depletion strategy was to maintained natural flow

above bubble point through waterflood with gas lift as

contingency for poor waterflood performance

0

1000

2000

3000

4000

5000

6000

DH

PG

(p

sig)


Well Gas

lift on

WatInj started

& PCV

increasedWell stopped

flowing.


230 days




Reality

Assumption

• Depletion plan contingency

• GL designed for 1900 psia

• Low watercut

Actual field performance

• High watercut

• Lower pressure support

Orifice injection impossible

Unloading valves failed close

Well remain S/I

Gas lift operations barrier envelope

June 2018

SPE European Artificial Lift Conference 2018

14Slide 14

Leak from WH tie down bolt

10% of SC potential S/I

60% of SC potential at threatSAFETY

GL–production add & enhancement lever1

Tern Alpha (platform well)

• Well completed and online in May 1997

• Surveillance data (2009 & 2014) confirmed gas lift via 2nd out of 4 valves

• 2nd valve could not be consistently operated (2016) and the well died in mid 2017

• Reservoir pressure was determined - input to gas lift design

• A gas lift orifice shallowing was designed and executed (1 unloading + 1 orifice)



• 9% oil production increase via S/I well reinstatement

• 4th valve (orifice) could not be pulled

• Significant embrittlement from valves packings

• Dome pressure lost in one of the valve

Lesson – understanding of reservoir and well performance changes can identify the correct lever for adding production.




GL operating as design

Dummy valve

Dummy valve

Future opportunity to increase production potential

Deepened orifice – 17% well production increase

Spare capacity



1.5-in barrier valves selected

10%

50%

80%6,600

5,8005,400

4000

1500

5000

1,000

2,000

3,000

4,000

5,000

6,000

7,000

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

Pr

(psi

), P

I (st

b/d

/psi

)x1

00

0

WC

(%)

WC Pr (psi) PI (STB/d/psi) x 1000

A

3 SPMB

5 SPMC

4 SPM

Summary

• Operating gas lift as per design is important

• optimising /stable production and maintain well integrity

• diagnosing valve problems

• It is important to understand performance change vs.

depletion strategy assumptions for GL design / operation

• Understanding the WH barrier envelope in older wells is

important for safety and well integrity

• Regular review of reservoir and well performance KEY for

identifying gas lift production add / enhancementJune 2018 SPE European Artificial Lift Conference 2018 19

Documents

Gas lift challenges in NS TAQA’s perspectives · Gas lift challenges in NS –TAQA’s perspectives Charles Adoga, Snr Production Engineer, TAQA Europe June 2018 SPE European Artificial