4_offshore gas well deliquification in southern north sea

1Shell Exploration & Production

File Title: PTPC200

7 Gas

Well D

eliquification

Strategy

in EPE

Cop

yright: Sh

ell E

xploratio

n & Produ

ction Ltd.

Offshore GWD in Southern North Sea

3rd European Conference on Gas Well Deliquification - 16 September 2008

Kees Veeken*, Charles Mombo, Majeed Yousif, Peter de Boer, Bert Lugtmeier, Al Zanimonsky, Ewout Biezen

Danial Leybourne*, Gert de Vries and Matthias Verstraeten

(NAM-EPE, Assen)

Shell Exploration & Production

2

Contents

Southern North Sea gas asset

Benefit of deliquification

Offshore deliquification

Comparing options

Retrofitting foam

Mobile compression

Production chemistry aspects of applying foam offshore


3ONEgas West (UK) ONEgas East (NL)

UK & NL, 60 platforms, 300 gas wells, vintage 1968-2008

2008 production 35 106 sm3/d (1250 MMscf/d)

30% liquid loading 3.5 106 sm3/d at stake (10%)


4

Benefit of Deliquification

Determine incremental reserves based on reduction of minimum stable rate (Qmin) in Decline Curve Analysis (DCA)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00Cumulative Gas Production (e9 m3)

Ga

s Pr

odu

ctio

n R

ate

(e6

m

3 /d)

Qmin=0.1 mln m3/dUR=1.58 Bcm

Qmin=0.05 mln m3/dUR=1.65 Bcm

(RF +4%)

Incremental recovery1%-10%

20-200 106 m3 per well


5

Benefit of Deliquification

Determine incremental reserves based on reduction of abandonment pressure (Pab) in Material Balance (MB)

0

50

100

150

200

250

300

350

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Gas Produced (mrd m3)

P/Z

(ba

ra @

da

tum

le

ve

l)

K7-FB-101

K7-11

Material Balance

Qmin=0.15 mln m3/d(P/Z)ab=28 barUR=1.66 Bcm

(RF +2%)

Qmin=0.3 mln m3/d(P/Z)ab=34 barUR=1.62 Bcm

All wells potential candidates

5-25 109 m3


6

Determine Abandonment Point [Qmin,Pab]

Quick & dirty: ignore holdup use Turner Qmin & AFBC Pab

Pab = [B*FTHP2+A*Qmin+(C+F)*Qmin2]0.5 where

FBHP2 = B*FTHP2+C*Qmin2 and Pres2-FBHP2 = A*Q+F*Q2

Prosper modelling: include holdup use Modified Gray

Deliquification

Compression: reduce FTHP

Stimulation: reduce A (and F)

Velocity string: reduce ID

Foam: WGR=0

Downhole pump: WGR=CGR=0

BHP

Qgas

Wet gasWGR=0WGR=CGR=0

Holdup


7

Deliquification Scenarios

0

20

40

60

80

100

120

140

160

180

200

20 30 40 50 60

Reservoir Pressure (bara)

Gas

R

ate

(e3m

3/d)

BC FTHP=10 A=0.01ID=0.0635 WGR=0 WGR=CGR=0

Base Case:ID=0.109 m (5" tubing)A=20 bar2/e3m3/dTHP=20 barWGR=89e-6 m3/m3 CGR=10e-6 m3/m3

41333027Velocity string

Pab (bara)Qmin (103 m3/d)Scenario

0

56

82

55

78

Prosper

25240Downholepump

423738Foam

433879Stimulation

383656Compression

514779Base Case

ProsperAFBCTurner

Abandonment Point[Qmin,Pab]


8

Minimum & Optimum ID

Minimum ID = ID for minimum PabMinimum ID decreases with A

Minimum ID results in initial capacity ~10% of inflow constraint

Optimum ID depends on connected volume, typically 1x-4x Minimum ID

KH (mD.m)100,000 10,000 100 10

1000

Inflow constrained

Outflow constrained


9

Offshore Deliquification - Boundary Conditions

Installation = Costly [cost offshore = 5x cost onshore]

Workover typically not justified

Need retrofit solution(s)

Subsurface safety valve required

Completion types of varying vintage, generally not monobore

Enable future application of new technology

Operation = Infrequent & Costly [no crane, no helideck]

Assume 1 maintenance visit per 2+ yrs using work platform

Need low maintenance / high reliability solutions

Automation (SCADA) is key


10

Offshore Ranking

4315Mobile compression

2224Plunger

2214Downhole pump

3205Wellhead compression

3204Gas lift

5531Insulated tubing

4342Automated batch foam

4442Automated intermittent

5453Water shut-off

5532Velocity string

3

4

Benefit

333Continuous foam

5

Uptime

Stimulation

Technique

4

Opex

5

Capex

5 Highest Score0 Lowest ScoreSlam Dunk

Probable Win

Possible Win


11

Offshore Reliability is Key

Critically compare batch Vs continuous

Field trials

Retrofit capillary foam injection

Use SSSV control line

Utilise LMGV cavity

Integral deployment using Torus

SSSV

SVFWV

LMGVUMGV=SSV

KWCon

trol

line

flu

id a

ndSu

rfactant

Actuated Manual

SSSV

SVFWV

LMGVUMGV=SSV

KW

Surfactant

Controlline fluid

SSSV

SV=SSVFWV=SSV

LMGVUMGV

KW

Con

trol

line

flu

id

Surfactant


12

Utility Tree Prepares Gas Well for Rainy Day

Reduce future cost of continuous foam, velocity string,

gas lift, plunger, contingency control line etc.

PressureFoam

ElectricalGas Injection

HydraulicPressure

FoamElectrical

Gas Injection

Hydraulic

Asleep ContinuousFoam


13

X-FA Batch Foam Trial

X-FA-101 "

Dead well

65 m3 slug of water produced after batch (2x)

Too much water to handle, wait for continuous foam trial

X-FA-106 !!!!

Dead well

Batch job: 25 L surfactant + 200 L 3% KCl, 1x per 1-2 days

Gain: 60 103 m3/d (2 MMscf/d), uptime 50%, defoamer at startup

X-FA-107 "

Stable well

Foam impaired near-wellbore (2x), cleaned up


14

K14FA1P.FPTR-815F.U

Mm3/dK14FA1P.TT-60.U

bargK14FA1P.TT-10.U

bargK14FA1P.PT-62.U

barg

K14-FA-106

10/08/2008 07:33:22.548 04/09/2008 07:33:22.54825.00 days

0.13

0.18

0.23

0.28

8.E-02

0.33

-20

80

-20

80

-50

50

13.4

19.4

27.6

0.128

106 THP

106 THT

Ambient THT

106 Qg

Qmin~70 103 m3/d


15

Mobile Compression Offshore

Cost of wellhead compression generally prohibitive

Power supply, space and weight restrictions, logistics and interfacing

Install compression package on mobile jackup

Allows cost sharing and production of all platform wells instead of single well

MOAB at Trent


16

Summary

Large scope exists for offshore deliquification (5-25 109 m3)

Determine deliquification benefit via decline curve analysis and/or material balance using abandonment point [Qmin,Pab]

Best determine abandonment point via outflow model (e.g. Prosper)

Turner Qmin and AFBC Pab provide reasonable approximation, however ignore holdup and mislead velocity string selection

Offshore deliquification challenges are related to high cost and low frequency of offshore installation and intervention

Improve reliability of continuous foam by optimising hardware, fluid access and deployment [environmental aspects covered in 2nd part]

Tailor plunger lift based on onshore experience

Evaluate offshore application of mobile compression


File Title: PTPC200

7 Gas

Well D

eliquification

Strategy

in EPE

Cop

yright: Sh

ell E

xploratio

n & Produ

ction Ltd.

Production Chemistry Challenges Applying Foam Offshore

3rd European Conference on Gas Well Deliquification - 16 September 2008

Danial Leybourne, Gert De Vries and Matthias Verstraeten


18

Product specifications

Stability (winterized, non-viscous)

Non-corrosive

Compatible (i.e. solids, emulsion)

Does it foam?

Is there an anti-foamer?

Minimal impact on quality Water Overboard (WOB)

Minimal impact on quality condensate

Registration/Permits

CEFAS/MSDS

Location specific

Challenges Applying Foam Offshore

10


19

Compatibility

Compatible with produced fluids no solid / emulsion generation

Compatible with system chemical compatibility


20

Foam Performance

Poor>120Moderate80 < x < 120

Good < 80 ResultFoam build up time (s)

Poor>120Moderate80 < x < 120

Good < 80 ResultFoam build up time (s)

PoorModerate PoorProduct E

Moderate PoorModerate PoorProduct D

GoodModerate PoorProduct C

GoodGoodProduct B

GoodGoodProduct A

> 100.000 mg/L Cl-< 5.000 mg/L Cl-Salinity

High salinityLow salinity

PoorModerate PoorProduct E

Moderate PoorModerate PoorProduct D

GoodModerate PoorProduct C

GoodGoodProduct B

GoodGoodProduct A

> 100.000 mg/L Cl-< 5.000 mg/L Cl-Salinity

High salinityLow salinity

11


21

Performance with Condensate

Product A increasing condensate vol%

Performance vs condensate %

0

50

100

150

200

250

5 40 60 90 95 100Condensate %

Tim

e (s)

Build up time of foam

Half-life time of foam


22

Anti-Foam Performance

Anti-foam collapses foam & stops re-foaming

PoorPoorPoorPoorProduct E

PoorPoorPoorModerateProduct D

PoorPoorPoorPoorModerateProduct C

PoorPoorPoorPoorGoodProduct B

ModerateGoodPoorPoorModerateProduct A

Product 5Product 4Product 3Product 2Product 1Anti-foamer Foamer

PoorPoorPoorPoorProduct E

PoorPoorPoorModerateProduct D

PoorPoorPoorPoorModerateProduct C

PoorPoorPoorPoorGoodProduct B

ModerateGoodPoorPoorModerateProduct A

Product 5Product 4Product 3Product 2Product 1Anti-foamer Foamer

Poor>50

Moderate>30 < x < 50

Good

12


23

Oil in Water

Foam / anti-foam does have an impact on oil in water

Package to mitigate against Increase in oil in water De-oilers clarifiers

Foam / anti-foam includingdemulsifier blended in

Daily legal limit = 30 mg/L

Max. daily discharge = 100 mg/L (~0.01 vol%)

01000020000300004000050000600007000080000

Hyd

roc

arbo

n

con

ten

t (pp

m)

1 2 3 4

Batch

Hydrocarbon content X-FA


24

Specifications for foam & anti-foam products are key in avoiding operational problems and ensuring success

Performance tests

Lab tests are representative in screening products for field trials

Test foam products on produced fluids from candidate well to ensure maximum success in field trials (salinity, hydrocarbon tolerance)

Foam / anti-foam compatibility

Foam has shown to affect the oil in water content

Steer to the chemical service industry from Shell

More products which meet requirements

Products (or package of products) which do not damage the water quality and meet the legal requirements for offshore

Summary

13


25

Foam team

Gert De Vries

Jeltje Schouwstra

Jeroen Fijn

Ewout Biezen

Majeed Yousif

Peter De Boer

Erik van der Vegt

Matthias Verstraeten

Well services

Operations

Many thanks to:

4_offshore gas well deliquification in southern north sea

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