spe 145562

SPE 145562

Life Without Barite: Ten Years of

Drilling Deep HPHT Gas Wells With

Cesium Formate Brine

John Downs

Cabot Specialty Fluids

2011 SPE/IADC Middle East Drilling Technology Conference, Muscat, 24-26 October

Cesium formate brine : Drill-in, completion,

workover and suspension fluid for HPHT gas wells

• Density up to 19.2 ppg/SG 2.3

• Drill-in and completion fluid

• Non-toxic, non-hazardous – safe to handle

• Little or no risk to the environment

• Compatible with all reservoirs

• Extends the thermal stability of polymers

• Less corrosive than bromide brines

• Stabilises shales

• Inhibits hydrates


Cesium formate brine produced by Cabot in

Canada from pollucite ore

Pollucite ore

Cs0.7Na0.2Rb0.04Al0.9Si2.1O6·(H20)

• Mined at Bernic Lake, Manitoba

• Processed on site to Cs formate brine

• Cs formate brine production 8,000 bbl p.a. of 19.2 ppg

• Brine stocks > 30,000 bbl @ 19.2 ppg

• Brine supplied on leasing terms (i.e. per bbl per day)

• Currently manage 30-40 jobs per year


Leasing cesium formate brine

Green and sustainable model – recognised by United Nations


Conservation ( i.e. minimisation of cesium formate brine losses during

transport, use and reclamation) is a key and essential feature of Cabot’s

Chemical Leasing business model

4

42 deep HPHT gas fields developed using potassium

and cesium formate brines, 1995-2011

Country Fields Reservoir Description

Matrix

type

Depth, TVD

(metres)

Permeability

(mD)

Temperature

(oC)

Germany (7) Walsrode,Sohlingen

Voelkersen,I dsingen,

Kalle, Weissenmoor,

Simonswolde

Sandstone 4,450-6,500 0.1-150 150-165

Hungary (2) Mako , Vetyem Sandstone 5,692 - 235

Kazakhstan (1) Kashagan Carbonate 4,595-5,088 - 100

Norway (10) Huldra ,Njord

Kristin,Kvitebjoern

Tune, Valemon

Victoria, Morvin,

Vega, Asgard

Sandstone 4,090-7,380 50-1,000 121-200

Pakistan (2) Miano, Sawan Sandstone 3,400 10-5,000 175

Saudi Arabia (7) Andar,Shedgum

Uthmaniyah

Hawiyah,Haradh

Tinat, Midrikah

Sandstone

and

carbonate

3,963-4,572 0.1-40 132-154

UK (12) Braemar,Devenick

Dunbar,Elgin

Franklin,Glenelg

Judy, Jura, Kessog

Rhum, Shearwater

West Franklin

Sandstone 4,500-7,353 0.01-1,000 123-207

USA (1) High Island Sandstone 4,833 - 177


6

Conventional formate drilling fluid formulation -

in field use since 1993 and good to 320oF

Component Function Concentration

Formate brine

Density

Lubricity

Polymer protection

Biocide

1 bbl

XanthanViscosity

Fluid loss control0.75 - 1 ppb

Ultralow vis PAC and modified

starchFluid loss control 3 or 4 ppb of each

Sized calcium carbonate Filter cake agent 20 ppb

K2CO3/KHCO3

Buffer

Acid gas corrosion control0 – 6 ppb

Simple, effective, non-damaging reservoir drill-in fluid

Used to drill entire wells, top to bottom, in sensitive environments (e.g. Barents Sea)

7

Formate-based drilling fluids

Cesium formate brine

Where does it provide the highest value ?

As a combined drill-in and completion fluid - enabling operators to construct high-angle open hole screen completions in HPHT tight gas reservoirs

• Combined drilling and completion fluid (“one filtrate”)

• Non-damaging to reservoir and screens

• Cleans-up naturally during start-up (10-20 hours)

• Low skins

• No well stimulation required

Perhaps the only fluid that can do this in an HPHT environment

8

Advantages of open hole screen completions in

high-angle HPHT wells*

Improved economics and lower risk

• Maximise reservoir contact and production- Larger inflow areas in contact with reserves

- Allow higher flow rates with lower flow resistance

- Good results (low skins) with stand-alone screens

• Lower cost- Quicker and easier to install, less NPT

- 10% lower tangibles cost

• More robust than cased holes- Less affected by formation compaction over time

• Lower HSE risk than cased holes - No explosives , no live well work, fewer lifts, etc

* From “HPHT Wells Best Practices Course” by Think Well Ltd


Cesium formate brine used by BP and Statoil as

combined HPHT drill-in and completion fluid in N. Sea

28 high-angle development* wells drilled and completed in 6 HPHT offshore gas fields

• Huldra (6 )

• Devenick (1)

• Kvitebjoern (8 O/B and 5 MPD)

• Valemon (1)

• Kristin (2)

• Vega (5)

* Except Devenick and Valemon (appraisal wells)

Mostly open hole stand-alone sand screen completions

Also Tune field : drilled with 13.3 ppg K formate brine , completed in K/Cs formate brine and

suspended in K/Cs formate brine for 6-12 months


Tune field – semi-HP/HT gas reservoir in the North

Sea drilled and completed with formate brines

11

4 wells : 1,100-2,950 ft (350-900 m) horizontal reservoir sections. Suspended for 6-12

months in K/Cs formate brine after completion


HPHT gas fields in northern North Sea drilled

and completed with cesium formate brine

Almost every field development (oil and gas) on this map has used formate brines as well

construction fluids . Zinc bromide brine no longer used in Europe – too hazardous and damaging


HPHT gas fields in the Norwegian Sea drilled

and completed with cesium formate brine

Formate brines also used as well construction fluids in Asgard, Draugen, Morvin and Njord fields


• Offshore Norway

• Gas condensate field

• 6 wells

• BHST: 297oF (147oC)

• TVD : 12,795 ft (3,900 m)

• Fluid density: 15.76- 16.34 ppg (SG1.89-1.96)

• 754-1,125 ft (230-343 m) x 81/2” reservoir sections

• Hole angle : 45-55o

• 1–2 Darcy sandstone

• Open hole completions, 6 5/8” wire wrapped screens

Cesium formate brine first used as a combined

drill-in and completion fluid in the Huldra field,

2001


Huldra – drill-in, logging and completion times

(days) with cesium formate brine in well

A-4

(189 m )

A-5

(263 m)

A-6

(344 m)

A-8

(257 m)

A-9

(230 m)

A-11

(336 m)

Average

(231 m)

Drill-in 5 8 20 15 7 11 11

Logging 0 3 1 7 3 2 2.7

Lower

completion 11 6 5 6 5 5 6.3

Upper

completion 4 5 4 4 9 4 5

Total 20 22 30 32 24 22 25


Drill, log and run lower completion in drilling fluid. Then displace to clean cesium

formate brine and run upper completion. Finally displace to packer fluid

Huldra – Fluid losses while drilling (cubic metres)

A-4

(189 m )

A-5

(263 m)

A-6

(344 m)

A-8

(257 m)

A-9

(230 m)

A-11

(336 m)

Average

(231 m)

With cuttings 2.6 16.4 48 9.6 23.8 17.7 19.7

Other surface 1.5 3.3 10.1 2.2 12 17.1 7.7

Downhole 7.6 10.8 46.4 0 0 0 10.8

Well

displacements 5.6 28.3 12.8 24.3 11 15.7 16.3

Tripping 6.5 7.2 6.3 3.6 1.6 2.8 4.7

TOTAL 23.8 66 123.6 39.7 48.4 53.3 59.1


Huldra – Production of recoverable gas and

condensate reserves since 2001 (NPD data)

17

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0 2 4 6 8 10

Reco

very

of

Reserv

es (

% o

f o

rig

inal

esti

mate

)

Time since start-up (years)

Gas

Condensate

Plateau production from first 3 wells

- 10 MM m3 gas /day

- 30,000 bbl/day condensate

80% of hydrocarbon reserves produced

by Year 6


Gas production from Tune and Huldra fields drilled

and completed with K/Cs formate brine

90% recovery of gas reserves (16-18 billion m3) produced in 7 to 8 years

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15

Rec

ove

ry o

f G

as

Res

erv

es

(%

)


Huldra

Tune

Source : Norwegian Petroleum Directorate- Fact Pages - November 2009


Condensate production from Tune and Huldra fields

drilled and completed with K/Cs formate brine

90% recovery of condensate reserves (3-5 million m3) produced in 5 to 7

years

Source : Norwegian Petroleum Directorate- Fact Pages - November 2009


0

20

40

60

80

100

120

0 5 10

Rec

ove

ry o

f C

on

de

nsa

te R

es

erv

es

(%

)


Huldra

Tune

• Offshore Norway, 190 m water depth

• Gas condensate field, 775 bar

• 13 wells to date – 8 O/B, 5 in MPD

• BHST: 311oF (155oC)

• TVD : 13,120 ft (4,000 m)

• Fluid density: 16.8 ppg (SG 2.02) for O/B

• 914 -1,910 ft (279-583 m) x 81/2” reservoir sections

• Hole angle : 20-40o

• 100 mD sandstone, long interbedded shale and coal sequences

• 6 wells completed in open hole : 300-micron single wire-wrapped

screens. Remainder cased

Seven years of cesium formate brine use as

combined drill-in and completion fluid in Kvitebjoern

field, 2004 -present


A few of the highlights from Kvitebjoern

Kvitebjoern

well

Completion

time

(days)

A-4 17.5

A-5 17.8

A-15 14.8

A-10 15.9

A-6 12.7 *

Fastest HPHT well completion

in the North Sea

21

“The target well PI was 51,000 Sm3/day/bar This target

would have had a skin of 7”

“A skin of 0 would have given a PI of 100,000”

“THE WELL A-04 GAVE A PI OF 90,000 Sm3/day/bar

(ANOTHER FANTASTIC PI)”

Operator comments after well testing (Q3 2004 )

The Well PI was almost double the target


Economic benefits from the use of cesium

formate brine in HPHT gas field developments

Improved HPHT well control and safety

• No well control incidents in 28 HPHT drilling and completion ops

over 10 years (maybe 800 days in HPHT high-angle open hole ?)

• Factors contributing to improved well security and safety:

- Elimination of barite and its sagging problems

- Elimination of oil and its gas solubility problem

- Low solids brine Low ECD* and swab pressures

- Inhibition of hydrates

- Ready/rapid surface detection of well influx

- No hazardous zinc bromide !

* ECD in Huldra, Kvitebjoern and Kristin wells : 0.33-0.50 ppg (SG 0.04-0.06)




Improved well performance and recovery of reserves

• “High production rates with low skin” *

• “ We selected cesium formate to minimise well control problems

and maximise well productivity”*

* Quotes by Statoil relating to Kvitebjoern wells (SPE 105733)


Economic benefits from use of cesium


Faster completions

- Drill-in and completing with cesium

formate allows open hole completion

with screens

- Clean well bores mean no tool/seal

failures or blocked screens

- Completion time 50% lower than wells

drilled with OBM

Time saved per well: 25 days

Quote by operator:“ fastest HPHT completion operation ever performed in North Sea (12.7 days)”


Economic benefits from use of cesium

formate brine in deep gas field developments

Operational efficiencies Lower NPT Lower costs

• No differential sticking

• No well bore instability*

• Pipe and casing running speeds are fast

• Mud conditioning and flow-check times are short

• Displacements simplified, sometimes eliminated

Formate drilling fluid = formate completion fluid

* Quote by operator : “ No washouts were experienced in any of the wells during drilling through long sections of

interbedded shales in the Kvitebjoern reservoir (50/50 shale and sand ) with cesium/potassium formate fluid”

Duration of

flow back

(minutes)

Fluid Gain

(bbl)

30 0.8

15 0.56

20 0.44

30 0.56


Flow check fingerprint

for a Huldra well



Good reservoir definition

26

• High density filtrate and no barite

• Filtrate Pe up to 259 barns/electron

• Unique Cs feature - makes filtrate invasion

highly visible against formation Pe of 2-3 b/e

• Ideal for defining permeable sands

• Consistent and reliable net reservoir definition

from LWD

“Using photoelectric factor and bulk density data, combined with resistivity measurements from both

the LWD drill pass and the ream pass, produces a very reliable and consistent net reservoir

definition.” (SPE 105733)




Good reservoir definition

27

• Highly conductive fluid

• Clear resistivity images

• Information provided:

- structural dip

- depositional environment

- geological correlations


Summary

10 years of field use has demonstrated that cesium formate brine

can improve the economics of HPHT gas field developments by:

• Enabling long high-angle well constructions completed in

open hole with screens

• Making the well construction process faster and easier

• Improving well/operational safety and reducing risk

• Delivering unimpaired wells with high production rates

• Enhancing reservoir definition


www.formatebrines.com

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