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
2011 SPE/IADC Middle East Drilling Technology Conference, Muscat, 24-26 October 2

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


42 deep HPHT gas fields developed using potassium
and cesium formate brines, 1995-2011
Country Fields Reservoir Description
Matrix Depth, TVD Permeability Temperature
type (metres) (mD) (oC)
Germany (7) Walsrode,Sohlingen Sandstone 4,450-6,500 0.1-150 150-165
Voelkersen,I dsingen,
Kalle, Weissenmoor,
Simonswolde

Hungary (2) Mako , Vetyem Sandstone 5,692 - 235
Kazakhstan (1) Kashagan Carbonate 4,595-5,088 - 100
Norway (10) Huldra ,Njord Sandstone 4,090-7,380 50-1,000 121-200
Kristin,Kvitebjoern
Tune, Valemon
Victoria, Morvin,
Vega, Asgard

Pakistan (2) Miano, Sawan Sandstone 3,400 10-5,000 175
Saudi Arabia (7) Andar,Shedgum Sandstone 3,963-4,572 0.1-40 132-154
Uthmaniyah
and
Hawiyah,Haradh
Tinat, Midrikah carbonate

UK (12) Braemar,Devenick Sandstone 4,500-7,353 0.01-1,000 123-207
Dunbar,Elgin
Franklin,Glenelg
Judy, Jura, Kessog
Rhum, Shearwater
West Franklin

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


Conventional formate drilling fluid formulation -
in field use since 1993 and good to 320oF

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

Component Function Concentration

Density
Lubricity
Formate brine 1 bbl
Polymer protection
Biocide

Viscosity
Xanthan 0.75 - 1 ppb
Fluid loss control

Ultralow vis PAC and modified
Fluid loss control 3 or 4 ppb of each
starch

Sized calcium carbonate Filter cake agent 20 ppb

Buffer
K2CO3/KHCO3 0 – 6 ppb
Acid gas corrosion control

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

6

Formate-based drilling fluids

7

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

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


Cesium formate brine first used as a combined
drill-in and completion fluid in the Huldra field,
2001

• 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


Huldra – drill-in, logging and completion times
(days) with cesium formate brine in well

A-4 A-5 A-6 A-8 A-9 A-11 Average
(189 m ) (263 m) (344 m) (257 m) (230 m) (336 m) (231 m)

Drill-in 5 8 20 15 7 11 11

Logging 0 3 1 7 3 2 2.7

Lower
11 6 5 6 5 5 6.3
completion

Upper
4 5 4 4 9 4 5
completion

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 A-5 A-6 A-8 A-9 A-11 Average
(189 m ) (263 m) (344 m) (257 m) (230 m) (336 m) (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
5.6 28.3 12.8 24.3 11 15.7 16.3
displacements

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)

Plateau production from first 3 wells
120.00

Gas

Recovery of Reserves (% of original estimate)
Condensate
- 10 MM m3 gas /day 100.00

- 30,000 bbl/day condensate 80.00

60.00

80% of hydrocarbon reserves produced 40.00

by Year 6
20.00

0.00
0 2 4 6 8 10
Time since start-up (years)


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

100
90
Recovery of Gas Reserves (%)

80
70
60
50
Huldra
40
Tune
30
20
10
0
0 5 10 15

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
120
years

Recovery of Condensate Reserves (%)
100

80

60
Huldra
Tune
40

20

0
0 5 10

Source : Norwegian Petroleum Directorate- Fact Pages - November 2009


Seven years of cesium formate brine use as
combined drill-in and completion fluid in Kvitebjoern
field, 2004 -present

• 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


A few of the highlights from Kvitebjoern

Completion
Kvitebjoern time
well (days) Operator comments after well testing (Q3 2004 )

A-4 17.5 “The target well PI was 51,000 Sm3/day/bar This target
would have had a skin of 7”
A-5 17.8
“A skin of 0 would have given a PI of 100,000”
A-15 14.8
“THE WELL A-04 GAVE A PI OF 90,000 Sm3/day/bar
A-10 15.9 (ANOTHER FANTASTIC PI)”
A-6 12.7 *
The Well PI was almost double the target
Fastest HPHT well completion
in the North Sea


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)

2011 SPE/IADC Middle East Drilling Technology Conference, Muscat, 24-26 October
22


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
Flow check fingerprint
• No differential sticking for a Huldra well

• No well bore instability*
Duration of
flow back
Fluid Gain
(bbl)
(minutes)

• Pipe and casing running speeds are fast
30 0.8

• Mud conditioning and flow-check times are short
15 0.56

• Displacements simplified, sometimes eliminated
20 0.44

Formate drilling fluid = formate completion fluid
30 0.56

* 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”



Good reservoir definition

• 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

• 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

29

SPE 145562

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