1. Under Balance Drilling in Heera Field.
N&H Asset
26th May 2016

2. Introduction What is Under balance Drilling (UBD)?
It is a specialized drilling technology in which:
Intentional reduction of drilling fluid density causes the hydrostatic pressure in a wellbore to be lower than the formation pressure.
The pressure difference created, i.e. drawdown, permits the reservoir fluid to flow into the well bore and up-to the surface.
As the well is being drilled, the production can be taken up at the same time.

3. Introduction Why to do Under balance Drilling ?
Around 67% of world’s daily oil production comes from mature fields.
To improve the current production levels, field life extension is not optional but an absolute necessity.
UBD is used in Oil & Gas Industry from more than 20 years
Effective in redevelopment of matured fields, mostly for depleted/matured reservoirs to revive the production.
UBD is getting more and more popular in the world. The main reason is that its advantages can meet requirements of the current worlds petroleum exploration and production situation.
Heera field being a mature field (30 years old) appears to be a good candidate for UBD.

4. Primary Drivers for UBD Technology
Solution to Mud Loss Prevention.
Drilling without damaging formation
Immediate production benefits
Enhanced Productivity
Cost save on Mud, Logging, Well Bore Cleanup and Stimulation
Superior Reservoir management.
Filtrate Invasion
Pore
Plugging
Well-bore
Cross-Section
Filter
Cake
Crushing
Shallow
Matrix Damage
Fracture

5. Objectives of UBD:
Preventing formation damage and improving Reservoir Benefits
Improving Drilling Performance & Preventing Conventional Drilling Problems
Advantages:
Discovery of new zones
Reduces formation damage and increase intra-zone
contribution
Lower Abandonment pressure
Increases well drainage area
Provides real time reservoir evaluation/characterization
Recommended situation for UBD:
Low pressure/severely depleted reservoirs
Highly fractured reservoirs
Reservoirs with a narrow margin between fracture pressure and pore pressure

6. UBD Project in ONGC HK Wells
ONGC being a major national oil company has taken many steps for implementing new drilling technologies for reducing losses from its matured fields.
Initially Based on Cost Benefit Analysis 3 Wells of Heera Field and 3 wells of MH Asset were identified.
Identified 3 Wells of HK platform, #2H, #6H, #9H
Rig Identified
Victory Driller

7. Heera Field
Heera and South Heera fields are separated by a sealing fault
Heera
Discovered in 1977
Put on production in Nov.1984
Injection started in Sept. 1990
South Heera
Discovered in 1990
Put on production in Nov.1995
Injection started in Oct. 1997
North Heera
South
Heera
Mid Heera

8. Heera Field Stratigraphy
Oil bearing formations
Panna, Bassein, Mukta & Heera
Free gas : Bandra
Bassein Pay (65% of total IOIP)
Bassein pay subdivided into B1,B2,B3 and B4 layers.
Majority of wells completed in Bassein pay.
Current Oil production contribution
Bassein - 43%
Mukta + Bassein - 31 %.
Mukta - 12%
Panna - 11%

9. UBD in Heera Field HK
HK-6H
HK-2H
HK-9H
Low Pressure
High Pressure
Pay zone of wells HK#2H and HK#9H have been drilled successfully with UBD. In well HK#6H UBD is in progress.
First time in ONGC this technology is being implemented
Drilling till Bassein top has been done conventionally,
After application of UBD technology 30% increase in productivity is expected
Static Reservoir pressure near UBD location ranges from psi

10. Project Engineering
Oil+ N2

11. Details of Well Data of HK Wells
Formation
HK # 2H
TVDSS/MDKB (m)
HK # 6H
HK # 9H
Bandra
769/881
785/927
772/952
Alibagh
1380/1841
1378/1899
1390/2087
Heera
1469/2005
1471/2072
1482/2300
Mukta
1516/2203
1517/2162
1532/2495
Bassein
1539/2350
1537.5/2277
1553/2656
Drilled with UBD technology
365
910
2047
2342
392
929
2066
2247
400
989
2311
2617
Mud Wt Window
1909
1910
2175

12. Schematic well diagram of HK#2H Objective: OP in Bassein pay
HD: 1390m at B top and Azimuth: 220°N
30" piled up to 160m
20“ Shoe at 365m
6” DH from 2342 to 2534m in Bassein pay (192m)
7”shoe at 2342m (~B top)
Plan Days: 74
Spud date:
Hermetical test date:
Phase
Plan Days
Actual Days
26” hole 4 3
17 ½” 8 5
12 ¼” 11 12
8 ½”
UBD Preparation 17 16
6” DH
4.50
Lower Completion
5.50
( )
Upper Completion
Dismantling of UBD 7
Total Days 73
13 3/8” Shoe at 910m
9 5/8” Shoe at 2047m
(Heera Top)

13. 6” DH from 2342 to 2534m in Bassein pay (192m)
LWD log motif of well HK#2H
6” DH from 2342 to 2534m in Bassein pay (192m)

14. Schematic well diagram of HK#9H Objective: OP in Bassein pay
HD: 1740m at B top and Azimuth: 225°N
30" piled up to 160m
20“ Shoe at 400m
6” DH from 2619 to 2855m in Bassein pay (236m)
7”shoe at 2619m (Mukta bottom)
Plan Days: 59
Spud date:
Hermetical test date:
Phase
Plan Days
Actual Days
26” hole 4
4.50
17 ½” 8 5
12 ¼” 12 11
8 ½” 9
UBD Preparation 6
6” DH
Lr. Completion
4 ( )
Up. Completion 7
Total days 58
13 3/8” Shoe at 989m
9 5/8” Shoe at 2311m
(Heera Top)
Losses encountered in 12 ¼” section in Bandra pay. Cumulative Mud loss: 1300 barrels.
Total Pills placed: 01 LCM pill.
H/U while lowering P/O liner and C/o Stabilizer trip.

15. 6” DH from 2619 to 2855m in Bassein pay (236m)
LWD log motif of well HK#9H
6” DH from 2619 to 2855m in Bassein pay (236m)

16. Schematic well diagram of HK#6H Objective: OP in Bassein pay
HD: 1450m at B top and Azimuth: 258°N
30" piled up to 172m
20“ Shoe at 392m
Losses encountered in 12 ¼” section in Bandra pay. Cumulative Mud loss: 7664 barrels.
Total Pills placed: 09 LCM and Four Stop loss pill.
6” DH from 2249 to 2420m In Bassein pay (171m)
7” Shoe at 2249m (~B top)
Plan Days: 65
Spud date:
Hermetical test date:
Phase
Plan Days
Actual Days
26” hole 4 8
17 ½” 6
12 ¼” 11 25
8 ½”
UBD Preparation
7.50
6” DH 5 10
Completion
13.50
Total days 57
13 3/8” Shoe at 929m
9 5/8” Shoe at 2066m
(Heera Top)

17. 6” DH from 2249m to 2420m in Bassein pay (171m)
LWD log motif of well HK#6H
6” DH from 2249m to 2420m in Bassein pay (171m)

18. Flow test and ECD parameters Total oil pumped in WF line
Well no.
6” DH length
(m)
Avg. ECD maintained
(ppg)
Avg. flow test
(bopd)
Total oil pumped in WF line
HK#2H
192
4.55 – 4.43
4.0 – 4.15
652*
1450
HK#9H
236
4.3 – 3.8
1685*
3200
HK#6H
171
4.0 – 4.5
1800
** 200 psi drawdown has been given during UBD drilling.

19. Flow Paths Platform N2 Slurry Solids Gas Water Oil Oil/Water
ANNULUS RETURNS
Oil/Water
Solids
Produced Oil/Water
Water
Slurry
Oil
Gas
Inj. Pump
Platform

20. Actual set up at site

21. Rotating Control Device (RCD)
UBD Choke System
Rotating Control Device (RCD)

22. Injection and Bleed-off Manifold

23. Tank Farm and Separation System

24. N2 Generation Unit

25. Lesson Learnt & Highlights of UBD Operations in HK Wells
Lessons learnt:
Efforts to be taken for minimizing the NPT in future wells.
Operation of LWD tools in UBD condition is a challenge.
Frequent RCD failure observed in UBD drilling is a concern.
UBD is cost intensive and increasing rig days against planned days to be minimised.
Highlights:
Provide real time Reservoir Potential evaluation while drilling in HK wells.
5000 barrel oil transported to Heera pipeline after drilling three UBD wells
Production from damage free hole sustain for a longer period especially in longer drain hole.

26. Thank You

27. Bottom Hole Circulating Pressure
ECD in ppg
Drilled with Crude
Av ECD 4.1
Drilled with Base Oil
Av ECD of 4.6
Flowing the well lowers the ECD / increases drillability
Measured Depth

28. Inflow Test Result (needs to be updated for the wells drilled)
Av. FWHP Psi
Av. Prod. Gas scfm
Ave. Prod. Oil BOPD
Flow Test 1
N2 Rate 1
285
450
478
N2 Rate 2
195
2,721
290
N2 Rate 3
141
2,594
330
Av Result 1
207
1,922
366
Flow Test 2
112
777
635.44
110
838
669.00
Av Result 2
111
808
652
Test 1 Av. GOR of 7564 scfm / bbls of oil
Test 2 Av GOR of 1783 scfm/ bbls of oil

29. Frictional Plays important role in deciding the DH length
Well Engineering
BHP = Phydro +Pfric + Psurface
Frictional Plays important role in deciding the DH length

30. Primary Drivers for UBD Technology
To improve the effective penetration rate NPT has to be reduced.
ONGC being a major national oil company has taken many steps of reducing losses from its matured field in drain hole.
System LCM & NDDF for minimizing reservoir damage.
LCM form various vendors.
Using of low specific gravity material.
Hollow gas sphere
Micro bubble technology.
Mud Loss Impact over Total NPT
% , & %

31. Well Profile of HK#2H

32. Well Profile of HK#9H Activity Plan Days Rig Up and Test 8 UB Drilling
20" Casing 400m
Ang 16
Activity
Plan Days
Rig Up and Test 8
UB Drilling 5
Lower Completion
Upper Completion 7
13 3/8" Casing 989m
Ang 57
TVD
9 5/8" Casing 2311m
Ang 69
7" Casing 2617m
Ang 86
N2 Inj 2145m
Ang 60
TD 2951m
Ang 90
TVS

33. UBD Drilling Days for Each Platform ( For Three Wells)
S.NO
Details
As per Proposal
Planned 1
Transportation of UBD Equip. 3 2
Rig Up for 3 Wells 7 24
UBD Drilling + Lower Completion 66 37
Upper Completion 22 4
Rig Down and Transportation 5
Exigency 8
Total Days 91 94

34. Platform HK Plan vs Actual
Activity
HK # 2H
HK # 9H
HK # 6H
Plan
Actual
Drilling Days 32 29 34
57.5
UBD Days
Rig up days 17 19 8 5*
7.5
UBD Drilling Days
4.5
11.5 5
Lower Completion
5.5
Upper Completion 7
Rig down Days
Total UBD 42
35.5 25 26
Total of Days on Well 74
64.5 59 37
#6H – Losses in 12¼” Section
*#9H – UB Drilling expected to start by 29th Apr. 2016

35. Highlights and way forward in UBD
Provide real time Reservoir Potential evaluation while drilling in HK wells.
5000 barrel oil transported to Heera pipeline after drilling three UBD wells
Production from damage free hole sustain for a longer period especially in longer drain hole.