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

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.

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.

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

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

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

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

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%

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 1200-1250 psi

Project Engineering Oil+ N2

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 8.6-9.2 9.2-10.2 8.6-9.0 1909 1910 2175

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: 10.12.15 Hermetical test date: 17.03.16 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 (22.04.16) Upper Completion Dismantling of UBD 7 Total Days 73 13 3/8” Shoe at 910m 9 5/8” Shoe at 2047m (Heera Top)

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)

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: 05.12.15 Hermetical test date:13.03.16 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 (10.05.16) 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 7”liner @2536m, P/O liner and C/o Stabilizer trip.

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)

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: 01.12.15 Hermetical test date:10.03.16 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)

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)

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.

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

Actual set up at site

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

Injection and Bleed-off Manifold

Tank Farm and Separation System

N2 Generation Unit

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.

Thank You

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

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

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

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 2013-14 - 10% , & 2014-15 -8%

Well Profile of HK#2H

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

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

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

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.