Dual Casing Running for deep water spud in

OPTIONS Presentation Focusing the issue Deep water operation: Riserless top hole section Deep Water Dual Casing: MAIN PHASES OPTIONS REQUIRMENTS Applications Conclusions 2

Deep water activities: extreme environment heavy load conditions with unconsolidated sea bed high daily spread rate The improvement of operations with the aim to increase the efficiency can produce a time reduction and as consequence a cost saving

Conventional technique Jetting & Drill-Ahead Drill 36” hole Run and cement 30” CP Drill 26” hole 20” csg Jet 30” CP and drill 26” hole Run and cement 20”csg

Deep Water Dual Casing Traditional techniques – CONSTRAINS: uncertainty about the formation to cross perfect verticality of WH and correct stick up not granted Deep Water Dual Casing

Conventional technique Jetting & Drill-Ahead Deep Water Dual Casing Drill 36” hole Run and cement 30” CP Drill 26” hole 20” csg Jet 30” CP and drill 26”or 23” Run and cement 20”csg Drill 23” x 36” hole with HO in tandem Run and cement 30” CP and 20” csg 1 jetting phase 1 drilling phase 1 cementing job 2 round trips 2 drilling phases 2 cementing jobs 4 round trips 1 drilling phase 1 cementing job 2 round trips

by using straight hole drilling device and motor No Rotation by using straight hole drilling device and motor

Drill 23” or 17 1/2” hole Start Rotation for 42” or 36” Hole

approximately 0° (zero degree) Drill 23”or 17 1/2” hole + 42” or 36” hole With Rotation for 36”/42” Hole The hole inclination approximately 0° (zero degree)

End of 23” or 17-1/2” hole + 42” or 36” hole POOH

36” or 42” hole + 23” or 17 1/2” hole

Ready to Run: Combination 36” or 30” C.P. + 20” csg or 20”+13 3/8” Tapered csg

MS 700 Wellhead Systems Guidelineless Type Drilling System without Guide structure Cement Port Low-pressure Housing Lowered into Mud Mat Hydrate Gas Seals Shown with mud mat & ball valve

DA COMPLETARE Standard cement DeepCRETE Foam cement CART 18” 3/4 Housing 18” 3/4 Housing 30” Standard cement DeepCRETE Foam cement Mud Mat Casing 20” 36” Hole Conductor pipe 30” Casing 13 3/8” Inner string DP 5” 17 1/2” Hole

Case History ENI Angola 1 Job: 30”x20”x13 3/8” Casing 3/31/2017 Case History ENI Angola 1 Job: 30”x20”x13 3/8” Casing 2 Jobs: 30”x20” Casing Title 15

ANGOLA OFFSHORE – CASE HISTORY # 1: Standard cement WD: 1300 m; Sea-bed temperature: 4 °C Shallow water risk: no Cement job: 30” C.P.x 20” x 13 3/8” tapered combined string Lead slurry: 1.44sg (12ppg) LiteFIL Tail slurry: 1.90sg (15.9ppg) Displacement: no cement returns at seabed WOC: 13 hrs Slack-off: casing string unstable WOC: additional 6 hrs Slack-off: OK Top job: cement job performed to ensure cement to sea bed In two slides or less describe what lead up to the loss

ANGOLA OFFSHORE – CASE HISTORY # 2: DeepCRETE Cement WD: 500 m; Sea-bed temperature: 6 °C Shallow water risk: yes Cement job: 30” C.P. x 20” casing Lead slurry: 1.20sg (10ppg) DeepCRETE with D500 GASBLOK Tail slurry: 1.90sg (15.9ppg) with D500 GASBLOK Displacement: returns at seabed WOC: 15 hrs Slack-off: casing string 1 cm “sink” WOC: additional 3 hrs Slack-off: OK Top job: no top job performed In two slides or less describe what lead up to the loss

ANGOLA OFFSHORE – CASE HISTORY # 3: Foam Cement WD: 1070 m; Sea-bed temperature: 5 °C Shallow water risk: no Cement job: 30” C.P. x 20” casing Lead slurry: 1.25sg (10.4ppg) Foam cement Tail slurry: 1.90sg (15.9ppg) Displacement: partial returns at seabed WOC: 15 hrs Slack-off: OK Top job: no top job performed In two slides or less describe what lead up to the loss

Wellhead cut and retrieved Annulus 20” - 30” CART 18” 3/4 Housing 18” 3/4 Housing 30” Mud Mat Casing 20” 36” Hole Conductor pipe 30” Casing 13 3/8” Inner string DP 5” 17 1/2” Hole Wellhead cut and retrieved Annulus 20” - 30”

3 different options: M/U C.P. and surf. csg during flat time and hang up them on Moon Pool trolley M/U C.P. during flat time but surface casing on line after drilling tapered hole M/U C.P. and surf. csg on line after drilling tapered hole

Requirements for full application: VDL to load spud in materials Motion compensator capability Moon pool trolley capacity > (C.P.+surface csg+inner string) weight w/S.F. Distance moon pool – sea bed > lenght of surface casing

If all requirements are NOT fully satisfied: Partial time saving but all other advantages are exploited: no C.P. sinking can occur housing pre-fixed stick up and verticality near to 0° is granted applicability in all lithology types latch between LP and HPWH Housing performed at surface, ensuring mechanical structural integrity

Dual Activity rig:

Drill 8 ½” P.H. M/U 36” C.P. Run BOP Drill 23”x42” hole Run BOP Run Dual csg string Run BOP Cementing op.

Operating time during riserless phase (drilling pilot hole and running BOP not included)

Advantages: Constrain: Deep water Dual Casing, a patented technology, is the most efficiency alternative to conventional techniques. Advantages: Hole inclination approximately 0 deg Reduction of risk assessment in C.P. setting for unknown lithology No subsidence events Top Cement Job feasibility LP HSG and HP HSG latch performed at surface Time reduction Constrain: Water depth longer than surface casing setting depth (Reduction of system efficiency) Rig technical characteristics If shallow hazard phenomena imposes the use of 26” intermediate casing (36” LP HSG & CP)