Field Location Design Requirements Approach Lean Casing Profile Application

1. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria

2. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Outline • Field Location • Design Requirements • Approach • Lean Casing Profile Application • Pore Pressure Prediction • Well Verticality • Formation Evaluation • Execution • Pore Pressure Prediction and Mud Weight Management using LWD Sonic and Resistivity while drilling • Well Verticality • Integrated Formation Evaluation • Conclusions

3. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Oberan Field Location • High Pressure and High Temperature Field • High Pressure (~ 10,800 psia) • High Temperature (~157 degC extrapolated SBHT @ TD) • Oberan-2 • Exploration/Appraisal Well 80 km from coastline in 674m water depth • Test and characterize deep section of anticline structure in equivalent Miocene Bonga Clastic sequence • Planned TD to 4,479 mMD with lean casing profile • Need a picture of Oberan Field

4. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Design Requirements • 1. Each section should be drilled to maximum possible depth • Pore Pressure Prediction and Well Verticality • 2. Casing seat point should be set in sand based on criteria of maximum kick tolerance • Lean Casing Profile Application • Mud Weight Management • 3. Detailed evaluation of all geological targets should be done. • Gas, clays, radioactive minerals and complex lithology

5. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria • Closed loop system to help drill and case well at reduced time and cost • Consolidated technology keeping the same production casing and reducing diameters of surface and intermediate casings • Better rate of penetration due to smaller hole diameter • Reduced cutting volumes, improved hole cleaning and controlled annular pressure losses • Reduction of annular clearances requires closer monitoring of all aspects of operation Lean Casing Profile Application

6. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Eni - Circulating Device • Combined with LWD annular pressure tool ensured effective pore pressure and shock management • Each well section was drilled to maximum depth allowing real time decision in setting casing points. Each section should be drilled to maximum possible depth • Eni patented Circulating Device was used to effectively manage mud weight within narrow margin between fracture gradient and pore pressure.

7. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Pore Pressure Prediction • Help increase and optimize borehole stability • Failure to maintain mud weight within hydraulic operating range can compromise setting deeper casing points • LWD sonic data was primary in under compaction model because less affected by temperature and salinity • LWD Resistivity data was used in hole sections where sonic data was unavailable

8. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Pore Pressure Prediction • Pre-Drill Model was created using interval velocity from surface seismic and offset well data of Oberan-1 • High quality real-time sonic and resistivity data enabler for pore pressure prediction model update. Model was calibrated using data from Wireline formation tester for the section completed to have revised model for next section • Leak off test at the start of each section provided critical calibration point

9. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria • Robust real-time communication and workflow was established • All data was shared using real-time data transmission system to make timely and efficient decisions Pore Pressure Prediction

10. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Well Verticality • Maintaining well verticality helps reduce departure • Less total drilling length helps reduce risks and costs in high pressure high temperature environment • Automated Vertical Rotary Steerable System (RSS) was used to maintain verticality • RSS helps in mud weight management and borehole quality through continuous rotating

11. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria • Comprehensive Wireline Logging Program in 13.5” and 10.625” open hole well section • 13.5” Section: • High Resolution platform express and LWD resistivity for fast and robust results • Dipole Shear Imager tool was run for compressional and shear acquisition Formation Evaluation

12. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria • 10.625” Section: • Accelerator Porosity tool was run to acquired epithermal neutron measurement for lithology evaluation and gas detection • High Resolution Gamma Ray Spectral Measurement assisted in clay typing and volume indications • Petrophysical information collected was key for MDT operations Formation Evaluation

13. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria • Modular Dynamic Formation Tester was run in 3 well sections • 141 pretest acquired and 85 reliable pressure points • Several downhole fluid analysis and sampling stations were performed • Fully characterize hydrocarbon bearing zones and aquifers Formation Pressure and Sampling

14. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria • Some sampling stations used focused technique (Quick Silver Probe) • Allows to capture contaminated fluid and discharge into wellbore and direct clean fluid to fluid analyzers and sampling bottles Formation Pressure and Sampling

15. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Well Performance • Oberan-2 was drilled to target TD without having to use last planned casing string • Total Depth – 4,479 mMD • Maximum Pressure Recorded - 10,800 psi • Maximum Temperature Recorded – 153.3 ˚C • Maximum Deviation – 1.18 ˚

16. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria Conclusions • Drilling performance on Oberan-2 was optimized using: • Intelligent fit for purpose new technologies • Risks and challenges were assessed in planning stage to safely achieve well targets • Drilling technologies including automated rotary steerable system, lean profile application, eni circulating device and real-time pore pressure helped: • To set deeper casing points • To maintain well verticality • To increase ROP by drilling close to balance and no sliding • To ensure safer drilling practices