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. Outline Field Location Design Requirements Approach Execution
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
Integrated Formation Evaluation
Conclusions 2

3. Oberan Field Location High Pressure and High Temperature Field
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 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 3

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 4

5. Lean Casing Profile Application
Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria
Lean Casing Profile Application
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 5

6. Eni - Circulating Device
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. 6

7. Pore Pressure Prediction
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 7

8. Pore Pressure Prediction
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 8

9. Pore Pressure Prediction
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
Robust real-time communication and workflow was established
All data was shared using real-time data transmission system to make timely and efficient decisions 9

10. Well Verticality Maintaining well verticality helps reduce departure
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
Well Name
Average ROP
Maximum Inclination
Total Depth
Oberan – 2
38 m/hr
0.26
4,479 mMD
Oberan – 1
5 m/hr
2.61
4,340 mMD 10

11. Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria
Formation Evaluation
Comprehensive Wireline Logging Program in 13.5” and ” 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 11

12. Formation Evaluation 10.625” Section:
Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria
Formation Evaluation
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 12

13. Formation Pressure and Sampling
Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria
Formation Pressure and Sampling
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 13

14. Formation Pressure and Sampling
Integrated Drilling and Logging Program Approach in HPHT Environment: Successful Drilling of Deepwater Oberan Field, Nigeria, ENI Deepest Well in Deep Offshore Nigeria
Formation Pressure and Sampling
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 14

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 – ˚C
Maximum Deviation – 1.18 ˚ 15

16. Conclusions Drilling performance on Oberan-2 was optimized using:
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 16