ENERGY WISE WORKSHOP 2003

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2 ENERGY WISE WORKSHOP 2003 TECHNOLOGY OPTIONS FOR DEEPWATER BRAZIL Small Bore Drilling Risers Offer Reduction in Drilling Costs By E. Lustosa, S. Hatton, D. Walters 2H Offshore

3 Background Drilling costs are a major component of total field development costs (up to 50%) Cost limits the number of wells that can drilled reduces number of finds Limited reservoir delineation Higher risk and higher cost development solutions Drilling risers have a significant impact on costs Hardware - $$$ Vessel interface - $$$ Operationally installation/retrieval - $$$ Historically drilling risers have not been a drilling design driver due to shallower water

4 Current Status Shallow water technology extrapolated by adding joints, buoyancy & tension Application of large bore casing programs, wellheads and completions Negative spiral Standardisation on 18-3/4in wellhead, subsea BOP and 21in riser Sledgehammer Approach Universal, safe, flexible BUT expensive Requirement for high spec high cost vessels due to high tensions, deckload and riser / BOP storage Long riser installations / retrieval Slow drilling rates for large bore casing programs and volume of cuttings to remove

5 Small Bore Riser For Deep Water Small bore lightweight riser (13-16in) High pressure with surface BOP stack Subsea Shut Off Device (SSOD) - Optional Efficient casing program Slim, slender or expanded Allows a 2 nd or 3 rd generation MODU to drill in deep water environments Further cost reductions

6 Well Bore Isolation and Safety DP Drilling Vessel 13-5/8in Surface BOP with 4 rams and 1 annular 13-5/8in SSOD with one ram 18-3/4in subsea BOP with 4 rams and 2 annular BOPs One Blind Shear Ram One Blind Shear Ram

7 Typical high pressure surface BOP small bore drilling riser layout and equipment

8 Benefits of Small Bore Approach Reduced riser tension and buoyancy volume Reduced riser and BOP cost Reduced deck load and storage area Faster riser installation and retrieval (x10) Eliminate kill, choke and booster line complexity Improved cutting transport Faster drilling (reduced hole size) Reduced consumables Reduced cuttings Better well control Improved BOP maintenance (surface accessible)

9 Surface BOP Riser Design Issues BOP and well control procedures Clashing between BOP and vessel moonpool Riser stroke and space out Wave and current loading on BOP BOP handling procedures Industry considers it to be less safe Important to monitor riser performance

10 What should be monitored? Riser Top Tension Ensure correct riser tension is maintained Riser Taper Joint Inclination Ensure minimal wear in areas of maximum curvature/stress, ie: drill string in contact with casing bore Vibration acceleration / amplitudes Back calculate VIV fatigue damage in expected critical areas Current In correlation with the VIV monitoring to assist in benchmarking the VIV fatigue damage

11 Methods of Data Logging Standalone data logging Data stored on a smart media disk and retrieve later Can be retrieved by ROV via handles/frames Downloaded onto PC for back analysis Cost effective method Can be supplied on a rental basis On-line acoustic linked monitoring & On-line hard-wired monitoring Real time monitoring with data viewed and stored on PC hard disc Real time software requirement and user interfaces More expensive system

12 2H Monitoring Sensors Tension via LVDT (Linear Voltage Differential Transformer) Tension via dedicated load cells mounted in a shackle Inclination via inclinometers (typically bi-axial) Vibration Via Accelerometers in one or more planes (typically tri-axial)

13 Recent High Pressure Drilling Riser Monitoring Contract Three main areas where monitored to asses the riser response and provide assistance whilst drilling Upper tapered stress joint Inclination monitoring Vibration monitoring Aircan (Above & Below) Vibration monitoring Lower Tapered stress joint Inclination monitoring

14 Lower Tapered Stress Joint Instrumentation On-line acoustic linked inclination monitoring indicating Riser curvature at the tapered stress joints Excessive vessel offsets Inclination/riser heading

15 Lower Tapered Stress Joint Instrumentation Hardware Consist Of: Super-duplex control pod containing Bi-axial inclination sensors Data processing unit High power battery pack Acoustic modem receiver/transmitter Heavy duty mounting frame Dunking Transducer Acoustic modem receiver/transmitter Manually controlled Self contained deployment winch

16 Upper Tapered Stress Joint Instrumentation On-line hard wired inclination and vibration monitoring indicating Riser curvature at the tapered stress joints Excessive vessel offsets Inclination/riser heading Riser vibration due to abnormal drilling operations

17 Upper Tapered Stress Joint Instrumentation Hardware Consist Of: Super-duplex control pod with Bi-axial inclination sensor Bi-axial acceleration sensors Data processing unit Subsea Wet mateable connectors Multi-core reinforced subsea cable with precision moulded connectors

18 On Deck Hard Wiring Interfaces A typical Hardwiring consist off: On deck flameproof double armoured multi-core cable. Zone 1 rated Explosion and flame proof junction boxes with flameproof cable glands All cables routed to a PC for data analysis

19 Aircan Vibration Monitoring (Standalone data loggers ) 2H Standalone Data Logger MKII Standalone data logging for vibration monitoring Low cost monitoring of the riser response for Vortex Induced Vibration (VIV) at the aircan Standalone loggers are easily deployed and retrieved Can be supplied on a rental basis

20 Typical On-line GUI The 2H software interface provides immediate assistance to the drilling engineer with visual displays and warning functions.

21 Data Output From GUI Inclination Vs. time, in X or Y for the logging period (degree s) Maximum reported inclination (degree s) Inclination heading (+/ from vessel bow) Maximum acceleration in X & Y for the logging period (RMS m/s 2 ) Battery pack voltage (acoustics only) Assistance to the drilling engineer. If any value goes above the pre-set limits the engineer will make the decision to stop drilling.

22 Typical Logging Period, Online and Standalone Continuous logging requires vast amounts of battery power and is not usually necessary Periodic monitoring is usually employed, typical logging period may consist off: Logging for 15mins every hour at a frequency of 10Hz. Continuous logging is only required for extreme conditions, Environmental Abnormal drilling conditions

23 Summary High Pressure Drilling Risers offer many benefits, resulting in large cost savings Key concern is reliability and safety A good riser monitoring system will provide data to assist the drilling engineer in providing assurance of safe operation Variety of monitoring systems available to monitor all aspects of the riser response Motion, angles, tension, temperature.. Need to plan for implementation of hard wired and acoustic systems No need to plan for standalone systems (currently limited to motion only, VIV response)