1

The Importance of Dynamic ECD and Well Control Models in Advanced Drilling

Inge Mosti, Bjørn-Tore Anfinsen, Petter MathisenSPT Group

IQPC HPHT Wells Summit 2008, Aberdeen

November 25th 2008

2

Overview

• New drilling challenges

• Important physical models

• Dynamic effects related to decreasing operational margins

• Case studies illustrating dynamic effects

• Conclusions

3

Advanced Operations

4

Challenges

• Technically Complex operations– Costly rig downtime

• Narrow margins – Downhole ECD management– Know the effect of operational changes– Gel breaking and Surge&Swab

• Low tolerance for kicks– Requires accurate and realistic planning– Impact from thermal expansion

• Extreme temperature variations– Thermal expansion– Downhole tool failure

5

How can these challenges be addressed?

• Improved planning using dynamic models– Training

• Active use of software models in operational follow-up

• New drilling techniques– Managed Pressure Drilling– Dual gradient

Dynamic software models that includethermal effects are required

6

WorkflowWell integrityOperational

limitations

UnderstandingPreparedness

Model Calibration Operational updateDecision making

Lesson learnedImprovement

Planning

Post analysis

Training

Execution

Dynamic Model

Dynamic Model

Dynamic Model

Dynamic Model

7

8

Temperature variations

9

Pit gain from thermal expansion

10

ESD variation due to temperature

2 points reduction

11

Gel effect when breaking circulation

500 1000 2000 2500200

12

Gel effect on surge pressure

13

Undetected kick in deep water riser

0.8 m3 influx at connection

No pit gain indicating a kick during circulation

BOP

14

Undetected kick in deep water riser

Gas breakout at ~300m

BOPRapid pit gain due to gas expansion

Secondary kick due to reduction in bottom hole pressure

Bottomhole pressure reduction

How much drawdown in bottom hole pressure can be expected from a given influx volume

17

Undetected kick in deep water riser

• Argument for WBM?

Gas front position at BOP

Can you detect the difference?

WBM OBM

18

Case study #1

StatoilHydro – Tulipan (Tulip)

– Exploration well in the Norwegian Sea– Water depth: 1260 m– 9 5/8” casing shoe at 3840 m– Drilling 8 ½” from 3965 to 4230 m– Circulation rate 2000 – 2500 lpm– RPM=60-180– Torque=4-13 kNm– Water based mud 1.56 sg

19

Simulation procedure

• Post analysis– Steady state tool originally used gave inaccurate results

• Operational data entered into the simulator

• Performed as a “blind test” – downhole data freed by company after simulation results were delivered

20

Flowrate and pump pressure

Good match between simulated and measured pump pressure over the interval (within 10 % of measured values)

21

Temperature while drilling ~ 250 m

Simulated bit depth temperature within 3-5 deg C.

Main trends of simulations are following measurements.

22

ECD while drilling ~ 250 m

ECD at bit is within 0.01 sg(0.08 ppg)

23

Results case study #1

• The simulator reproduces downhole ECD and temperature data over a long drilling interval

• Both ECD and temperature are within an acceptable range of the measured data

• The simulator gives information about well conditions when downhole data is unavailable

24

Conclusions

• Advanced operations require detailed planning– Large thermal effects

– Good knowledge of ECD contributions

• Include thermal pressure build-up effects in kick tolerance considerations

• Understand how the well responds to operational changes

• Dynamic modeling is valuable in tight margin wells

Acknowledgements

We would like to thank

StatoilHydro

for the permission to publish field data

26

Conclusions

• Advanced operations require detailed planning– Large thermal effects

– Good knowledge of ECD contributions

• Include thermal pressure build-up effects in kick tolerance considerations

• Understand how the well responds to operational changes

• Dynamic modeling is valuable in tight margin wells

27

be dynamic

www.sptgroup.com