DRILLING FLUID CHALLENGES FOR

OIL-WELL DEEP DRILLING

Vassilios C. KELESSIDIS

Technical University of Crete

Mineral Resources Engineering

SGEM 2009

Albena, June 14-19, 2009

Research aim

�Develop smart drilling fluids

�Adaptable to harsh conditions

�Have available techniques for optimal

measurements of fluid properties, particularly

rheologyrheology

�Develop hydraulics models for pressure drop

prediction along the wellbore

�Better understanding efficient cuttings

transport in a multiphase environment

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The problem

�Drilling depths, total (>7000 m) and water (~ 3000m) depths, are ever increasing

�High pressures (>2000 bar) and high temperatures (>3000C) are encountered

�Narrow pressure tolerances

Harder rock is encountered, lower drilling �Harder rock is encountered, lower drilling rates

�Demand for better drilling fluids, avoid problems -understand behavior in such hostile environments

�Hydraulic programs for complex rheology

33

Deep drilling challenges

44hard rock - wellbore stability - high P, T

MPD vs Conventional

55

Drilling fluid challenges

ROLE

�Hydrostatic pressure

�Cuttings transport

�Cooling the bit

�Wellbore stability�Wellbore stability

CHALLENGES

�High T,P � stable density and rheology

�Measurements at downhole conditions

� Predictions of downhole conditions

�Stability of additives

�Appropriate rheological models66

Rheology, effect of pressure and temperature

Low T

77

High T

Lignite additive for T control

88

‘Flat’ rheology fluids

99

Barite sag – solution ?

841.0

*116.0

85.4

=

=

=

n

sPaK

Pa

bariteAPI

yτ

854.0

*076.0

92.0

=

=

=

n

sPaK

Pa

baritesizedmicron

yτ

Rheograms for micron sized barite

1010

Conclusions

�Demand for more energy � challenge to oil industry, deeper waters and deeper wells

�Extreme environments � better drilling fluids

� Improved drilling techniques, Managed � Improved drilling techniques, Managed Pressure Drilling, narrow pressure margins

�Good and representative rheological models for the complex fluids

�Model of choice – Herschel-Bulkley, hydraulics modeling is needed

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Conclusions�Take into account effects of temperature and

pressure

�Modeling for predicting temperature and

pressure downhole

�Rheological measurements at downhole �Rheological measurements at downhole

conditions

�Development of additives that withstand

extreme conditions

� Leading to ‘smart’ drilling fluids, adopting to

particular environment1212

Need to meet the challenge

1313