Developing smart drilling fluids that can adapt to harsh downhole conditions with extreme pressures and temperatures over 7,000 meters deep is challenging. Drilling fluid must maintain stable density and rheology at these conditions while transporting cuttings and cooling drill bits. Improved rheological models and hydraulics modeling are needed to better predict downhole pressure and optimize fluid properties. Additives also need to be developed that can withstand the hostile environments encountered during deep drilling.

1. DRILLING FLUID CHALLENGES FOR
OIL-WELL DEEP DRILLING
Vassilios C. KELESSIDIS
vaskel1@hotmail.com
sk l1@h tm il m
Technical University of Crete
Mineral Resources Engineering
SGEM 2009
Albena, June 14-19, 2009

2. Research aim
Develop smart drilling fluids
Adaptable to harsh conditions
Have available t h i
H il bl techniques for optimal
sf ti l
measurements of fluid properties, particularly
rheology
Develop hydraulics models for pressure drop
prediction along the wellbore
Better understanding efficient cuttings
transport in a multiphase environment
2

3. The problem
Drilling depths, total (>7000 m) and water (~
3000m) depths, are ever increasing
depths
High pressures (>2000 bar) and high
temperatures (>3000C) are encountered
Narrow pressure tolerances
Harder rock is encountered, lower drilling
rates
Demand for better drilling fluids, avoid
p
problems -understand behavior in such hostile
m
environments
Hydraulic programs for complex rheology
3

4. Deep drilling challenges
hard rock - wellbore stability - high P, T 4

5. MPD vs Conventional
5

6. Drilling fluid challenges
ROLE
Hydrostatic pressure
Cuttings transport
Cooling the bit
Wellbore stability
stab l ty
CHALLENGES
High T P
T,P stable density and rheology
Measurements at downhole conditions
Predictions of downhole conditions
Stability of additives
y f
Appropriate rheological models 6

7. Rheology, effect of pressure and
temperature
Low T
High T
7

8. Lignite additive for T control
8

9. ‘Flat’ rheology fluids
9

10. Barite sag – solution ?
Rheograms for micron sized barite
API barite micron sized barite
τ y = 4 . 85 Pa τ y = 0.92 Pa
K = 0 . 116 Pa * s = 0.076 Pa * s
K
n = 0 . 841 n = 0.854
10

11. Conclusions
Demand for more energy challenge to oil
industry, deeper waters and deeper wells
Extreme env ronments
environments better drilling
dr ll ng
fluids
Improved drilling techniques Managed
techniques,
Pressure Drilling, narrow pressure margins
Good and representative rheological models
for the complex fluids
p
Model of choice – Herschel-Bulkley,
hydraulics modeling is needed
11

12. Conclusions
Take into account effects of temperature and
pressure
Modeling for predicting temperature and
pressure downhole
Rheological measurements at downhole
conditions
Development of additives that withstand
extreme conditions
Leading to ‘smart’ drilling fluids, adopting to
particular environment
ti l i t
12

13. Need to meet the challenge
13