This document discusses wellbore tortuosity, which refers to undulations or spiraling in a wellbore path. It notes that tortuosity is relevant to fields like medicine, geology, and drilling. The types of tortuosity include micro, meso, and macro, as well as 2D undulation and 3D spiraling. Claims of benefits from lower tortuosity include improved drilling performance, hole cleaning, casing running, and more. However, quantifying tortuosity is challenging and subjective. The document discusses using curvature and torsion measurements as well as elastic energy to quantify tortuosity in a more precise and standardized way. It concludes that while various indices provide a reference, quantification results are improved when considering

1. 1
Wellbore Tortuosity – Do we
need to worry about it?
Dr.Robello Samuel

2. Tortuosity related to..
 Medical field
– Arteries
– Retinal vessels
 Geology
– Ground water
 River
 Drilling
– Wellpaths
X
X X

3. Tortuosity related to..
 Wellbore undulation
 Wellbore oscillation
 Wellbore spiraling
 Wellbore smoothness
 Wellbore quality
 Wellbore profile energy

4. Types of Tortuosity
 Micro
 Meso
 Macro
 2D – undulation (sinusoidal)
 3D – spiral (helical)

5. Claimed benefits..
 Enhanced drilling performance!
– torque and drag – low tortuosity, friction
– weight transfer – ROP, friction
– vibration – ROP
 Improved hole cleaning!
– hole cleaning – gauge hole
 Ease of running casing!
 Better-quality logging tool response!
 Superior cement jobs!
 Smooth completion runs!

6. • Qualitative Prediction
• Subjective
• Weighting factors needed





 


S
T
H
D
log
DDI
 
bu
d
tq
cl R
R
R
R
TDI
log
TRI 




Drilling Difficulty Index
Mechanical Risk Index
Modified Mechanical Risk Index
Trajectory Risk Index
Tortuosity Index
Quantification

7. What is the shape of the wellpath?
 What are the assumptions?
 What is the required survey interval?
 What is the predetermined shape?
 What parameters are used to determine the shape?
 Is the shape same between all the survey intervals?

8. Vanishing Tortousities
The product EI, (= M/κ) called the flexural rigidity of the
pipe
The product GJ, called the torsional rigidity of the pipe
deflection


deflection


deflection



9. Wellbore Smoothness – Quantification: Pitfalls
• Low/high torque and drag values
• Lower/higher swab and surge values
• (fluid & mechanical forces are coupled)
• Low weight transfer calculations
• Decreased hole cleaning
• High friction and sideforce values
• Wrong friction factor calibration
• Higher casing wear estimation
• Higher stretch values and thereby positional error
• Higher fatigue calculations
• Overestimation of safety factors for casing design
• Lower estimation of reach
• Wrong calculation of packer setting forces
Wellbore quality based on openhole surveys for rest of the phases results in

10. Methodology for Correction - Theoretical
Curvature
Torsion measures the departure of the wellpath
from a plane, or how sharply wellpath turns
Curvature is the bend of the wellpath
2 2 2
sin
 
   
 
2
2 2
sin 1 cos
    

    
   
 
  
  
 
 
Use both curvature and torsion

11. Absolute Energy
Relative Energy
Energy
Elastic Energy of a thin beam - it is characterized by bending and twisting least
while passing through a given set of points.
   
 dx
x
x
E
0
2
2
 




 
 





















n
n
n
1
i
i
2
i
2
i
abs
D
D
D
E n
 
notor
)
abs
(
s
tor
)
abs
(
s
rel
s n
n
n
E
E
E 

Energy Based Approach

12. 0
5000
10000
15000
20000
-50.00 0.00 50.00 100.00 150.00 200.00 250.00
deg/100ft
Depth(ft)
DLS
Torsion
5.00 10.00
-5.00 15.00 25.00
20.00
Example

13. • No industry standard for quantification
• Various methods and indices provide some form of reference but
have to be used with caution
• Wellbore curvature and torsion at survey stations determine the
shape of a wellbore trajectory
• Energy based method is very simple to calculate
• Quantification results are more precise when the curvature and
torsion are synchronously involved over every course length.
Conclusions

14. 14
Thank You