This document discusses downhole problems that can occur while drilling wells and methods to prevent them. It covers various downhole problems like pipe sticking, pipe failure, dog legs, key seats, shale problems, and lost circulation. Pipe sticking can be mechanical or differential. Dog legs occur from changes in formation dip or bit weight. Key seats form from doglegs. Shale problems include hole enlargement, caving, sloughing, and heaving. Lost circulation happens when mud pressure exceeds formation pressure. Prevention methods include using inhibitive muds, slowing drill string movement, and drilling with low pump pressure and fluid velocity. Faster drilling can mitigate many downhole problems by reducing shale exposure time and mud costs.

1. Submitted To :
Dr. Md. Aminul Islam
Assistant Professor,
Dept. of Petroleum &
Mining Engineering
Jessore university of Science
& Technology
Submitted By :
S.M. Samiur Sany
Roll : 140802
Session : 2014-15
Dept. of PME,JUST
Jessore University of Science And Technology
Welcome To My
Presentation On
Down Holes Problems
And Their Prevention

2. Contents :
 Down holes problems
 Pipe Sticking and their types
 Pipe Failure
 Dog legs and telescopic holes
 Key seats in holes
 Shale problems
 Lost circulation
 Precautionary measure to avoid down hole problems

3. Down hole problems
 It is almost certain that problems will occur while drilling a well,
even in very carefully planned wells such problems that obstruct
drilling are called down hole
problems.
 The main reasons behind this problems are when two wells near
each other may have totally different geological conditions and in
areas where similar drilling practices are used.
 In well planning we should keep in mind that the key to achieving
objectives successfully is to design drilling programs on the basis
of anticipation of potential hole problems rather than on caution
and containment as drilling problems can be very costly.
 Understanding and anticipating drilling problems, understanding
their causes, and planning solutions are necessary for overall-well-
cost control and for successfully reaching the target zone.

4. Types of down hole problems :
 Pipe Sticking
 Pipe Failure
 Dog legs and telescopic holes
 Key seats in the holes
 Shale problems
 Lost circulation
 Bore hole instability
 Mud contamination
 Formation damage and
 Hole cleaning

5. • Pipe sticking :
 Pipe is most common trouble during
drilling a well in pipe . It is more serious
and expensive while drilling deep high
pressure wells.
 Causes behind this problem
- Encountered during drilling an
unconsolidated formations
- Insufficient hydrostatic to hold back
formation.
 Classifications :
-Mechanical sticking
-Differential sticking
-Formation related sticking
 Only mechanical pipe sticking are
addressed in this presentation.
Preventions :
-Increases in torque and drag
-Excessive cuttings loading
-Tight spots while tripping
- Loss of Circulation during drilling

6. The following conditions are
responsible for mechanical
pipe sticking as -
-Distorted well bore
geometry
- Under gauge hole
-Poor hole cleaning
-Key seating
-Junk in the hole
-Cement related problems
-Collapsed casing
Mechanical pipe sticking :

7. Pipe Failure :
 Drill pipe failures is a prevalent
drilling problem appeared during
drilling.
 Sometimes drill pipe fails from its
tool joint and drill collars fails
from its connection.
 Approximately 50% of the fishing
jib occurs on account of tool joint
failure.
 Causes :
- Swelling of connection box
- Improper tightening of
connection.
-Improper initial making up-of
connection

8. Dog legs :
 A dogleg is usually defined as any
deviation greater than 3° per 100 ft.
 It occurs when a sharp change of
direction is taken in the wellbore.
 Typically, a dogleg is caused by a
change in the dip of the formation or
by a change in the weight applied to
the bit.
 Severe doglegs can result in stuck
casing, drill pipe failure, and inability
to run casing to total depth.
Indications of dog leg in a hole :
 Unable to log the well.
 Unable to run the pipe.
 Excessive casing wear.
 Excessive drag.

9. Key Seats in hole :
 Key seats usually form as a result of
dog legs.
 A key seat is formed when a channel
or groove is cut in the side of the
hole, parallel to the axis of the hole.
 In very hard and soft formations, key
seats do not form as they collapse in
very soft formation.
 Key seats only takes place in the
medium hard formation.
Prevention :
 Key seat can be prevented by not
creating doglegs.
 Blasting of explosive charge in very
small scale can destroy key seats.

10. Shale problems :
 Shale problem is one of the
complex trouble encountered
during drilling.
 There are several types of shale
problem that happens depending
largely on shale hydration, swelling,
dispersion of shale amd exposure
time of shale.
 The following problems are
generally encountered while drilling
shale section –
• Hole enlargement
• Caving
• Sloughing
• Heaving
• Hole cleaning
• Mud cake
Origin of shale problem :
 Related to physic-chemical
absorption of water , based
on Surface HC of clays ,
migration of water into clays
by osmosis.
 Related to mechanical
stresses
 Overburden pressure
 Pressure surges
 Tectonic stresses
 High dips
Remedial measures:
 Inhibitive mud can be used to
avoid this problem.
 Slow movement of drill string.
 Drilling with low pump pressure,
Low fluid velocity and low rotary rpm

11. Lost circulation :
 Lost circulation is the complete or
partial loss of drilling mud into a
formation.
 The loss occurs when the total
pressure exerted against the formation
exceeds the total pressure of the
formation.
 Lost circulation results in increased
mud expense and may cause
subsurface blowouts.
 The proper drilling fluids and use of
lost circulation material will minimize
lost circulation.

12. Precautionary measure to avoid down hole
problems :
 Drilling specialist claims that faster drilling can mitigate almost all the
down hole problems and the following advantages can be derived from
it-
- Reduced exposure time for troublesome shale
- Lower mud cost
- Fewer casing strings
- smaller diameter leads to greater stability

13. Thanks everyone