Prevention and monitoring
• Cleaning the Hole
• Torque and drag
• Hints of pipe glue – clippings and landslides
• Drilling Parameters
* Hole Cleaning
In high-angle wells, 80% of pipe-glue events are due to hole
cleaning
Achieving good cleaning of the hole is the key to preventing
non-productive times (NPT) and associated cost (red money) caused by the pipe
sticking in the well
• Vertical Wells Vs. Directional Wells
-Used hole cleaning techniques are effective depending
mainly on the angle of the well section.
-The cleaning parameters in the vertical sections are
different from those used in the horizontal sections.
-The cleaning of the hole becomes more critical in the
sections with angles between 30 and 60 degrees of inclination.
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Piping Stress Analysis Services |
During drilling, the velocity of the fluid must be strong
enough to counteract the effects of gravity, which will make the clippings fall
to the bottom of the well. Usually this speed is reached efficiently in the
vertical wells, fulfilling well the task of cleaning the hole.
However, in Direcccionales wells present this problem with
greater difficulty. Under the influence of gravity, the clippings will try, but
because of the inclination of the well, they do not have to fall far to reach
the lower part of the well wall. In this situation, the velocity of the
drilling fluid should be higher even in order to keep the clippings going up to
the surface.
For a certain inclination of the well will occur a rapid
settlement of individual particles in a bed of clippings already existing in
the lower part of the well
Once the critical mass has accumulated the particles can
slide down the annular very quickly
Conveyer Bar Concept
• Proper use of mud pills can improve hole cleaning in vertical
and directional wells.
• High viscosity (preferably heavy) pills are often
effective in holes greater than 8 ½ "while low viscosity pills are
effective in smaller holes.
• Pumping low viscosity pills followed by a high viscosity
(heavy) pill ensures proper hole cleaning in large diameter wells in vertical
well sections.
• Combining pills with string rotation improves hole
cleaning
• The specific volume of the pills should be determined
based on the diameter of the hole and the calculation of the hydrostatic
column.
• Pumped pills have to be carefully monitored and the
returns of clippings need to be assessed
String rotation
The rotation of the string:
Increases flow velocity in hole walls
Keeps cuts off the walls (speed and mechanical strength effects)
contributes more as the angle of the well increases
* TORQUE and drag
Increases in Torque and drag trends are indicators of hole
problems, such as:
Increase in hole clippings
Hole stability Problems
Tight hole conditions
Tortuosity in the Hole
Drilling equipment problems
Widened hole by erosion ("washouts")
Why monitor Torque and drag variations?
• Evaluate hole deterioration and problems related to well
stability
• Check the cleaning efficiency of the hole by circulating
in each connection, circulating overhead, bump pumping, calibration trips, etc.
• Detect the formation of clipping beds (combined with DEC,
removal of clippings in vibrating nets, etc.)
• Identify torque problems and equipment limitation.
• Finding mud-lubricating capacity failures plus the effects
of sludge weight and changes in their properties.
• Define the friction factors for each well and build a data
base of friction factors for multiple wells, both for open holes and for coated
holes.
• Understand the effects of training.
• Identify changes in angles of inclination and direction –
through construction sequences, spinning, laying down, maintaining angles in
certain portions of the well.
• Anticipate well problems that affect the run of the liner.
When to monitor?
• On each connection
• While traveling down and out of the hole, especially in
open sections.
• After considerable changes in inclination and direction.
• Before, during and after calibration trips.
• Before and after circulating backgrounds and pumping
potholes.
• With the auger inside the liner, before drilling out/back
into the open hole.
• After an increase/decrease in the weight of the sludge,
change of type of sludge or considerable changes in the rheology of the same.
• At full depth after the hole has been cleaned.
• Before and after adding torque reducers such as
non-rotating lubricants and pipe protectors etc.
* Hints of pipe glue
Surface Condition and parameter analysis
* Analysis of cuts and landslides
Landslides:
They are fragments of rock caused by the instability of the
hole that are transported to the surface by the drilling fluid
Typically landslides are 1 to 2 centimeters long, but their
dimensions may vary from millimeters to 10 centimeters or more.
Utility for the analysis of landslides
are an alarm signal about the instability of the hole
They allow to deduce which formations are unstable
Its geometry is an indicator of the fault mechanism
Allow you to define a remedial action