Page 138 - Practical Well Planning and Drilling Manual

Section 1 revised 11/00/bc 1/17/01 2:56 PM Page 114

[ ] Well Design
1.5.2

very high wear rate will quickly become moderate; abrasive wear will
decrease as the tong marks on the pipe are worn down and contact
pressure drops. After a trip there will tend to be a temporary increase
in wear because new tong marks will be present.
The hard banding on tool joints is very important. It must be
smooth, hard, and flush with the tool joint. In the “old days” hard
banding could be very rough and stood proud of the tool joint—an
efficient rotary file. If it is not flush then all of the lateral force is taken
on that small area so that contact pressure is extremely high. Never run
rough hardbanded tool joints inside casing while drilling.
Dull tong dies will tend to make marks worse on the tool joints as
more closing pressure is required to make these dies grip. Apart from
the safety aspect of slipping tongs, using dull dies is false economy. Slip
and tong dies should be inspected after every round trip and replaced
as soon as they become worn.
Casing wear should be monitored by placing two ditch magnets in
the return mud flowline or possum belly tank. At the same time each
day (usually midnight) the magnets are cleaned off and the metal
recovered. Make sure that the mud particles and crud adhering to the
metal is removed and then weigh the sample. The daily drilling report
should note the daily and cumulative amounts of metal in lbs or kgs.
Any sudden increase in the return metal trend should be investigated.
Examination of the metal from the ditch magnet should indicate which
kind of wear is taking place.
Lubinski proposed a limit of 2000 lbs of contact force, below
which damage to tool joints would not be substantial (as discussed
above). Wear rates should be moderate below this limit using solids-
weighted mud, with smooth hardfacing that is level with the rest of
the tool joint OD, and using sharp-tong dies, wear rates should be
moderate. Use protectors to reduce lateral forces as described above to
below this limit.
If a solids-free mud or brine system is used then wear rates will
be much higher. Extra precautions in this case may include using
nonrotating protectors (i.e., free to rotate on the drillstring), down-
hole motors (to minimize rotating the drillstring), minimizing the
dogleg severities and running heavier wall casing over the build and
below the wellhead.

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