Slickline is more
commonly used in production tubing. The wireline operator monitors at surface
the slickline tension via a weight indicator gauge and the depth via a depth
counter 'zeroed' from surface, lowers the downhole tool to the proper depth,
completes the job by manipulating the downhole tool mechanically, checks to
make sure it worked if possible, and pulls the tool back out by winding the
slickline back onto the drum it was spooled from. The slickline drum is
controlled by a hydraulic pump, which in turn is controlled by the 'slickline
operator'.
Slickline comes in different sizes and grades. The larger
the size, and higher the grade, generally means the higher line tension can be
pulled before the line snaps at the weakest spot and causes a costly 'fishing'
job. Due to downhole tools getting stuck because of malfunctions or 'downhole
conditions' including sand, scale, salt, asphaltenes, and other well byproducts
settling or loosening off the pipe walls because of agitation either by the
downhole tools or a change in downhole inflow, sometimes it is necessary to
pull hard on the tools to bring them back uphole to surface. If the tools are
stuck, and the operator pulls too hard, the line will snap or pull apart at the
weakest spot, which is generally closer to surface as the further uphole the
weak point in the line is, the more weight it has to support (the weight of the
line).
Weak spots in the line can be caused by making the circle around
the counter wheel, making a bend around a sheave, a kink in a line from normal
use (when rigging up the equipment extra line must be pulled out from the truck
to give enough slack when the pressure control lubricator is picked up - this
leaves line coiled on the often rutted ground, and sometimes it snags and kinks
the line).
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