Page 92 - Drilling Technology in Nontechnical Language

Chapter 3 – DRILLING A LAND EXPLORATION WELL 83

Killing the well after the production test is complete

Once the well test is over, the well will be “live” from the pressure

inside the tubing. The well is “killed” by pumping heavy fluid down the
tubing, which will build up enough hydrostatic pressure to overcome
the reservoir pressure. Once the well is completely dead, the well can
be abandoned.

Abandoning the Well

A well is abandoned when there is no conceivable use for it after the
well test. Well abandonment involves placing cement in the well to prevent

reservoir fluids leaving the reservoir and moving up towards the surface.

Removing the test string

Once the well is dead, plugs are placed inside the tubing to ensure that,
even if pressure does start to build up inside the tubing, nothing can come
back to the surface. The Christmas tree can then be removed and the BOP
nippled up on top of the tubinghead spool.
The bolts holding the tubing hanger in place are removed, and the test
string can be pulled out.

Making the well safe into the future

The first task is to run in with some pipe and pump cement down so
that it is left around the perforations. Often, special plugs will be run on
wireline electric line to give additional security.

Special cutting tools are available that can cut the casing. The casings
will be cut above the top of cement outside the casing so that the upper bit
of casing can be pulled out of the well. Finally the conductor is cut, cement
is dumped on top, and the site is restored for future nondrilling use.

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