Page 74 - 4925

tool on the bottom of the drill stem then lowers the tool to the bottom of the hole. The
crew applies weight to the tool to expand a hard-rubber sealing element called a
packer. The expanded packer seals the hole above the packer. The DST crew then
opens ports in the tool that lie below the packer. Opening the ports exposes recorders
to pressure. Analysis of the downhole pressures indicates whether the well can
produce.

Coring

In some cases, the operator may wish to examine directly a formation sample
that is larger than the cuttings. If so, a core sample is ordered. Two coring methods
are available. In one, the drilling crew makes up a core barrel and runs it to bottom.
When the driller rotates the core barrel, it cuts a cylinder, or core, of rock. The core is
often several inches (or millimetres) in diameter and several feet (or metres) long. As
the core barrel cuts the core, the core moves into a tube in the barrel. After the desired
length of core is cut, the crew trips out the drill string and the core barrel. At the
surface, the core is removed and shipped to a laboratory for thorough analysis. The
second coring method uses a sidewall sampler. In this method, the crew lowers the
sampling device to the desired depth. The driller actuates a switch to make the
sampler fire an explosive charge. The explosion rams several small cylinders into the
wall of the hole. Wires on the cylinders keep them attached to the sampler. Then
when the crew retrieves the sampler, the cylinders, along with bits of the formation,
follow the sampler to the surface. Sidewall samplers can obtain up to thirty small
samples from any depth.

4 Find synonyms in the text for the following words.
domain affirm
abundant discontinue
inancing precise.

5 Find antonyms in the text for the following words.
center destruction
withhold hide
inappropriate inaccurate.

6 Say whether the following statements are true or false.
1 Formationevaluation includes the activities the operator does to test a
formation for sulfur.
2 Methods of formation evaluation include examining cuttings and
drilling mud, well logging, drill stem testing, and coring.
3 Examining cuttings is a technique which helps the operator decide
whether to complete the well.
4 The function of a mud logger is to spot hydrocarbonsin the drilling
mud.
5 The logging tools cannot transmit the data they gather to the truck or
logging shack.

73