Page 60 - Drilling Technology in Nontechnical Language

Chapter 3 – DRILLING A LAND EXPLORATION WELL 51

Coring program

In an exploration well, it is very likely that interesting formations
(those with reservoir potential) are cored. In this process, a special drill bit
is used that cuts a doughnut shape, leaving a column of formation sticking
up the middle. Behind the bit is a barrel (called a core barrel) that contains
this core and recovers it to surface.

Well completion design

In order to design the well, the engineers need to know how the
well will be completed, and in particular, the size (outside diameter) of
the completion or test tubing string. As this is an exploration well, the

well will use a test string, and the size of test string can be specified at
this time.

Well test information

If the well discovers hydrocarbons, a test program will be written.

Although the final test program cannot be known until the hole is logged,
it is known in general what the program will involve and what testing
equipment will be needed. The equipment has to be arranged in advance and
should be available to send to the rig as soon as a well test is confirmed.

Status of the well when the rig has nished work

In the case of this example exploration well on land, the well will
be abandoned after testing. In the case of other types of wells (such as a
producing development well), the drilling engineers need to know what

should be the status of the well when they finish their work. It could be
left unperforated, or it could be perforated and then killed with clean
completion fluid, or something else.

It is normal to include a diagram illustrating the final well status.
Figure 3–8 is a well drilled offshore West Africa.

_Devereux_Book.indb 51 1/16/12 2:06 PM