Page 242 - Drilling Technology in Nontechnical Language

Chapter 10 – EVALUATION 233

A fully computerized unit with readout screens in the drilling

supervisor’s office is now the norm. It is also possible to transmit this

information in real time to the office, where further analysis can be
done. With experienced engineers providing round-the-clock cover while
drilling, warnings can be provided to the drillers of impending problems
(such as pore pressure increases or wellbore instability).

The unit computers record a range of parameters relative to time and
depth, and at the end of the well, these are handed over electronically to the
operator. Typical recordings will be made of the following:
▪ Depth in feet or meter intervals

▪ Drilling rate, both minutes per foot (meter) and feet (meters)
per hour
▪ Weight on bit

▪ Rotary speed
▪ Rotary torque
▪ Pump output

▪ Pump pressure
▪ Mud density being pumped into the well and returning from
the annulus
▪ Mud temperature in and out
▪ Levels of gas dissolved or present in the mud returning from
the annulus.
If problems are encountered (such as stuck pipe or a break in the
drillstring), this recorded data is very useful in helping to determine the
root causes of the problem. Only by knowing the root causes can a strategy
be developed to solve the problem and avoid a future recurrence.

Physical Sampling Down Hole

Coring is the act of retrieving a whole sample of the downhole
formations for analysis at the surface. Several classifications of coring can

be made, such as the following:
▪ Bottomhole coring

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