Page 264 - Drilling Technology in Nontechnical Language
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11
WELL CONTROL
Overview
The principles of hydrostatic pressure were described in detail at the
end of chapter 1. Also mentioned was the result of drilling into a formation
where the pore pressure exceeded mud hydrostatic pressure—a kick may
occur, where formation pore fluids enter the wellbore.
This chapter will define well control (primary, secondary, and tertiary).
The processes and equipment involved in kick detection and control will
be described. Special well control situations (shallow gas, kicks and losses,
blowouts, high-pressure, high-temperature wells, and underbalanced
drilling) will also be discussed in sufficient detail to impart a basic
understanding of the causes, effects, and implications.
Primary, Secondary, and Tertiary Well Control
The term well control refers to the control of downhole formation
pressures penetrated by the well. There are three distinct well control
levels that may occur during drilling operations.
Primary well control
The first line of defense is primary well control, which results
from maintaining the density of the drilling fluid such that hydrostatic
pressure at all depths where formations are exposed exceeds formation
pore pressures:
Mud hydrostatic pressure > Formation pore pressure
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