文档介绍：Drilling Muds
Drilling fluids are mixtures of natural and synthetic chemical compounds used
to cool and lubricate the drill bit, clean the hole bottom, carry cuttings to
the surface, control formation pressures, and improve the function of the drill
string and tools in the hole. They are divided into two general types: water-
based fluids and oil-based fluids. The type of fluid base used depends on
drilling and formation needs, as well as the requirements for disposition of the
fluid after it is no longer needed. Drilling muds are a special class of drilling
fluids used to drill most deep wells. Mud refers to the thick consistency of the
formulation.
Following are the functions of a drilling mud:
1. To remove rock bit cuttings from the bottom of the hole and carry them
to the surface
2. To overcome the fluid pressure of the formation
3. To avoid damage of the producing formation
4. To cool and lubricate the drill string and the bit
5. To prevent drill pipe corrosion fatigue
6. To allow the acquisition of information about the formation being drilled
(., electric logs, cutting analysis)
Classification of Muds
The classification of drilling muds is based on their fluid phase alkalinity,
dispersion, and the type of chemicals used. We follow the classification of
Lyons [1135]; see Table 1-1.
Dispersed Noninhibited Systems
Drilling fluids used in the upper hole sections are referred to as dispersed
noninhibited systems. They are formulated from freshwater and may contain
bentonite. The classification of bentonite-based muds is shown in Table 1-2.
Table 1-1
Classification of Drilling Muds
Class Description
Freshwater muds—dispersed pH from 7-, include spud muds,
systems bentonite-containing muds,
phosphate-containing muds, organic
thinned muds (red muds, lignite muds,