STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

666 Drilling and Well Completions
Table 4-46
Yield of Drilling Clays [28]
Concentration
Mud Weight
Drilling Clay Yield, bbVton % Volume % by Weight lmbl Mud lbbbl
Highest quality 100 2.5 6 20 8.6
Common 50 6.0 13 50 9.1
Lowest quality 25 10.0 20 75 9.6
Native 10 23.0 40 180 11.2
Courtesy International Drilling Fluids
Table 4-47
Classification of Bentonite Fluid Systems [28]
Solid-Solid
Inhibition
Interactions Level Drilling Fluid Type
Dispersed Non-inhibited 1. Fresh water clay based fluids. Sodium
Dispersed
In hi bited
chloride less than 1 %, calcium ions less
than 120 pprn
a. Phosphate low pH (pH to 8.5)
b. Tannin-high pH (pH 8.5-11+)
c. Lignite
d. Chrome lignosulphonate (pH 8.5-10)
Saline (sodium chloride) fluids
a. Sea-water fluids
b. Salt fluids
c. Saturated salt fluids
Calcium treated fluids
a. Lime
b. Gypsum
Low concentration lignosulphonate fluids
Non-dispersed Non-inhibited Fresh water-low solids
a. Extended bentonite systems
b. Bentonite-polymer systems
Non-dispersed Inhibited Salt-Polymer fluids
Courtesy International Drilling Fluids
Dispersed Noninhibited Systems. Drilling fluid systems typically used to drill
the upper hole sections are described as dispersed noninhibited systems. They
would typically be formulated with freshwater and can often derive many of their
properties from dispersed drilled solids or bentonite. They would not normally
be weighted to above 12 lb/gal and the temperature limitation would be in the
range of 176-194°F. The flow properties are controlled by a deflocculant, or
thinner, and the fluid loss is controlled by the addition of bentonite and low
viscosity CMC derivatives.
Phosphate-Treated Muds
The phosphates are effective only in small concentrations. Phosphate treated
muds are subject to several limitations: