BAKER HUGHES - Drilling Fluids Reference Manual

Baker Hughes Drilling Fluids
Low-Gravity Solids Analysis
As previously stated, the differences in cation exchange capacities of commercial bentonite and
drilled solids allows the use of the methylene blue test to distinguish between them. From the earlier
equations, we can deduce that,
or
where,
Error! Objects cannot be created from editing field codes.
Methylene BlueCapacity =
+
mL of methyleneblue
g of drilled solids
mL of methyleneblue
g of bentonite
( ρ )
⎛ vol % drilled solids ⎞
( ρ ) ⎜
⎟
⎠
drilled solids
ρ bent = density of bentonite, g/cm 3
ρ drilled solids = density of drilled solids, g/cm 3
⎝
100
The following rewrites the equation in terms of cation exchange capacities,
Methylene blue
capacity
bent
vol % Bentonite
= ( CEC bent )( ρ bent ) ⎛------------------------------------------
⎞
⎝ 100 ⎠
vol % drilled solids
+ ( C EC DS )( ρ DS ) ⎛---------------------------------------------------
⎞
⎝ 100 ⎠
The equation can be rewritten as,
M ethylene blue
capacity
vol % LGS
= ( CEC avg )( ρ LGS ) ⎛----------------------------
⎞
⎝ 100 ⎠
Then, equating the two equations above, you have,
⎛ vol % bentonite
⎜
⎝ 100
vol % LGS
( CE C avg )ρ ( LGS ) ⎛----------------------------
⎞ vol % Bentonite
= ( CEC
⎝ 100 ⎠ bent )( ρ bent ) ⎛------------------------------------------
⎞
⎝ 100 ⎠
vol % drilled solids
+ ( CEC DS )( ρ DS )
⎛----------------------------------------------------⎞
⎝ 100 ⎠
We have previously defined low-gravity solids as comprised of commercial bentonite and
incorporated drilled solids, or,
which can be written,
% LGS = % Bentonite + % DS
% DS = % LGS – % Bentonite
Making further equation substitutions, you see that,
( CEC avg )ρ ( LGS ) ⎛ % ------------------
LGS ⎞ % Bentonite
= ( CEC
⎝ 100 ⎠ bent )( ρ bent ) ⎛---------------------------------
⎞
⎝ 100 ⎠
⎞
⎟
⎠
Baker Hughes Drilling Fluids
Reference Manual
Revised 2006 1-29