STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Drilling Muds and Completion Fluids 689
% oil in liquid phase = - 51 x100= 75%
51 + 17
% water in liquid phase = - l7 x100=25%
17 + 51
Change of OilMlater Ratio
It may become necessary to change the oil/water ratio of an oil mud while
drilling. If the oil/water ratio is to be increased add oil, if it is to be decreased,
add water. To determine how much oil or water is to be added to change the
oil/water ratio, the following calculations are made:
1. Determine present oil/water ratio.
2. Decide whether oil or water is to be added.
3. Calculate how much oil or water is to be added for each hundred barrels
of mud as follows:
Example A. Retort analysis:
51% oil by volume
17% water by volume
32% solids by volume
O/W ratio is 75/25 (from previous example). Change oil/water ratio to 80/20. Use
basis of 100 bbl of mud.
Table 4-54
Comparison of Diesel Oil and Mineral Oil Muds [33]
Diesel-Oil
Mineral Oil
Formulation or Property Mud Mud
Oil, bbl 0.59 0.59
Primary Emulsifier, Ib 9 9
Secondary Emulsifier, Ib 2 2
Lime, Ib 5 5
High-Temperature Stabilizer, Ib 8 8
Water, bbl 0.2 0.2
Organophilic Bentonite, Ib 3 3
Barite, Ib 214 214
Calcium Chloride, Ib 37.2 37.2
Aged at 3OO0F, hour - 16 - 16
Plastic Viscosity, cp 55 39 47 32
Yield Point, lb/100 sq. ft. 30 26 27 20
10-Min. Gel, lb/lOO sq. ft. 14 14 13 13
Electrical Stability, volts 960 1030 880 930
API Filtrate, ml 0.6 1.6 1.4 2.0
300°F Filtrate, ml 6.6 6.8 8.4 12.4
Courtesy SPE.