STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

Drilling Muds and Completion Fluids 663
A standard procedure for estimating the salt content of oil-base muds consists
of the following steps [26]:
1. Determination of calcium chloride concentration, lb/bbl.
2. Determination of sodium chloride concentration, lb/bbl.
3. Determination of soluble sodium chloride. By entering the graph in
Figure 4-109 with the lb/bbl of calcium chloride at the correct volume
percent of water (by retort) line, the maximum amount of soluble sodium
chloride can be found. If the sodium chloride content determined in Step 2
is greater than the maximum soluble sodium chloride determined from
Figure 4-108, only the soluble portion should be used for calculating the
total soluble salts.
4. Determination of total mud salinity. The total pounds of soluble salts per
barrel of mud are calculated as
Total soluble salts (lb/bbl) = CaCl, (lb/bbl) - soluble NaCl (lb/bbl)
5. Determination of water phase salinity. By entering the graph in Figure 4-1 10
with total soluble salts, lb/bbl of mud, at the correct volume percent of
water line, the water phase salinity can be read from the left-hand scale.
Example. Find the total salinity of the oil-base mud using the test data below
and Figures 4-108 and 4-109.
Volume % water = 12%
From Ca titration, the CaCI, concentration is 18 lb/bbl mud
From C1 titration, the NaCl concentration is 9.9 Ib/bbl mud
Step 1. The maximum soluble NaCl (from Figure 4-109) = 3 lb/bbl. (There is
excess insoluble NaCl = 6.9 Ib/bbl.)
Step 2. The total soluble salts in the mud = 18 + 3 = 21 lb/bbl.
Step 3. The water phase salinity (from Figure 4-110) = 330,000 ppm.
Water Wetting Solids. The water wetting solids test (oil-base mud coating test)
indicates the severity of water wetting solids in oil-base mud [24]. The items
needed are
1. Hamilton Beach mixer
2. Diesel oil
3. Xylene-isopropyl alcohol mixture
4. 16-02. glass jar
Collect a 350-ml mud sample from the flowline and place the sample in the glass
jar. Allow the sample to cool to room temperature before the test is conducted.
Mix at 70 V with the mixer for 1 hr. Pour the mud out, add 100 ml diesel oil, and
shake well. (Do not stir with mixer.) Pour the oil out, add 50 ml xylene-isopropyl
alcohol (1:l) mixture, and shake well. Empty jar, turn upside down, and allow to
dry. Observe the film on the wall of the jar and report the evaluation as
Opaque film-severe problem, probably settling of barite and plugging of the
drill string.
Slight film, translucent-moderate problem, mud needs wetting agent immediately.
Very light film, highly translucent-slight wetting problem, mud needs some
treatment.
No film-no water wetting problem.