Drilling Fluids
WEL-BAR 4.1
™
Barium Sulfate
WEL-BAR 4.1 is predominantly barium sulfate (BaSO4, molar
mass 233.391 g/mol), the crystalline mineral barite which is
manufactured to API specification. It is insoluble in water and
is chemically inert to virtually all drilling-fluid additives. The
industry specifications for barite are given in API 13A 18th
edition, which is identical to ISO 13500:2009, and are set out
in the table below. WEL-BAR 4.1 specification is identical to
WEL-BAR in every respect except density.
ANSI/API Specification 13A 18th Edition February 2010
Barite Physical and Chemical Requirements
Requirement Standard ↓
Reference→
Table 2, Section 7, Barite
Table 19 Section 20, Barite 4.1
4.20 g/ml, minimum
4.10 g/ml, minimum
250 mg/kg, maximum
250 mg/kg, maximum
Mass fraction maximum 3.0%
Mass fraction maximum 3.0%
Density
Water-soluble alkaline earth
metals, such as calcium
Residue > 75 μm
Particles < 6 μm in equivalent
Mass fraction maximum 30% Mass fraction maximum 30%
spherical diameter
Pure barium sulfate has a density of 37.6 lb/gal (4.50 g/ml);
consequently, standard barite contains a number of impurities,
such as quartz, calcite, and celestite, which reduce the density
of typical ore to 35.1 lb/gal (4.20 g/ml). WEL-BAR 4.1 contains
a small incremental concentration of these impurities.
Applications
Advantages
• Insoluble and chemically inert except in very
specific brines
• Highly effective because of high density
• Economical because of abundance and ease
of mining and grinding
• Low abrasiveness
Typical Physical Properties
Appearance*
Powder
Specific gravity
4.10
Bulk density**
118 lb/ft3
1,900 kg/m3
Packaging
Sacks, big bags, and bulk
*Colors may vary from gray, buff, tan to pink
**Highly dependent on compaction
Usage
The quantities of WEL-BAR 4.1 required for density
increase are calculated as follows:
WEL-BAR 4.1, lb/bbl =
• WEL-BAR 4.1 is used to increase the density of all drilling
fluids. Fluid densities up to 2.40 SG (20 lb/gal) is achievable
in most drilling fluids while maintaining acceptable rheological
properties. Barite plugs and kill pills can be formulated up to
2.60 SG (22 lb/gal) for well-control operations.
• Fluid performance, e.g. plastic viscosity, yield point,
filtration control, etc., differs by slight margins in
comparison to 4.2 SG WEL-BAR product.
WEL-BAR 4.1, kg/m3 =
SG1 = initial density, g/cm3
SG2 = required density, g/cm3
1,437 (W2-W1)
34.2-W2
4,100 (SG2-SG1)
4.1 - SG2
W1 = initial weight, lb/gal
W2 = required weight, lb/gal
WEL-BAR 4.1 should not be used with concentrated
potassium and caesium formate brines, because
they act as chelating agents and produce hazardous
soluble barium.
Consult the MSDS, safety posters, and/or product
label before use, and use personal protective
equipment as advised.
Issued May 2011
weatherford.com
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