API RP 13B-2

Please note that any addenda or errata may not be included in translated editions of this standard.

This recommended practice provides standard procedures for determining the following characteristics of oil-based drilling fluids:

a) drilling fluid density (mud weight);
b) viscosity and gel strength;
c) filtration;
d) oil, water, and solids concentrations;
e) alkalinity, chloride concentration, and calcium concentration;
f) electrical stability;
g) lime and calcium concentrations, calcium chloride, and sodium chloride concentrations;
h) low-gravity solids and weighting material concentrations.


The annexes provide additional test methods or examples that can optionally be used for the determination of:

• shear strength (Annex A);
• oil and water concentrations from cuttings (Annex B);
• drilling fluid activity (Annex C);
• aniline point (Annex D);
• lime, salinity, and solids concentration (Annex E);
• sampling, inspection and rejection (Annex F);
• rig-site sampling (Annex G);
• cuttings activity (Annex H);
• active sulfide (Annex I);
• calibration and verification of glassware, thermometers, viscometers, retort kit cups, and drilling fluid balances (Annex J);
• high-temperature/high-pressure filtration using the permeability-plugging apparatus (PPA) (Annex K);
• elastomer compatibility (Annex L);
• sand content of oil-based fluid (Annex M);
• identification and monitoring of weight-material sag (Annex N);
• oil-based drilling fluid test report form (Annex O).