API RP 13B-1:2026

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

a) drilling fluid density (mud weight);

b) viscosity and gel strength;

c) static filtration;

d) water, oil, and solids contents;

e) sand content;

f) methylene blue capacity;

g) pH;

h) alkalinity and lime content;

i) chloride content;

j) total hardness as calcium;

k) low-gravity solids and weighting material concentrations;

l) static filtration at high-temperature and high-pressure through permeability plugging testing.