Definition - What does Non-Dispersed Mud mean?
Non-dispersed mud is used to simulate the characteristics of clear water where clear water cannot be used for drilling for various reasons.
The composition of the mud is water, bentonite, and polymers which are added to increase viscosity through flocculation or by viscosifying the water phase. Non-dispersed drilling fluids contain less than 5% low-gravity solids and are also sometimes called low-solids non-dispersed (LSND) mud. It does not perform well with reactive shales and is best suited to hard formations where the penetration rate is very slow.
Non-dispersed mud is also known as non-dispersed drilling fluid or non-dispersed polymer mud.
Trenchlesspedia explains Non-Dispersed Mud
The most commonly used non-dispersed muds are BEN-EX muds, low-solids PAC/CMC muds, and low-solids PHPA muds.
Non-dispersed muds are less tolerant of solids and contamination because they do not contain a dispersant. They also do not require an elevated pH. BEN-EX is used to increase the yield of bentonite and to flocculate drilled solids, but its use is limited to water containing less than 5000 mg/l of chlorides. It acts as a flocculant for non-bentonitic clays. Low-gravity solids are kept below 5% by volume, with the best performance at 2 to 3% volume range.
Fluid-loss control and viscosity are maintained via polymers in non-dispersed muds but these muds are highly susceptible to contamination from the formation, from produced gasses and from fluids.