THE EFFECT OF SOME MATERIALS ON FUNNEL VISCOSITY READING IN WATER BASE MUD
Since Marsh funnel is the most famous and quick tool that used in field operations. When a crew get sample from the well and test it to show the effect of some materials on mud viscosity, it should take into consideration that there are many materials affect on the funnel viscosity like weighting materials, thinners, and polymers. Weightings material additives are essential to give adequate hydrostatic pressure to confirm borehole stability. Barium sulphate is the predominant weighting material. Many mud samples were prepared which involved freshwater, caustic soda, Bentonite, and weighting material. The weighting materials are added to mud distinctly alone to form the requisite mud density varieties between 8.7 ppg to 10 ppg. Likewise, a slight variance was detected in plastic and apparent viscosities. The experiments are done for another two substances like carboxy methyle cellulose and Lignite to show their effect on the funnel viscosity. Adding carboxy methyle cellulose led to increase the funnel viscosity, but adding Lignite led to reduce funnel viscosity. The results show that not only the viscosity affect on the funnel viscosity reading but also the density of drilling fluid have an effect on the funnel viscosity reading. The results show that when the solild percentage low about 1% or 2%, all the tested materials gave the same value of the funnel viscosity about (40–42) sec, that mean at low soild percentage we cannot know which material behind that change, so we should take that point into our consideration. Thus, it is concluded that mud density is another factor that affects funnel viscosity, and this point should be taken in consideration especially in-field testing and operations to avoid wrong interpretation for the tested field samples.