The osmotic pressure is  a pressure that must be  applied to a more concentrated solution to bring about equilibrium between the solvent in two solutions of different concentrations that are separated by a semipermeable membrane.

A drilling mud is typically a suspension of solids and possibly also liquids or gasses in a liquid. The suspended solid particles or fluid globules from the discontinuous phase of the mud.

The function fluid must perform; the fluid properties that help to achieve these functions, and possible undesirable side effects that should be minimized. Unfortunately, fluid properties that are useful for the performance of one function may be determinate to another.

Before going into detail of drilling fluid technology it is interesting to know the sequence of events which lead gradually to the various developments and ultimately resulted in the present stage when success of drilling a hole is attributed to be significantly depends on the better performance of a circulating fluid.

The term mud originate from clay (native / commercial) suspension in water which were used initially to circulate out cutting from the hole during drilling operation and this term is still used widely in the drilling technology.

The forces that exist within a fluid at any point may arise from various sources. These include gravity, or the ‘‘weight’’ of the fluid, an external driving force such as a pump or compressor, and the internal resistance to relative motion...

It is basically a physical science, based on the observations of physical phenomena followed by the experimental evidence which verify that it is correct. Finally, once the principles have been accepted then these observations are translated into mathematical

Based on the molecular theory, temperature has been defined as follows."Temperature indicates the speed of motion of the molecules" or "Temperature measures the speed of motion of one molecule".