Drilling fluid or drilling mud as many people call it is a vital element of the rotary drilling process. The term Drilling Fluid includes air, gas, water and mud. Mud refers to the liquid that contains solids in water or oil. The mud is made up with clay and other additives but get a desirable properties.
Water Based Mud
Often, water is the base of drilling mud. Water makes up the liquid part or phase have a water-based mud. Crew members put clay in special additives into the water to make a mud with the properties needed to do its job well. For example, clays gives a thickness for viscosity but water in the mud maybe freshwater, seawater or concentrated brine. Saltwater, the one used depends on its availability and whether it gives the mud the needed properties to drill the hole efficiently.
At times, down-hole drilling conditions require the crew to add oil to the mud or in some cases crew members used oil instead of water as the base have them. This is called Oil-based mud. Oil-based mud has many advantages, it can stabilize the formation and reduced down-hole drilling problems. However it is harder for the crew to work with because it can create slippery conditions and environmental precautions must be used. From an environmental standpoint, mud with oil is more difficult to handle because the oil clings to the drill cuttings. The oil must be cleaned of the cuttings before they are disposed of.
Drilling With Air
Sometimes drilling fluid is dry air or natural gas, here dry air is coming out of the rigs Blooey Line carrying very fine drill cuttings. Air drilling uses large air compressors instead of mud pums. Drilling with air of gas can prevent formation damage and overcome severe lost circulation problems. And it allows the bit to drill very fast. Down-hole conditions have to be just right for air or gas to be usable. For example, the bit cannot drill through formations containing large amounts of water, the water mixes with the cuttings in the air or gas and clogs up the hole.
Used small amounts of water are present in the formations being drilled. Special equipment can inject a forming agent into the air stream. The foam help separate the cuttings and remove water from the hole.
In some case the rig operator may use Aerated mud which like foam drilling helps prevent clogging up the well bore. Aerated drilling uses both air and mud pimped into the standpipe at the same time.