Drilling mud composition

Drilling mud, also known as drilling fluid, is a product which is used in the process of drilling deep boreholes. These holes may be drilled for oil and gas extraction, core sampling, and a wide variety of other reasons. The mud can be an integral part of the drilling process, serving a number of functions.

One of the most critical roles of drilling mud is as a lubricant. Drilling generates tremendous friction, which can damage the drill or the formation being drilled. Drilling mud cuts down on the friction, lowering the heat of drilling and reducing the risk of friction-related complications. The mud also acts as a carrier for the materials being drilled, with material becoming suspended in the mud and then being carried up the drill to the surface.

Using drilling mud protects the stability of a borehole by controlling variables such as friction and pressure. Different muds are needed for different circumstances, and the selection and formulation of mud is managed by a mud engineer. This engineer determines the correct viscosity level for the drilling mud, and adjusts factors such as density of the mud as well. Water, oil, and gas-based muds can all be used, with products ranging from true muds made with materials like bentonite clays to synthetic drilling fluid.

Drilling mud is recirculated throughout the drilling process. As it rises to the surface, it passes through screens which trap the materials from the borehole, before being cycled back into the system which delivers mud to the head of the drill bit. This recirculation process is designed to cut down on waste by reusing as much mud as possible. Depending on the materials being drilled, several screens may be needed to trap the materials, and sometimes the materials themselves are also coated in mud, which means that they will need to be cleaned even after filtration.

drilling fluid functions  
-cuttings removal
-suspension of cuttings
-release of cuttings at surface
-transmission of hydraulic power to the drilling bit 
-minimising formation damage
-reducting filtration rate
-cooling and the lubrication of the drill bit and drill string
-buoyancy support of the drill string
-corrosion prevention
-data logging

Table1 

Composition of a typical bentonite gel water based mud ,density 1300kg/m3.   Components added to 1 barrel of water : (bbl=barrel, pps=pounds per barrel); CMC :(carboxymethylcellulose)

component	quantity	Mass(kg)	Volume(L)	%mass	%volume
Water	1 bbl	159	1588,99	65,33	84,92
Bentonite	20 ppb	9,1	9,07	3,73	4,85
Caustic soda	0,5 ppb	0,23	0,22	0,9	0,12
Soda ash	0,5 ppb	0,23	0,10	0,9	0,5
High viscosity cmc	1,5 ppb	0,68	0,47	0,28	0,25
Low viscosity cmc	3,5 ppb	1,59	1,09	0,65	0,58
barite	160 ppb	72,58	17,28	29,82	9,23

 Table 2

Composition of a typical oil based mud density 1318 kg/m3 , salinity 22.5%,  oil to water ratio 65:35. components combine to give a total volume of one barrel.(bbl: barrel; ppb:pounds per barrel; gpb: gallons per barrel) 

	quantity	Mass(kg)	volume(L)	%mass	%volume
Base fluid	0,5 bbl	64,63	83,31	30,37	52,40
viscosifier	5 ppb	2,26	1,40	1,08	0,88
Emulsifier 1	0,8 ppb	2,89	3,02	1,38	1,90
Emulsifier 2	0,4 ppb	1,49	1,51	0,71	0,95
Lime	5 ppb	2,26	1,00	1,08	0,63
water	0,30 ppb	47,15	47,22	22,50	29,70
Clca2	30,2 ppb	13,70	3,35	6,54	2,11
barite	167,9 ppb	76,15	18,16	36,34	11,42