DRILLING MUD CALCULATION
Mud weight calculation The mud weight or mud density is determine by the volumes and types of solids added to the mud system. The following equations can be used to calculate the mud weight.
Equation - 1
Equation - 2
Command mud additive TABLE -1
Density control computation The final mud volume after changing the mud from density (1) to density (2) is computed with : Equation - 3
In practice, since excess storage capacity is not available and to limit the amount of added, costly weighting material, before the density increase (by adding barite), some mud volume is discarded from the circulation system. In this situation, the volume the existing mud has to be reduced to before weighting material added:
Equation - 4
Density control computation With knowledge of the volumes, the densities of the original mud and the weighting material, the weight of barite required is given by:
Where :
Density control computation Due to the barite’s extremely large surface area, barite has tendency to adsorb a large amount of water from the mud system and thus increases the viscosity of drilling mud. This thickening is avoided when not only barite but also a minimum amount of water, to wet the barite, is added simultaneously. A common practice is to add 1 [gal] of water for each added 100 [lbm] of barite. To take this extra water into account and when assuming that original mud is discarded before weighting, following equation give the volume of original mud and the amount of barite required:
Density control computation
Density control computation When the concentration of low-gravity solids should be kept to a minimum value, it is cheaper to educe them by dilution before weighting the original mud with barite. The following equations are applied to calculate the corrected volume of the original mud, V1, the volume of the dilution water, Vw, the mass of weighting material, m2, and the obtained final mud volume V2 after weighting:
EXERCISE 1. When 180 [lbm] of API barite, 60 [lbm] of bentonite and 2 [bbl] of water are mixed, what is the resulting density? Answer: Used equation [1] and [2], Refer Table-1 to measured density.
EXERCISE 2. When 90 [lbm] calcium chloride is mixed with 3 [bbl] of water, what is resulting density? Answer : Used equation [1] and [2], Refer Table-1 to measured density.
EXERCISE 3. 700 [bbl] of mud have to be increased in density from 13 [ppg] to 15 [ppg] by adding API barite. Since the mud thickness has to be maintained, 1 [gal] of water is added with every 100 [lb] of barite. Calculate the total amount of water and barite required. Answer:
EXERCISE 4. When 1,000 [bbl] of mud have to be increased from 10 [ppg] to 13 [ppg] mud weight by adding API Barite, the total voume is limited to 1,000 [bbl]. How much an old mud has to be discarded and what is the weight of the added API barite?
Answer:
