Hello friends and STEM content lovers.
In this opportunity we continue in the same order of topics related to drilling fluids, this time with the reduction of drilling fluid density.
In the same way in which barite is used to increase the density of the drilling fluid, there is also another element with very different characteristics that serves for the opposite, that is, if barite is used to increase the density of the drilling fluid, water ends up being the necessary element to lower the density of the drilling fluid.
When we add water to the drilling fluid we are diluting the mixture, therefore the density goes down, but what is really important is to ask ourselves the following question:
Under what drilling operating conditions is it desirable to reduce the drilling fluid density?
When drilling with a drilling fluid that performs the function of lifting the formation cuttings that are cut with the drill bit, there is a risk that much of these cuttings cannot be filtered by the solid control equipment and become mixed with the drilling fluid, causing the incorporation of these solids into the drilling fluid to increase its density above the preset values.
When this happens, either because the drilling fluid personnel have measured the density and realized that it is above the values required by the drilling program, then they must proceed to dilute the drilling fluid (add water) to lower the density of the drilling fluid. The amount of water that will be needed to lower the density of the drilling fluid is calculated using the following equation:
An example would be: Determine the volume of water required to decrease the drilling fluid density from 15 lbs/gallon to 12 lbs/gallon considering an initial drilling fluid volume of 90 barrels.
Applying the equation and substituting the data in the equation we are left with:
In order to lower the density of a water-based drilling fluid from 15 lbs/gallon to 12 lbs/gallon and with an existing volume of 90 barrels of fluid, it is necessary to add approximately 74 barrels of water.
The important thing about this calculation is that it estimates the precise volume of water that we must add to dilute the drilling fluid and thus be able to lower the density of the drilling fluid without having miscalculations that suddenly allow us to lower the density too much or not enough.
Recommended references
Additional barite sacks due to increase in drilling mud density | Petroleum Engineering