Kill Weight Mud or Kill Drilling Fluid Density is the mud weight required to balance formation pressure. The kill weight mud may be pumped into the well at different time depending on kill methods (Driller’s method, Wait and Weight, Bull head, etc).
How to determine kill weight mud?
With the following equation, you can determine this figure.
Kill Weight Mud (KWM) = Current Mud Weight + (SIDPP ÷ 0.052 ÷ Well TVD)
In water based mud, you can not only estimate the maximum surface casing pressure, but you are also be able to determine the maximum pit gain due to gas influx.
The following formula demonstrates how to figure out the maximum pit gain from gas influx in water based mud system.
Maximum Pit Gain in bbl
P is formation pressure in psi.
V is original pit gain in bbl.
C is annular capacity in bbl/ft.
Kill Weight Mud in ppg
Let’s take a look at this following example in order to get more understanding regarding this topic.
When a well is shut in due to well control operation, the casing pressure will increase due to gas migration and gas expansion. In water based mud, you are able to estimate the maximum surface pressure with this following formula.
Max surface pressure in psi.
P is expected formation pressure in psi.
V is pit volume gain in bbl.
KWM is kill weight mud in ppg.
An is an annular capacity in bbl/ft.
This is drilling formula calculation sheet v1 distributed on 28-Mar-10. I add many essential drilling formulas in to one Excel spread sheet and I would like to share with you for FREE. Please check this following link for download.
When you one the file Drilling-formulas-Calculation-shee-V1.xls, you will see the fist page call index page which shows you all of formulas like this.
You calculate the maximum initial shut-in casing pressure (MISICP) based on the original mud weight before you start drilling ahead. Once you drill deeper, you may increase mud weight. With new mud weight, you are not able to use the MASICP calculated by the initial weight because higher mud weight will reduce the MASCIP. The formula below demonstrates you how to adjust the MASICP with new mud weight.
Adjusted MASICP = Leak off pressure – [Shoe TVD x (MW2 – MW1)] x 0.052