Many people ask us a lot of questions regarding shoe pressure while circulating kick (wellbore influx) out of the wellbore. Pressure acting at casing shoe is different depending on where the kick is in the well therefore we will summarize all the scenarios to help you get clearer picture. There are a total of three cases which we will separately discuss as per the details below.
Note: All the calculations and scenarios are based on water based mud and gas kick. This assumption is used because it is the worst case scenario. The casing shoe will have less pressure if the influx is oil or gas kick.
First Scenario – Top of Gas Kick Below Casing Shoe
Figure 1 – Top of Gas Kick Below Casing Shoe
We have learned 2 cases about shoe pressure when kick is underneath shoe, and kick is passing the shoe,
When gas kick is being move above the shoe, do you know how much pressure at shoe has?
I will explain this case via this blog post.
For this case, we will consider the shoe pressure when the gas kick is passing the casing shoe. See the image below.
Let’s apply the hydrostatic pressure concept.
The formula for the bottom hole pressure is listed below:
Bottom Hole Pressure = Pressure at casing shoe + Hydrostatic Pressure in the open hole underneath the shoe
I would like to address about the shoe pressure concept while while circulating gas influx out of wellbore. This is the fist scenario – Top of the gas kick below the casing shoe
The hydrostatic pressure above the casing shoe remained constantly because the fluid column is the same. The over all hydrostatic pressure in the well will decrease because gas expansion when it is being circulated. In order to maintain the bottom hole pressure constant, casing pressure will increase to balance the loss of hydrostatic pressure in the wellbore due to expansion.