Casing Shoe Pressure While Circulating Influx in Well Control Situation

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.

casing-shoe-presure

 First Scenario – Top of Gas Kick Below Casing Shoe

 

Figure 1 - Top of Gas Kick Below Casing Shoe

Figure 1 – Top of Gas Kick Below Casing Shoe

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Understand shoe pressure – Shoe pressure when the gas kick Passing Shoe

For this case, we will consider the shoe pressure when the gas kick is passing the casing shoe. See the image below.

Understand shoe pressure – Shoe pressure when the gas kick Passing Shoe

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

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Understand shoe pressure – Top of Gas Kick Below 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

Understand shoe pressure - Top of Gas Kick Below the 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.

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