Blow Through Situation in Mud Gas Separator (Well Control Equipment)

Mud leg provides hydrostatic pressure in order to prevent mud going through the separator into the rig. If the pressure in the mud gas separator exceeds hydrostatic pressure provided by mud leg, gas blowing through situation will be happened. Once blow-through occurs with a mud gas separator, it is very difficult to stop this situation until the mud leg column is re-established.


Figure 1 illustrates mud-blow through. The pressure that will create blow-through can be calculated by determining hydrostatic pressure of mud leg.

Mud Leg and Blow Through 1

Figure 1 – Blow Through Situation


The equation below demonstrate the blow-through pressure.

Hydrostatic Pressure from Mud Leg = 0.052 × Mud Weight× Mud Leg


Hydrostatic Pressure from Mud Leg in psi

Mud Weight in ppg

Mud Leg in ft

Use the following data to calculate which pressure would blow-through occur.

Mud Leg = 20 ft

Mud Density in a mud gas separator = 13.0 ppg

Vent line length = 150 ft

Mud gas separator height = 25 ft


Only mud leg and mud density will be used in the calculation.

Mud Leg and Blow Through 2

Figure 2 – Mud Gas Separator Information

Hydrostatic Pressure from Mud Leg = 0.052 × 13.0 × 20

Hydrostatic Pressure from Mud Leg = 13.5 psi

It means that if it is required 13.5 psi in this mud gas separator to overcome the hydrostatic pressure and gas blow-through will be occurred.

Reference books: Well Control Books

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3 Responses to Blow Through Situation in Mud Gas Separator (Well Control Equipment)

  1. muhammad javed says:

    Mud gas separator height = 25 ft
    Not culcolate in.what reason behind this

  2. Hello ihop so to be perfect in the drilling feld culd you ples take me frind the page and send tome IWCF quitions

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