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Pressure Required to Break Circulation

on . Posted in Drilling Engineering

Drilling pressure required to break circulation is the amount of pressure needed to re-establish or initiate fluid flow in a wellbore, particularly if the fluid column has become stagnant, if there's lost circulation, or after a prolonged period of no circulation.  Breaking circulation is often needed when drilling fluid has been static, causing potential pressure differences or blockages within the well.

Key Points about Determining the Pressure Needed to Break Circulation

Initial Circulating Pressure (ICP)  -  This is the pressure required to start the circulation in the well.  It is influenced by factors such as the depth of the well, fluid density, and formation pressures.  The ICP can be measured after circulation is established, but it’s often estimated based on prior circulating pressures.
Frictional Pressure Losses  -  This includes the pressure loss across the drillstring, annulus, and any flow restrictions.  This is usually estimated based on fluid properties, flow rate, and well geometry.
Hydrostatic Pressure  -  When breaking circulation, the static fluid column exerts a hydrostatic pressure on the formation.  Any additional pressure needed should overcome the hydrostatic pressure and any formation backpressure.

Practical Considerations

Mud Density  -  Heavier muds require more pressure to initiate circulation due to higher hydrostatic pressures.
Well Depth  -  Deeper wells require more pressure due to increased hydrostatic and frictional pressures.
Stuck Pipe or Obstructions  -  If there’s resistance or blockage in the well, additional pressure may be required to break through the obstruction.
Formation Pressure   -  In formations with high pore pressure, additional pressure may be required to initiate circulation.

  

Pressure Required to Break Circulation - Annular formula
\( P_{gs} \;=\;  [\; y  \;/\; 300 \; ( D_h - D_d ) \;] \; L  \)
Symbol English Metric
\( P_{gs} \) = Pressure to Overcome Mud's Gel Strength Inside Annulus (psi) \(lbf\;/\;ft^2\) -
\( y \) = Gel Strength of Drilling Fluid \(lbf\;/\;100\;ft^2\) -
\( L \) = Drillstring Length \(ft\) -
\( D_h \) = Diameter of Hole \(in\) -
\( D_p \) = Diameter of Drill Pipe \(in\) -

 

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Tags: Drilling Mud

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