Pressure Required to Break Circulation in Drillstring Formula |
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| \( P_{gs} \;=\; y \cdot \dfrac{ L }{ 300 \cdot d _p } \) | ||
| Symbol | English | Metric |
| \( P_{gs} \) = Pressure to Overcome Mud's Gel Strength Inside Drillstring (psi) | \(lbf\;/\;ft^2\) | - |
| \( y \) = Gel Strength of Drilling Fluid | \(lbf\;/\;100\;ft^2\) | - |
| \( L \) = Drillstring Length | \(ft\) | - |
| \( d_p \) = Drill Pipe ID | \(in\) | - |
The pressure required to break circulation in a drillstring is the pressure needed at the surface to initiate mud flow after a period of inactivity where the drilling fluid has gelled and potentially allowed cuttings to settle. This pressure must overcome the gel strength of the drilling mud and any static friction of settled solids. It depends on the mud's gel strength, the internal diameter, and the length of the drillstring.
Pressure to overcome gel strength in the annulus is the pressure is needed to break the gel strength of the mud in the annular space between the drillstring and the wellbore or casing. It depends on the mud's gel strength, the length of the drillstring, and the annular diameter.
The pressure to overcome static friction of settled solids when drilling has been stopped for an extended period, cuttings and other solids in the mud can settle, creating a resistance to flow. This component is harder to quantify precisely and depends on factors like the type and concentration of solids, the settling time, and the wellbore geometry (inclination, doglegs). In practice, this is often accounted for by gradually increasing pump pressure.
