The slight increase in mud weight needed to offset the loss in hydrostatic pressure when the riser is disconnected from the SS BOPE and the hydrostatic pressure of the mud from RKB to the mud line is replaced by the hydrostatic pressure of weight of the column of sea water from sea level to the mud line.

Related Terms

• Equivalent Circulating Density (ECD)

the increase in bottomhole pressure expressed as an increase in pressure that occurs only when mud is being circulated. Because of friction in the annulus as the mud is pumped, bottomhole pressure is slightly, but significantly, higher than when the mud is not being pumped. ECD is calculated by dividing the annular pressure loss by...

• Circulation Loss

The loss of drilling fluid to a formation, usually caused when the hydrostatic head pressure of the column of drilling fluid exceeds the formation pressure. This loss of fluid may be loosely classified as seepage losses, partial losses or catastrophic losses, each of which is handled differently depending on the risk to the rig and personnel and...

• Hydraulic Head

the force exerted by a column of liquid expressed by the height of the liquid above the point at which the pressure is measured. Although “head” refers to distance or height, it is used to express pressure, since the force of the liquid column is directly proportional to its height. Also called head or hydrostatic...

• Pressure Surge

a sudden, usually short-duration, increase in pressure. When pipe or casing is run into a hole too rapidly, an increase in the hydrostatic pressure results, which may be great enough to create lost circulation...

• Trip Margin

the small amount of additional mud weight carried over that needed to balance formation pressure to overcome the pressure-reduction effects caused by swabbing when a trip out of the hole is made....