**1. n. []**

The pressure, usually measured in pounds per square inch (psi), at the bottom of the hole. This pressure may be calculated in a static, fluid-filled wellbore with the equation:

BHP = MW * Depth * 0.052

where

- BHP is the bottomhole pressure in pounds per square inch
- MW is the mud weight in pounds per gallon
- depth is the true vertical depth in feet
- 0.052 is a conversion factor if these units of measure are used.

For circulating wellbores, the BHP increases by the amount of fluid friction in the annulus. The BHP gradient should exceed the formation pressure gradient to avoid an influx of formation fluid into the wellbore.

On the other hand, if BHP (including the added fluid friction pressure of a flowing fluid) is too high, a weak formation may fracture and cause a loss of wellbore fluids. The loss of fluid to one formation may be followed by the influx of fluid from another formation.

**Alternate Form:**
BHP

**See related terms:**
formation pressure

**2. n. []**

The pressure measured in a well at or near the depth of the producing formation. For well-test purposes, it is often desirable to refer the pressure to a datum level chosen at a reference depth by calculating the pressure that would occur if the pressure measurement were made at the datum level rather than at the actual depth of the gauge.

**Alternate Form:**
BHP

**See related terms:**
depth reference

**3. n. []**

The downhole pressure, measured or calculated at a point of interest, generally the top of the perforated interval.

**Alternate Form:**
BHP