## Hydrostatic Pressure

As mentioned earlier, this is the pressure created by a column of fluid due to its density and vertical height. This type of pressure always exists and may be calculated whether the fluid is static or flowing. It can be calculated using:

Hp(psi) = MWx 0.0519 x TVD( ft) Hydraulic Pressure

This is the pressure created (or needed) to move drilling fluid through pipe. In oil field terms, it is the pressure generated by the mud pump in order to move the drilling fluid from the mud pump around the system and back to the flowline. In this section, the terms Pump Pressure and Hydraulic Pressure will be used interchangeably. This type of pressure can be calculated at any point in the circulating system.

Pressure drop or pressure loss is the amount of pressure needed to move the fluid over a given distance, for example, the hydraulic pressure (pump pressure) remaining at point B in the figure is 600 psi. However, the system pressure loss at point B is 300 psi. That is, 300 psi is needed to pump the mud from point A to point B.

The hydraulic pressure (pump pressure) remaining at point E in the figure is 225 psi. However, the system pressure loss at point E is 675 psi. That is, 675 psi is required to move the mud from point A to point E. (300 psi from A to B and 375 psi from B to E.)

Exercise 1-4: How much hydraulic pressure is being exerted at points C and D?

Point C

Point D

Exercise 1-5: What is the pressure drop (loss) between the following points?

psi psi

psi psi

The total system pressure loss in the drawing (A to F) is 900 psi.

The total system pressure loss in the drawing (A to F) is 900 psi. Note: The pressure at any given point in the circulating system is the sum of the hydrostatic, hydraulic, and imposed pressures which exist at that point.

### Typically, hydraulic pressures will be calculated in order to:

• Determine the total pressure being exerted at the casing shoe (generally the weakest point in the circulating system); the bottom of the hole; or any other point (such as a lost circulation zone). After this pressure is determined, it is often converted into a mud density equivalent and reported as the E.C.D. (Equivalent Circulating Density) for that depth.
• Determine the anticipated pump pressure, using:
• mud properties
• drill string configuration
• bit size
• total flow area for the bit
• flow rate
• Determine the nozzle size for a bit, using:
• maximum pump pressure allowed
• mud properties
• drill string configuration
• bit size
• flow rate

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### Responses

• LANDOLFO
How to explain total flow area?
8 years ago
• camelia
What is hydrostatic pressure in oilfield terms?
8 years ago
• pandora
How much pump pressure is needed to overcome downhole hydrostatic pressure?
6 years ago
• katri hasu
What is hydraulic pressure in drilling?
5 years ago