Surface Pressure During Drill Stem Tests

Determine formation pressure:

psi = formation pressure equivalent mud wt, ppg x 0.052 x TVD, ft

Determine oil hydrostatic pressure:

psi = oil specific gravity x 0.052 x TVD, ft

Determine surface pressure:

Surface pressure, psi = formation pressure, psi — oil hydrostatic pressure, psi

Example: Oil bearing sand at 12,500 ft with a formation pressure equivalent to 13.5 ppg.

If the specific gravity of the oil is 0.5, what will be the static surface pressure during a drill stem test?

Determine formation pressure, psi:

FP, psi = 13.5 ppg x 0.052 x 12,500 ft FP = 8775 psi

Determine oil hydrostatic pressure:

Determine surface pressure:

Surface pressure, psi = 8775 psi — 2707 psi Surface pressure = 6068 psi

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  • linda goodbody
    How to calculate pressure for drill stem test?
    9 years ago

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