Page 209 - Formulas and Calculations for Petroleum Engineering

202 Formulas and calculations for petroleum engineering

3.59 Well flow efficiency (geothermal well)

Input(s)
*
p : Horner’s False Pressure at (t + Dt ¼1) (psi)
P wf : Bottomhole Pressure at a flowing well (psi)
Dp skin : Pressure Drop caused by the Skin Effect (psi)

Output(s)
FE: Flow Efficiency (per cent)

Formula(s)

p p Dp
wf skin
FE ¼

p p
wf
Reference: Ramey Jr, H. J. (1981). Reservoir Engineering Assessment of Geothermal Systems. Department of Petroleum
Engineering, Stanford University, Page: (5.14).
3.60 Well shut-in pressure during buildup (Horner plot)

Input(s)

p i : Initial False Pressure (psi)
Q o : Stabilized Well Flow Rate before Shut-in (STB/day)
B o : Oil Formation Volume Factor (bbl/STB)
k: Permeability (mD)
m o : Oil Viscosity (cP)
t p : Flowing Time before Shut-in (h)
Dt: Shut-in Time (h)
h: Thickness (ft)

Output(s)

p ws : Shut-in Pressure (psi)

Formula(s)

162:6 Q m B o t + Dt

p
o
o
p ¼ p log
ws i
k h Dt
Reference: Ahmed, T., McKinney, P.D. 2005. Advanced Reservoir Engineering, Gulf Publishing of Elsevier, Chapter: 1,
Page: 56.