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Mobility Calculation

Darcy's law states that the flow rate of a fluid through a porous medium is proportional to the pressure gradient across the medium. A Darcy is defined as a flow rate of 1 cc/s through a 1 cm2 cross-sectional area when subjected to a pressure difference of 1 atmosphere across 1 cm of material. The equation relates flow rate, permeability of the material, viscosity of the fluid, and the pressure difference across the material. Mobility is a measure of how easily a fluid can flow through a porous medium and is calculated by dividing permeability by viscosity. Mobility pre-tests may indicate either mud filtrate or formation fluid viscosity depending on factors like fluid composition and probe size.

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Ardian Aby Santosa
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545 views7 pages

Mobility Calculation

Darcy's law states that the flow rate of a fluid through a porous medium is proportional to the pressure gradient across the medium. A Darcy is defined as a flow rate of 1 cc/s through a 1 cm2 cross-sectional area when subjected to a pressure difference of 1 atmosphere across 1 cm of material. The equation relates flow rate, permeability of the material, viscosity of the fluid, and the pressure difference across the material. Mobility is a measure of how easily a fluid can flow through a porous medium and is calculated by dividing permeability by viscosity. Mobility pre-tests may indicate either mud filtrate or formation fluid viscosity depending on factors like fluid composition and probe size.

Uploaded by

Ardian Aby Santosa
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as XLS, PDF, TXT or read online on Scribd
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Definition

Darcy’s Law:
flow rate is proportional to pressure difference

What is a ‘ Darcy’ ?
a pressure difference of 1 atm * over 1 cm
gives a flow rate of 1 cc/s through a 1 cm2 area

Equation
flow rate permeability pressure differe
= x
area viscosity

Qx / A = (k /  ) x (  P/  x )

*1

Mobility value is depend on the viscosity of the format


Pretest (maximum 20cc) Mobility : Mud Filtrate is the biggest
After Pumping (several Liters) Mobility: Formation Fluid is the big
permeability In Oil Base Mud system: Mud filtrate = OIL
GAS Zone: Pretest Mobility normally less than After Pumping Mo
Mobility = because GAS has less viscosity than MUD FILTRAT
viscosity OIL Zone: Pretest Mobility can be less, equal or bigger than Aft
depend on OIL viscosity
WATER Zone: Pretest Mobility normally bigger than After Pumpi
because WATER has bigger viscosity than MUD FIL
pressure difference

tm * over 1 cm
hrough a 1 cm2 area

pressure difference
distance

*1 atm ~ .1 Mpa = 14.7 psi

n the viscosity of the formation fluid or mud filtrate


y : Mud Filtrate is the biggest contributor to viscosity
Mobility: Formation Fluid is the biggest contributor to viscosity
d filtrate = OIL
mally less than After Pumping Mobility,
less viscosity than MUD FILTRATE
n be less, equal or bigger than After Pumping Mobility,
cosity
normally bigger than After Pumping Mobility,
as bigger viscosity than MUD FILTRATE
Drawdown Mobility Calculation for MDT

Standard Diameter Probe 5660.0


Large Diameter Probe 2395.0
Extra Large Diameter Probe 1556.5
E-Probe (Cardinal) 1191.4
E-Probe (Astro) 840.4
E-Probe (Falcon) 856.4

Probe Types Standard Diameter Probe


Draw down proporsionally factor 5660
Draw down Pressure (psia) 1000
Last Buildup Pressure (psia) 2000
Pretest Rate (cc/min) 120

Drawdown Mobility (mD/cp) 11.3


n for MDT

Input the probe type used for pretest


(automatically) Drawdown Proportionally Factor
Input minimum drawdown pressure during pretest
Input Last Buildup Pressure/Formation Pressure
Input Pretest Rate used for pretest
Probe Types Large Diameter Probe
Draw down proporsionally factor 2395
Draw down Pressure (psia) 3320
Last Buildup Pressure (psia) 3430
Pretest Rate (cc/min) 120

Drawdown Mobility (mD/cp) 43.5

Very Good Match

3430 psia

3320 psia

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