To find c:


Petroleum Engineering Equations & Formulas

Compressibility of oil

Pressure depletion in the reservoir can normally be assumed to be isothermal, such that the isothermal compressibility is defined as the fractional change in volume per unit change in pressure:

       c = -(1/V) DOT dV/dP  [psi-1] or [bar-1]


       dV : derivative of volume
       dP : derivative of pressure
       V  : volume

$$ c = -\frac{1}{V} * \frac{dV}{dP}\; \;[psi^{-1}] \;or\; [bar^{-1}] $$


  • dV is the volume derivative
  • dP is the pressure derivative
  • V is the volume