2019 EJRNL PP MOHAMED MAHMOUD 1.pdf)u
Terbatas  Suharsiyah
» Gedung UPT Perpustakaan
Terbatas  Suharsiyah
» Gedung UPT Perpustakaan
For oil formations, helium and nitrogen are the most common gases used to measure the permeability of the
rock. However, recent approaches are based on the use of methane as it minimizes the properties difference
between the testing fluid and reservoir fluid. This work focused on the latter approach to compute the correction
of gas adsorption. The most widely used model is Cui et al. model that is based on Langmuir adsorption isotherm.
In this work, we introduced a modified model that is based on Freundlich isotherm. This model also includes the
correction for gas adsorption such as Freundlich isotherms proved to be more appropriate for the adsorption on
intact reservoir rock. The model is based on gas and rock properties and reduced pressure and temperature were
used to accommodate the gas compressibility. The modified model can also capture effective porosity of adsorption
( a) that can correct the pulse-decay storage capacity parameters a and b. The permeability estimation
of ultra-tight samples using the modified approach is enhanced owing to the correction in the storage volume
and rock porosity. Including the proper adsorption isotherm enhanced the porosity estimation because Langmuir
isotherm yielded 11% porosity and Freundlich isotherm yielded 12% porosity. Similar results were obtained in
the permeability estimation, Langmuir isotherm resulted in a 1.5% error compared to zero error in the
Freundlich isotherm estimation.