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Determination of Moisture Adsorption Isotherm of Shale from Agbada Formation Using GAB Model

Author Affiliations

  • 1 Department of Petroleum and Gas Engineering, Faculty of Engineering, University of Port Harcourt, NIGERIA

Res. J. Engineering Sci., Volume 1, Issue (4), Pages 27-33, October,26 (2012)


Shales are susceptible of different phenomena, including swelling, shrinkage and hydration (shale instability); hence are impacted by moisture content. Moisture adsorption isotherms of shales from Agbada Formation were determined at 27°C over a water activity (aw) range of 0.30 to 0.96 using a Static gravimetric technique. Moisture adsorption isotherms of these two shale samples from well A and well B exhibited the sigmoid type II and V shapes respectively. The Guggenhein, Anderson, de-Boer (GAB) model was applied to fit the experimental data satisfactorily. A non-linear regression analysis method was determined to evaluate the parameters of GAB sorption equations. The criteria used to evaluate the goodness of fit to the model were Quadratic estimates, Central derivatives and Conjugate search of Microsoft Excel. The GAB model was used because it fit to the experimental adsorption data for a wide range of water activity (0.10 0.96) and the error square value calculated from Microsoft Excel was low. The estimated GAB parameters and constants were in good agreement with what the model dictates and with literature.


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