Dispersivity as an Oil Reservoir Rock Characteristic

Donald E. Menzie, Subijoy Dutta, R. S. Shadizadeh, M. A. El-Ageli

Dispersivity is identified as a measure of the ability of a rock to allow mixing of two fluids inside a porous medium and is experimentally determined in this study. It is found to vary with other physical properties of a rock, such as porosity and permeability. Dispersion coefficient and dispersivity of rocks were found to increase with higher permeability of the rock. An empirical relationship between the permeability and the dispersion coefficient of a rock has been developed from the results of this experimental study. Dispersion characteristics of different cores have been correlated with Koval's heterogeneity factor (H-factor) from the results obtained in this study. An empirical equation for viscosity correction to obtain a standard dispersion coefficient of a rock has also been developed. A standard dispersion coefficient is defined to be the dispersion coefficient obtained experimentally when the ratio of viscosities of the two fluids are the same.

Based upon the results obtained in this experimental investigation, it is evident that the dispersivity of a reservoir rock is one of the factors governing the areal and vertical sweep efficiency during an EOR flooding process. Knowing the dispersivity of a reservoir rock, the solvent slug size in hydrocarbon miscible flooding can also be determined. In selecting the reservoir for EOR and the specific EOR process, evaluation of the dispersion characteristic of the reservoir rock appears to be a factor of paramount importance.

In the present investigation the study of dispersion mechanism is limited to a miscible flooding process. Extension of this study also includes immiscible flooding processes and correlation of dispersion characteristic with relative permeability and capillary pressure curves of oil reservoir rocks.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.