Combination of NMR and Ultracentrifuge Techniques for Effective Carbonate Reservoir Characterization

ABSTRACT

The combination of NMR and Ultracentrifuge techniques provides an easy and fast way of estimating the physical properties of rock/fluid systems such as wettability and irreducible saturation, capillary pressure and pore size distribution, fluid distribution in porous media and relative permeability curves. In this work, an extensive experimental program was conducted for the characterization of pores from some carbonate reservoirs and outcrops. During the experimental procedure, the difference between the mechanisms of rock/fluid and fluid/fluid interactions in restored state and natural state core was evaluated. As a result of our investigation it is established that the performance procedures provide the qualitative indication of adsorption of the heavy components of oil on the pore surface. Adsorption of the heavy fractions on a pore surface can take place not only in reservoirs containing heavy oil but also in light oil reservoirs with low concentrations of heavy fractions as indicated by the analysis of the recovered oil. Adsorption of the heavy components seems to take place predominantly in the largest pores which contain thinner films of irreducible water. This conclusion is made in view of similar work on cores with variable petrophysical properties. Modern laboratory systems and procedures, including NMR and Ultracentrifuge, provide the opportunity to estimate the changes of the thermodynamic conditions in a reservoir, at which additional adsorption of heavy hydrocarbon will not take place. Moreover, the procedures used in this work can be directed to increasing the hydrocarbon recovery efficiency.

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