Actually in Venezuela reservoir characterization has become very important, especially for heavy oil reservoirs because of the great amount of reserves located in the Orinoco belt. For this reason, new logging techniques like nuclear magnetic resonance are being applied in order to determine petrophysical properties of the reservoirs and fluid characteristics.

The transversal magnetic relaxation time or T2 has been measured to determine the T2 cut-off and fluids saturations of unconsolidated core plugs samples from Melones field. Also the T2 distribution has been measured in heavy oil hydrated and dehydrated samples from Hamaca and Melones fields in the laboratory at different temperatures to obtain the viscosity based on the distribution fitting to gaussian curves.

The effect of temperature increase on heavy oil and water saturated core plugs contributes to a decrease of the oil viscosity, which is observed as a shift of the oil signal to higher T2 times, while the water signal decreases.

The NMR response of core plug samples, saturated with heavy oil, heavy oil with gas in solution and gel is used for calculating the oil and gel saturations, irreducible oil saturation, porosity and the oil volume displaced by gel.

This work presents some of the applications of NMR techniques for a better understanding of the heavy oil reservoirs.

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