A fast and accurate method for ihe group analysis of crude oils in porous media that describes petroleum components (especially heavy f;ocrions) has been developed NMR structure group anabsis is used as ihe tool for the characterization of crude oils. This method is proposed as an alternative io existing complicated and laborious methods of characterization of extracted oil samples. Currenily, group analysis of heavy fractions of crude oils is being investigated by means of chromatographic method such as the SARA (saturates-aromatics-resins-asphaltenes) test These methods are usualb expensive and require considerable work from qualzified personnel. Furthermore, these metho& cannot be used for estimating the oil components in-situ.