The oilfields of North-East India is regarded as one of the oldest oilfields in the world. Crude oil is being produced from North-East India for more than 115 years. Prior to 1989, oil was produced from Girujan (upper to middle Miocene), Tipam (lower Miocene) and Barail (Oligocene) formation. Since 1989, oil is being produced from Sylhet limestone and Langpar (Eocene) formation in increasing quantities. All these oils are waxy in nature. They have a wide range of API gravity and pour point. Modern analytical techniques like HPLC, MPLC, TLC-FID, FT-IR, NMR (1H and13C) spectroscopy, HTGC, GC-MS, X-ray diffractometry, Interfacial tension, HPLC, UV-Visible spectroscopy, differential scanning calorimetry, thermo gravimetric analysis, Rock-Eval analysis and pyrolysis Gas chromatograph-mass spectrometry were used to understand the chemical composition of the heavier fractions of these oils. A new Geochemical analysis technique i.e. pyrolysis of asphaltenes and using aromatic biomarkers like alkyl naphthalenes and alkyl phenanthrenes produced as a result of pyrolysis of asphaltenes is introduced.