The potential source rocks and hydrocarbon-bearing reservoir rocks are present in Upper Palaeocene (Langpar Formation), Lower Eocene (Lakadong Member of the Sylhet Formation), Middle to Upper Eocene (Kopili Formation), and Upper Eocene-Lower Oligocene (Barail Formation) sediments in Upper Assam Shelf. In addition, hydrocarbons are also present in the shallower Lower to Middle Miocene (Tipam and Girujan Formations) sediments. This chapter discusses the recent developments and applications of geochemistry to study the source rocks and the oils in parts of the Upper Assam Shelf. The source rock pyrolysis instrument (e.g. Rock-Eval), used to determine hydrocarbon generation potential, organic richness, and maturity of the source rocks, has been described in detail. The use of an alternate maturity parameter, oxi Tmax, for organically lean rocks has also been discussed. Determination of kerogen kinetic parameters for converting kerogen to hydrocarbons in the source rock, using multi-heating ramp and single-heating ramp methodologies, and their other applications are described. The need to measure the kinetic parameters specific to the kerogen in the basin has been emphasized through examples from the Upper Assam Shelf. The results of the study using the above techniques have shown that the source rocks from Upper Assam Shelf are composed of Type II, Type II/III, and Type III kerogen, and are oil-prone, oil- and gas-prone, and gas-prone. The source rocks are immature or early mature based on the maturity parameter, Tmax. The maturity of the organically lean outcrop shales, from Disang-Barail Formations in the Naga Schuppen Belt, ranges from early mature to post mature, based on oxi Tmax. The kinetic parameters of source rocks from Upper Assam Shelf, measured using multi-heating kinetics, are discussed. Hydrocarbon generation characteristics of these source rocks, determined using their kinetic parameters, are different and cannot be modelled using kinetic parameters of standard kerogen available in petroleum systems modelling (PSM) software. Therefore, the kinetic parameters specific to the source rock under consideration should be used to calculate hydrocarbon generation during PSM studies in a basin. A quick method of computing kinetic parameters using a single pyrolysis run (single-heating ramp method) is discussed, which is useful to quickly determine the kinetic parameters of many samples. The legacy data on routine source rock pyrolysis can also be used. Applying this quicker method has helped identify different organofacies in a basin. The application of Gas Chromatograph-Mass Spectrometer (GC-MS) in oil to source rock and oil to oil correlation studies has been discussed. Biomarker analysis using Single Ion Monitoring (SIM) GC-MS studies shows that the source rocks for the oils from the Upper Assam Shelf are terrestrial in nature. The depositional environment for these source rocks is oxic to sub-oxic. Applying the technique of MRM (Metastable Reaction Monitoring) GC-MS to the biomarker study of these oils has been able to reliably identify and quantify biomarkers like hopanes, steranes, oleananes, and bicadinanes. The ratios of these biomarkers were used to differentiate between the oils accumulated in the Langpar reservoirs and the Lakadong reservoirs from the oils accumulated in the Barail reservoirs, the Tipam reservoirs and the Girujan reservoirs. The biomarker data indicate the presence of multiple source rocks in the basin, which is crucial for developing an efficient exploration strategy and building a better petroleum systems model. A mismatch in the maturity of the oils from Assam Shelf, measured using sterane and hopane biomarkers, could be due to the mixing of the oils of different maturities from multiple source rocks, accumulating in a reservoir.