The book on Petroleum Geochemistry the first of its kind in India, is useful for postgraduate students of Science (Geology, Applied Geology, Geophysics, Earth Sciences) and undergraduate students of Engineering and Technology (BE, B.Tech.) undertaking several courses in petroleum science and engineering in the Universities, IIT's and other Institutions. It is also useful to geoscientists, engineers and technologists working in the oil industries dealing with exploration, production and related aspects. The book provides basic information on geochemical processes involved in petroleum generation, migration and accumulation in sedimentary basins, maturation of source rocks, evaluation of their genetic potential and correlations. It deals with the principles and applications of sub-surface geochemical methods including high resolution geochemical technologies for delineation of hydrocarbon kitchens and surface geochemical prospecting of hydrocarbons for prioritising targets for future exploration. In addition to basic principles, the book deals with the occurrence and distribution of petroleum in worldwide sedimentary basins with special reference to Indian basins, geochemical basin modeling and its application to petroleum exploration, application of biomarkers and modern instrumental techniques for characterisation of organic matter in source rocks and identification of their depositional environments. Applications of oil field waters and their role in enhanced oil recovery (EOR) operations, implications of scale formation and corrosion on drilling equipment and other installations are described comprehensively. Apart from conventional oil and natural gas the need for exploration and exploitation of unconventional petroleum resources such as Coal bed methane (CBM), Gas hydrates, Bituminous sands, Shale gas and Oil shale, Basinal gas and Tight gas sands, their origin, occurrence, characterisation of depositional environments, exploration and production strategies, environmental concerns and worldwide distribution with special emphasis to India are elaborated in detail.