In the first edition of this book, we observed that it had been created to fill a need for a usable self-contained volume on hydrodynamics (and hydrogeology) that was written specifically for the petroleum industry, but could also serve the earth science community in general. When the first edition was published (1982), M. K. Hubbert, the father of petroleum hydrodynamics, was approaching the final stages of his very productive career. For this reason, the book served as a vehicle to amplify his concepts and spread and stimulate applications of some of his theories and methods throughout the exploration sectors of the petroleum industry. This was accomplished by blending discussions of Hubbert's concepts with some of the procedures used by industry specialists to answer practical oil and gas questions. The simple aim of the book was to bring this material to the fingertips of working geologists and geophysicists, who were evaluating the hydrocarbon possibilities in larger exploration regions or assessing the potential of small, local subsurface oil and gas prospects. It was also hoped that by treating areas of conceptual overlap between petroleum geology and ground water hydrology, workers in both disciplines would be brought into closer contact, resulting in mutual benefits gained through healthy scientific and technical interaction. This remains our objective in the second edition, although it has become apparent that additional material is needed to satisfactorily achieve it. The size of this volume reflects the new subject matter.