Advances in well test analysis during the 1980"s and 90"shave been associated with: (a) the use of pressure derivative plots, (b) the common availability of computer software for rapid graphical presentation, (c) the use of non-linear regression (automated type cure matching), (d) the availability of higher precision, high frequency data, both for pressure and flow rate, and (e) the development of new interpretation models, such as for horizontal wells, layered reservoirs and multiphase flow. This book takes the form of a tutorial emphasizing these aspects of well test interpretation in this new computerized environment. During the book, emphasis is on problem solving, using computerized tools. A companion website link contains full listings of the data used in many of the examples, as well as a hypertext searchable version of the entire book (in the form of a Windows™ Multimedia Viewer title). A well test interpretation software program on the website link allows you to work with the example data yourself to learn more about how well test interpretation is achieved in practice (Windows XP and earlier only).