One of the most common, economical and reliable sources of information to determine the commercial productivity, the formation characteristics, and well conditions is the pressure transient test. However, the pressure transient test must be properly designed, run, and interpreted to provide the desired information.
The pressure transient data are usually interpreted by plotting the pressure versus time on semi-log paper. The semi-log interpretation method is often impractical due to difficulties associated with identification of the correct straight line. Type curves provide a more general method of interpretation. In this method, a plot of pressure versus time on a log-log paper is utilized to obtain a graphical match (solution) with the type curve. The log-log plots, however, then to minimize the differences in the shape of the various type curves. Therefore, a unique solution is often difficult to obtain, especially when the well test is short.
This paper introduces a methodology for interpreting well test data by utilizing more sensitive semi-log type curves. The semi-log type curves are useful for verifying the uniqueness of the solution. The methodology has been explained and discussed through several examples utilizing published well test data.