The Material Balance as an Equation of a Straight Line

Abstract

The material balance equation used by reservoir engineers is arranged algebraically, resulting in an equation of a straight line. The straight line method of analysis imposes an additional necessary condition that a successful solution of the material balance equation should meet. In addition, this algebraic arrangement attaches a dynamic meaning to the otherwise static material balance equation. The straight line method requires the plotting of one variable group vs another variable group. The sequence of the plotted points as well as the general shape of the resulting plot is of utmost importance. Therefore, one cannot program the method entirely on a digital computer as is usually done in the routine solution of the material balance equation. If this method is applied, then plotting and analysis are essential. Only the appropriate equations and the method of analysis and interpretation with comments and discussion are presented in this paper. Illustrative field examples for the various cases treated are deferred to a subsequent writing.