The premise of this research is the concept, development, and application of an approximate relation for the material balance of abnormally-pressured gas reservoirs. The approximation is formulated directly from the rigorous material balance for the case of an abnormally-pressured gas reservoir. The primary assumption in this derivation is that WGp <1 or Ce(p)(pi-p)<1. Further, we can proceed by assuming that W is either constant or some arbitrary function. If we assume W=constant, then the following form results: At first glance there may be concern that this approximation is not sufficiently valid for field applications — however, we have shown this relation to be an extraordinarily accurate approximation of the rigorous material balance. This result is suited not only for use as a characteristic model, but also for use as a data analysis mechanism (i.e., this result is used to develop a suite of analysis plots, plotting functions, a type curve, etc.). In this work we provide the following new results: 1) A suite of 6 (six) plotting functions based on the p/z-Gp2 material balance model. 2) A suite of 4 (four) p/z-Gp performance plots which are used to calibrate analysis. 3) A new type curve in terms of a dimensionless pressure function (pD=(pi/zi-p/z)/pi/zi) versus a dimensionless cumulative production function (GpD=Gp/G), where the type curve solution is based on the new p/z-Gp^2 (a quadratic material balance) model.