Abstract
The concept of diagnosis used in this paper has a similar meaning as it used in well test analysis, and essentially refers to the identification, and its sequence as the exploitation time increases, of the production mechanisms of a gas reservoir.
This paper discusses an approach for the diagnosis of the gas reservoir production mechanism, derived from a general gas material balance equation (GGMBE), that considers the possibility that the reservoir could be naturally fractured: z/p vs (z/p)Gp. This diagnosis of the production mechanisms can be especially very useful for conditions where the reservoir characterization is limited. Once this diagnosis process has been accomplished, the original gas in place (OGIP) can be more accurately estimated through the present methodology, especially when combined with the available techniques (specific graphs, such as p/z vs Gp, Havlena and Odeh, etc.). In addition, this method allows the estimation of the cumulative effective compressibility, ce(p), of the associated water volume ratio, M, and of the water influx, We(t). The new method is illustrated through its application to the most discussed gas field behavior examples published in the literature, among them the McEwen's water influx case, the volumetric Begg's case and the overpressured Duggan's Anderson L case.
