Pressure transient analysis for multilayered gas reservoirs under various reservoir conditions

Abstract

Most reservous are heterogeneous in nature, Reservoir heterogeneity can be in the vertical direction (layered reservoirs) as well as in the radial direction (composite reselyoirs). Fluid flow is oomphealed for the gas reservoirs because of the inertial and turbulence effects and the pressure dependence of gas properties, Tills study develops a semi-analytical model for pressure transient analysis of heterogeneons gas reservoirs. Reservoir heterogeneity has been considered by drawmg upon the layered and composite nature of the reservoirs. The diffusivity equation has been solved as a generalized eigenvalue problem utilizing the pscudopressure and pseudotime schemes. The model takes into account the high velocity effects, wellbore storage and skin, and different possible inner and outer bOlUldary conditions. Finite formation damage can also be modeled. The model has been validated by comparing the results with those of some analytical models and simulation results published in the literature. Different schemes for calculating high velocity effects have been studied and evaluated. For the same amount of skin, both thin and !inite damaged zone responses have been compared. Both these responses have been fOlmd to be quite different for certain cases. AU possible outer boundary conditions, partial penetration and bottom water cond,tions may be studied. Its application is enormous in the field of pressure transient analysis of gas reservoirs. This versatile model, to my knowledge, includes more features for gas reservoirs than any other previously published pressure transient models.