Impes modeling of volumetric dry gas reservoirs with mobile water

Date

2004-09-30

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Publisher

Texas A&M University

Abstract

As the importance of natural gas as a resource increases, the importance of volumetric dry gas reservoirs with mobile water as the dominant gas reservoir types will also increase. This research developed an efficient, user-friendly simulation program specifically designed to model two-phase flow of gas and water in these reservoirs. Since fluid compression and viscous forces are the dominant parameters that control fluid movement in a dry gas reservoir, we used the Implicit Pressure and Explicit Saturation (IMPES) formulation of flow equations in which neither gravity nor capillary pressure terms are pertinent. Therefore, the IMPES approach showed greater stability for all cases considered in this work. The developed simulator is a Visual Basic Application (VBA) code for which the users can obsereve the results in a pertinent Microsoft Excel file. This program allows users to study the depletion behavior of volumetric dry gas reservoirs with mobile water as efficiently and accurately as is now possible in more expensive commercially available reservoir simulators. The program was validated by comparing the results with a well-recognized commercial reservoir simulator (CMG). The results of a battery of tests of this simulator matched very well with results of the commercial reservoir simulator for all tested schemes including different simulation plans; reservoir, grid and fluid data; and well configurations. The observed applicability of the program suggests when dealing with volumetric dry gas reservoirs with mobile water there is no need to employ more expensive commercial reservoir simulators, as the program can reliably be used for any simulation scheme of this case. Furthermore, the program can later be applied in a more robust reservoir simulator as the part that handles dry gas cases.

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