Reservoir diagnosis and reserve estimation for bakhrabad gas field using production data

Abstract

The Bakhrabad gas field i~ an old and matured gas field in Bangladcsh, whieh is producing since 1984. This thcsis presents a systematic diagnosis of reservoir behavior of this gas field with respect to. different flow regimes, reservoir connectivity or compartmentalization, rcscrvoir drive meehani~m, estimation of reserve, and nature of production decline. Production data such as flowing wellhead pressure and production rate are used in different simple diagnostic tools like pressure VS. rate, decline and appwximaled wellhcad material balance. The same data is also analyzed with different type curve methods including Fetkovich, Blasingame, Agarwal-Gardner, and Normalized Pressure Integral (NPI) type curves. Commercial production analysis (PA) software is used for this purpose. Pressure VS.ratc diagnosis reveals reservoir flow behavior with approximate duration of flow regimes for t.hewells of respective sands of Bakhrabad gas field. It is found that Pseudo-Steady State (PSS) flow regime is currently dominating in all pwducing sands. No compurtmentalization is detected in any of thc producing sands. Decline diagnosis shows exponcntial type of production decline in all major sand~. Approximate wellhead material balance diagnosis indicates volumetric depletion as the drive mechanism for this field. Type eurve analysis show good agreement between production dala and the aswmcd radial reservoir model for this field. The Gas Initially in Place (GIIP) estimated by different methods range from 916 to 1263 BCt', with the most likely value being 1200 BeF. These values compare well with thc previously reported valucs based on volumetric method, whieh ranges from 1281 to 1392 BCF. Assmning abandonment at 600 psia, the estimated recovery factors range from 53% to 73%.