MULTIATTRIBUTE INVERSION AND AVO ANALYSIS FOR RESERVOIR CHARACTERIZATION OF GAMBAT AND LATIF BLOCK, SOUTHERN INDUS BASIN, PAKISTAN

Abstract

The Tajjal field is located in Lower Indus Basin, Pakistan, and the B-interval of Lower Goru is the main reservoir of Cretaceous age. Variations in reservoir quality are the main risk that depends on the number of properties. Porosity is one of the main properties which was evaluated throughout the 3D seismic data cube of the field instead of well location only, by adopting a multi-linear regression method and was later, used for designed the reservoir property at well location by doing AVO analysis. In this integrated approach for reservoir characterization, the petro-physical analysis was performed on three wells drilled in the Gambat-Latif block. Tajjal-01 encountered a 9.9m hydrocarbon-bearing zone with effective porosity of 6.38%, Tajjal-02 encountered a 5m hydrocarbon-bearing zone with effective porosity of 12.87% and Tajjal-03 encountered a 4m hydrocarbonbearing zone with effective porosity of 8.21%. Then multi-attribute inversion was done which displayed low impedance values dominantly for sands of B-interval data and showed that there were least differences between the seismic data derived porosities and well log derived porosities for the top sands’ layer. Hence, this was considered to have a dominant impact on P-impedance. Lastly, AVO modeling was only done for Tajjal-01 well due to data limitations and Class I & IV anomaly was found in top sands of B-interval. Hence, top sands of B-interval were confirmed to have a good reservoir quality.