Integrated 3D Seismic Modelling Of Lower Goru Sands In Gambat Latif Blocks In Pakistan Based On Structural Interpretation,Sequence Stratigraphy, Seismic Attributes And Facies Analyses

Abstract

Reservoir properties are essential for quantitative and qualitative reservoir evaluation. Although the interpretation of seismic data and petrophysical analysis of well logs provides a crude analysis of the reservoir, the spatial distribution of reservoir characteristics is essential for economical exploitation. The objective of this study is to characterize the spatially distributed reservoir properties of Lower Goru sands over a vintage 3D seismic data in Gambat-Latif block, Lower Indus Basin, Pakistan, using structural interpretation, attribute analysis, inversion, and Lambda-Mu-Rho (LMR) attributes. C Sands has been identified using well to seismic tie, with horizons picked on the 3D seismic data. Interpreted seismic volume shows presence of faults in subsurface, with faults oriented in a NW-SE direction, and marked horizons of interest as shallow in west and deeper in the east, with deposition of facies also showing a thickening trend towards east. Petrophysical analysis conducted in both the wells, out of which two zones of interest were marked in Tajjal-02 well showing an average high effective porosity in Zone-1 ranging from 11-12 %, and in Zone-2 ranging from 7-8 % and water saturation in Zone-1 ranging from 74.97-75 %, and in Zone-2 ranging from 80-81 %. The inverted acoustic impedance volume identified the gas sand lithology and confirmed the presence of fluid in the C sands using model-based inversion and lambda-mu-rho attribute. The picked horizons have been used to mark the spatial distribution of the quantitative reservoir properties. Model based inversion depicts low acoustic impedance anomalous zones in the sands of C Sands indicating the presence of hydrocarbons. The mu-rho attribute spatially indicates low to moderate values confirming the presence of sands, while the lambda-rho attribute, sensitive to pore fluids, confirms the presence of oil saturated sands of C Sands. A new location has been proposed for drilling well where there is a potential prospect zone based on the analysis. The proposed location has low impedance values, low to moderate Mu-Rho values and low Lambda-rho values all supporting the presence of hydrocarbon accumulation. DRSML QAU 12 The Electrofacies have been generated from the well log data indicating four facies namely, gas sand, shaly sand, sandy shale, and shale. Gas sands are observed in the well with the help of electro facies. Sequence stratigraphy is applied on well data and sequences are marked with the help of well logs. The result indicates a zone in Tajjal -03, two Zones in well Tajjal-02 and two zones in well South Tajjal-01