Sandstone intervals of the Lower Goru Formation of the Cretaceous age are proven reservoir intervals in the middle Indus Basin, Pakistan. However, based on seismic data interpretation, it is difficult to differentiate payable gas sand from non-payable gas sand. Various types of post-stacks seismic attributes are extracted and analyzed to differentiate payable gas sand from non-payable. The analysis reveals that average instantaneous frequency, peak spectral frequency, average instantaneous phase and sweetness seem to be more effective attributes along with energy half time. Sweetness attribute map shows two sweet spot below the targeted window which indicate to the presence of gas play. Statistical analysis is also carried out to find the associations between seismic attributes and thickness of gas layer values. Cross plots of these attributes were quantified through regression analysis. A good correlation with regression coefficient (R 2 ) [ 0.78 is found between seismic attributes and gas layer thickness except average instantaneous phase attribute, which lays the foundation for predicting the thickness of gas reservoir.

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International audienceIn seismic applications, the bulk modulus of porous media saturated with liquid and gas phases is often estimated using Gassmann's fluid substitution formula, in which the effective bulk modulus of the two-phase fluid is the Reuss average of the gas and liquid bulk moduli. This averaging procedure, referred to as Wood's approximation, holds if the liquid and gas phases are homogeneously distributed within the pore space down to sizes well below the seismic wavelength and if the phase transfer processes between liquid and gas domains induced by the pressure variations of the seismic wave are negligible over the timescale of the wave period. Using existing theoretical results and low-frequency acoustic measurements in bubbly liquids, we argue that the latter assumption of "frozen" phases, valid for large enough frequencies, is likely to fail in the seismic frequency range where lower effective bulk modulus and velocity, together with dispersion and attenuation effects, are expected. We provide a simple method, which extends to reservoir fluids a classical result by Landau and Lifshitz valid for pure fluids, to compute the effective bulk modulus of thermodynamically equilibrated liquid and gas phases. For low gas saturation, this modulus is significantly lower than its Wood's counterpart, especially at the crossing of bubble point conditions. A seismic reflector associated to a phase transition between a monophasic and a two-phase fluid thus will appear. We discuss the consequences of these results for various seismic applications including fizz water discrimination and hydrocarbon reservoir depletion and CO2 geological storage monitoring

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Physical characterization study was carried out on limestones

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