Abstract

Deltaic sands of Mid-Eocene age are hydrocarbon bearing in Nada field of Cambay basin. The greater depth of burial, lesser thickness of reservoir sands and their discrete nature of occurrence limit the seismic imaging, making precise mapping of individual pay sands a challenging task. This problem is tackled effectively by using interpretive processing tools such as Stratigraphic inversion and pseudo log volume analysis. In the first step, the 3D seismic data are inverted to acoustic impedance (AI) volume. The seismic data is then transformed to pseudo-sonic log volume in the next step by using various seismic attributes, including AI. Horizon time slices corresponding to Nada Main pay and Nada Upper pay sands of the study area in the AI and pseudo sonic log volumes are analysed. The horizon slice of Nada Main Pay sands shows that these sands are deposited as distributary mouth bar, probably acquired a discrete lobe geometry, due to reworking by wave action. Nada Upper Pay sands are inferred to be distributary channel deposits in the eastern part of the area. The pseudo-sonic log property is found to be better discriminator of reservoir sands when compared to AI.