A high-amplitude anomaly was identified in the Upper Oligocene Daman Formation clastic sequence during initial interpretation of newly acquired 3D seismic data in the Tapti-Daman sub-basin offshore western India. This anomaly exhibited the depositional signature of a channel and was interpreted as bright spots associated with gas sands, consistent with the occurrence of thin gas pays in the sandstone reservoirs of Daman Formation in the area. Considering thickness and areal extent, thick gas sands were predicted, upon drilling; however, thick water-bearing sands were found. The predrill interpretation was mainly based on windowed amplitudes without validation through character of reflection events and other supporting evidence such as frequency, velocity, and AVO.

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The 3-D seismic data of NE-Panna and adjoining area within Central Graben in Heera-Panna-Bassein Tectonic block of Bombay Offshore Basin, India, have been evaluated for identification of prospects within Middle to Upper Eocene Sequence (Bassein Formation) which is hydrocarbon bearing in near by areas. In the study area, massive to laminated carbonate sections without hydrocarbons were encountered in three wells, which were drilled on the basis of 2-D seismic data interpretation. Subsequently 3-D data was acquired in 2004 to assess the reservoir and trap potential of the area.The 3D seismic along with other geo-scientific data of the area have been integrated and interpreted by applying concepts of seismic stratigraphy, seismic attribute analysis and 3D visualization techniques. On the basis of seismic reflection configuration and interpretation of electrolog facies, the Bassein Formation has been divided, seismically, into four units which were deposited under transgressive to highstand regime including late highstand sea level fall. Within units, coeval deposition in different sub-environment has been inferred from the lateral seismic facies variation. Seismic impedance volume generated through model based post-stack stratigraphic inversion, seismic attributes and attributes derived from logs, e.g., %limestone and porosity, were analysed with geostatistical cross-plots method to understand the interrelationship between lithofacies and seismic facies. Moderate to high amplitude and moderate impedances have been found to be associated with carbonates having good porosity. The lateral discontinuities and boundaries between different assemblages have been mapped with 3D visualization of volume and surfaces coupled with coherency slices. Various facies assemblages representing carbonate buildups, off-buildups at slope of big buildups and wedges of debris flows (talus) were identified with consideration of structural configurations, attributes and impedance, and depositional geometries. The inferences of this study are validated at drilled wells.

Sandstones associated with Oligocene Barail coal-shale sequences form good reservoir facies and are oil producers in many wells of India's Geleki Field and adjoining areas. Mapping these sands using seismic attributes may lead to data that are difficult to interpret because sand-coal and shale-coal interfaces generate similar attributes. In such cases, seismic attributes may show the depositional geometry but with ambiguous lithology. The lithologic ambiguity may further be worsened by carbonaceous shales, which often occur in coal-shale sequences, and that shales may appear similar to sandstones in some log (e.g., gamma ray, resistivity, etc.) and interface properties. Integration of logs with seismic data improves lithologic discrimination and reservoir characterization. The log motifs (patterns) reinforce the interpretation of depositional environments and processes and log properties (magnitude) reduce the ambiguity in lithologic prediction. Seismic attributes and log properties can be integrated by finding interrelationships between these two types of data at control (wells) points. The interrelationships are used for seismic-guided prediction of log properties beyond the wells and generation of property volumes. The predicted volumes are interpreted in terms of lithology and other reservoir parameters (porosity, saturation, etc.).

Commercial gaseous hydrocarbon has been established from multilayered reservoirs within the Bhuvanagiri Formation in the Ariyalur-Pondicherry subbasin, but sustained production is obtained from only a few wells of the Bhuvanagiri Field. This has necessitated developing an integrated depositional model dovetailing distribution of favorable reservoir areas of the Bhuvanagiri Formation within the subbasin. Root-mean-square amplitude attributes and spectral decomposition attributes, along with RGB blending of spectral slices at different frequencies, have revealed a conspicuously northeast-southwest-trending channel within the Bhuvanagiri Formation. From well, sedimentological, and biostratigraphic data analysis, a deepwater turbidity channel model for the Bhuvanagiri Formation has been postulated. Deciphering the facies distribution pattern vertically and laterally within the turbidity channel is often complex and challenging. Integrated analysis of available laboratory data, petrographic, and scanning electron microscopy studies indicate poor porosity and permeability because of clay coating on grains, occurrence of authigenic clay as pore fill, cementation, and other diagenetic changes that have made reservoir characterization increasingly challenging. Four major lithofacies assemblages have been identified: basal lags, slumps and debris flows, arenaceous coarse-grained stacked channels, and fine-grained channel levee with characteristic log and seismic responses. To characterize the lithofacies, various crossplots have been generated by using processed logs to derive interrelationships between reservoir facies and log impedance. A model-based inversion has been attempted, which resulted in fairly satisfactory output with likely discrimination of reservoir and nonreservoir in an unexplored area within the field. The outcome would facilitate further exploration and delineation activities within the Bhuvanagiri Formation in the Ariyalur-Pondicherry subbasin.