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Integrated Interpretation of 3-D Seismic Data

Abstract

Abstract

Seismic data interpretation is one of the key tools used in the oil and gas industry for understanding the subsurface. Apart from providing excellent structural images, the compact sampling of a 3-D survey makes it possible to characterize reservoir and have an idea of the distribution of oil and gas within the reservoir.

The objective of the study was to integrate and interpret the available geological, petro-physical, 3D seismic and well data of the given field by tying well log data and seismic data, generating fault surfaces, petrophysical analysis, generating and time and depth maps and attribute analysis

We have worked on real data provided by ONGC of an area in Cambay basin. The log data for different wells was correlated with seismic data. Major steps included calculating reflectivity from sonic and density logs, converting reflectivity from depth to time and carrying out convolution to generate synthetic seismogram. Velocity model needs to be the robust one so as to have the uniformity in the time and depth map. For various inlines and crosslines, horizons were picked and faults were marked thereby building structural and stratigraphic maps. Thickness variation between two horizons is generated using isopach maps. This was followed by seismic attribute analysis to enhance the resolution of maps generated.

This study makes it possible to describe and appraise the reservoirs well and provides more confidence in locating exploratory inputs. Many structure related seismic attributes like ESP (Event Similarity Prediction), Coherence, Dip-Azimuth etc., provide very good information about the fault frame work and discontinuities of the field. Spectral Decomposition is a good method to identify subtle faults. Thus in this way, we created an overall image of reservoir which can be used to look for structural traps of hydrocarbons and determining the productivity of reservoir through further calculations using petrophysical data.