What is it about?
Pore fluids can alter the elastic properties of porous subsurface rocks. Amplitude vs Offset, AVO, technologies aim at detecting this response by measuring the change in the amplitude of recorded seismic waves reflected at different angles from the subsurface and these can then be used to estimate fractional changes in different elastic parameters to map fluids in time and space. This paper compares the sensitivity of different elastic parameters and AVO attributes and introduces a template to differentiate different fluid types in Poisson’s Ratio versus LambdaRho cross-plots, which can be generated by using values from measured well logs or observed AVO. It also proposes a new seismic fluid indicator as LambdaRho Poisson’s Ratio multiplication.
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Why is it important?
Seismic fluid indicators are becoming increasingly important as the exploration portfolios of companies are moving to higher risk combination and stratigraphic traps. The presence of a strong fluid indication has implications on pre-drill prospect assessment, portfolio management and can lead to a higher chance of technical and commercial success. Such technologies also have applications in the appraisal and development of discovered resources, identifying bypassed pays in mature fields and in monitoring the produced fluids by time-lapse seismic. They can also be utilized in monitoring the diffusion of stored carbon dioxide in Carbon Capture and Storage projects in time and space.
Perspectives
Fluid discrimination from seismic observations can be performed using either reflectivity or impedance from inversion. Absolute properties derived from seismic by inversion are rarely available in regional studies, whereas relative elastic properties can be easily obtained and used. This paper shows how the reflectivity of different fluid indicators can be approximated from AVO parameters at various chi (χ) angles, enabling an interpreter to use them even when inversion products are not available. The fluid indicator proposed is highly sensitive to gas saturation and can be potentially used as fizz-gas discriminator.
Cem Menlikli
CNOOC International
Read the Original
This page is a summary of: Poisson's Ratio-LambdaRho rock physics templates and a study on sensitivity of different fluid indicators, Interpretation, July 2024, Society of Exploration Geophysicists,
DOI: 10.1190/int-2024-0003.1.
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