AVO Products
Amplitude Variation with Offset (AVO) is a pre-stack interpretation technique to indicate rock lithology and fluid content. To qualify the presence of oil and gas, AVO trends will be measured on pre-stack time migrated data, and compared to model or known field examples. The use of AVO attributes in conjunction with high resolution migrated stacked data has resulted in numerous successful exploration and development wells worldwide.
In recent years, PGS has developed several technologies to exploit very long offset amplitude information and anisotropic velocity behaviour in seismic data to optimize the success of AVO pursuits. PGS believes that proper QC is fundamental to any high-end data analysis, and uses the QC programs AVOPREP and AVOQC to ensure correct parameter selection.
PGS believes that in order to achieve optimum AVO results, the data must first be processed in a manner that will preserve all the recorded amplitude and phase characteristics. PGS has developed algorithms that can be employed to achieve a high-quality image, whilst preserving the full amplitude integrity. Once this has been achieved, the processing continues with added QC to ensure optimum parameter selection for the AVO analysis.
The following image illustrates the importance of achieving an optimum flattening of the reflection event within each gather. PGS algorithms have options for high-order move-out corrections (up to 6th order in TAPSTM), as well as the ability to compensate for anisotropy.
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Long Offset AVO (LNMO) |
Pre-stack time migrated stack
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Fluid factor anomaly, gas reservoir
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Any AVO, seismic inversion, or Reservoir Characterisation exercise requires three fundamental data characteristics to maximize the robustness and accuracy of the results:
High signal-to-noise (S/N) ratio, including the moval of all multiples
Large frequency bandwidth, particularly the availability of low frequencies
High spatial continuity of all target seismic events
The PGS HD3DTM data product provides the optimum platform for satisfying all three of the above criteria. As a direct result of proper seismic wavefield sampling and target illumination, preferably complemented by overlap shooting, 3D SRME will achieve the best possible removal of all multiple energy. Data quality and resolution will be maximized, and any reservoir geophysical studies will have the lowest risk.
The following image illustrates the computation of the Fluid Factor, which is a function of how the A (Intercept) and B (Gradient) attributes vary within the seismic volume, with reference to a background trend.
The following images are example AVO diagnostics.
Class II AVO stack (left) and Hidden Class II AVO stack (right).
Fluid Factor stack.
