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Previous HitTimeNext Hit-Previous HitVaryingNext Hit Waveform Representations as an Aid for Identification of Uncertainty Related to Seismically Tuned Events in the Presence of Hydrocarbons


The identification of areas where seismic tuning is prevalent is important for the evaluation of subsurface structure and the de-risking of potential prospects. The “non-unique solution” to tuning given the presence of hydrocarbons is a problem that is well known in exploration. Typical AVO analysis that has been generally predictive of the AVO Class of a response, and has been used perhaps as a Direct Hydrocarbon Indicator (DHI), has limited utility in areas with seismic tuning. Various measures for detuning of the data have been proposed, but quantifying the uncertainty from the simultaneous changes in thickness and hydrocarbon saturation, along with potential changes in a myriad of other reservoir properties, have also remained elusive. It can be shown using rock physics models that for in-situ reservoir conditions that the Previous HittimeNext Hit-Previous HitvaryingNext Hit waveform-character is unique for AVO-responses that have the same intercepts and gradients, and would be otherwise considered “non-unique”. For a particular reservoir, the wedge Previous HitmodelNext Hit idea can be extended such that a large number of scenarios can be constructed that encompass the range of conditions present in the potentially tuned reservoir. Through the use of rock physics-constrained forward models, a corpus consisting of most likely to be encountered “non-unique” scenarios may be constructed. It can also be shown that in areas where tuning may be a concern, extracting waveforms and comparing them to patterns contained in the corpus, these rock physics derived waveform-character changes can produce maps of uncertainty that are more directly related to the simultaneous changes in the properties of the reservoir. These results may not only aid the interpreter in de-risking potential prospects in AVO-analysis, but also may provide the basis for a form of seismic inversion that utilizes the Previous HittimeNext Hit-Previous HitvaryingTop spectral representations within the corpus, to invert simultaneously for tuning thickness and hydrocarbon saturation.