Abstract

Application of seismic interpretation for fluid detection in carbonate reservoirs has been a major challenge for researchers in the past few decades. In this context, many approaches have been introduced, but they failed to be effective enough in the presence of different pore types in carbonate rocks. On this basis, we have developed a novel method called full-angle extended elastic impedance (FEEI) analysis as an alternative to seismic interpretation for fluid detection. Investigating the entire trend of changes in extended elastic impedance (EEI) values with χ angles (the intercept-gradient coordinate rotation angles), FEEI analysis can efficiently discriminate fluid types in carbonate reservoirs. The first steps in the application of the proposed method include performing fluid substitution modeling and making FEEI templates using FEEI analysis for different saturation scenarios. Subsequently, the derived FEEI method was subjected to validation and verification based on a carbonate case study with five existing wells drilled into a zone containing oil and brine. Next, we inverted the prestack seismic data to EEI data at corresponding χ angles, followed by interpreting the resultant EEI data by FEEI templates. Comparisons between the obtained EEI-inverted sections indicated the robustness and reliability of the proposed approach in estimating the type of pore fluid in the selected carbonate interval. Finally, estimation results were successfully tested on a blind well, which ended up with promising results, and we discuss the uncertainties associated with this methodology. The findings of this research include the introduction of a novel EEI template (i.e., FEEI template) and two new rock-physics templates for fluid detection, with the considered case study confirming the applicability of the proposed FEEI in a carbonate field.

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