AAPG Geoscience Technology Workshop

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The Myra – Sara Reservoir Characterization Project


Quantitative seismic interpretation (QSI) integrates well and seismic data with rock physics to predict reservoir parameters and to quantify reservoir properties such as lithology and fluid type. QSI has become an essential tool for reducing risk associated with drilling and to improve the accuracy of predicting hydrocarbon and other pore fluid distributions. QSI is performed using a combination of advanced techniques, such as forward modeling of well data, model based AVO analysis and elastic inversion. In this study we demonstrate a detailed investigation of the data from Sara and Myra blocks, located in the East Mediterranean Sea. The objective of the project was to undertake a detailed QSI analysis of the Mira- 1 well data and associated seismic in order to predict hydrocarbon saturation at the location of the planned Sara-1 well. The time table for the analysis was very tight as drilling commenced on Sara-1 at the same time as the analysis was carried out. To predict hydrocarbon saturation, several techniques were used using Paradigm software. The Fluid Factor and Gradient data was investigated for high amplitude AVO anomalies in the target location. Normal Incidence and Gradient data was cross-plotted and anomalous trends have been identified. Fluid substitution was performed on Myra-1 well data in the Tamar Sand formation using Gassmann theory. Fluid substitution modeling is an important tool in reservoir characterization as it predicts a specific fluid response. Cross-plotting for fluid substituted P and S impedance logs was performed and compared with cross-plotting using the original logs. Simultaneous inversion of prestack data with analysis for low Vp/Vs ratios were also analysed as possible hydrocarbon indicators.The results of all these analysis were then used to map potential hydrocarbon zones at the planned Sara-1 well location. The use of multiple QSI techniques as outlined above, enabled a more reliable prediction of the presence of hydrocarbons. The conclusion from all workflows was that there are no seismic derived indicators in the Tamar Sands suggesting an absence of hydrocarbons. A good match between seismic data and synthetic seismograms, obtained from Myra-1 well logs was a positive indication to the reliability of the seismic based analysis for fluid content. This prediction was confirmed during the drilling and subsequent analysis of the Sara-1 well data. The final conclusion was that there is no indication for gas in Tamar Sands at the Sara-1 location.