Reflection Signal Shape Analysis as a Tool for Tuning Effects Removal from Amplitude DHI Analysis

Hydrocarbon reservoir prospecting within thin-beded strata with variable geometry is difficult. Direct hydrocarbon indicator (DHI) analysis can lead to false conclusions. Seismic image depends not only on lithology of reservoir layers, porosity and hydrocarbon saturation but also on their geometry. Interference of reflected signal from top and bottom of a layer can result in increase or decrease of amplitude and causes change of wavelet shape.<br>Analysed seismic data include pinching-out Cenomanian sandstones (Cretaceous) composing the Mesozoic complex which creates base of the central part of the Carpathian Foredeep toward the east of Cracow (Poland).<br>The paper presents procedure that removes gains caused by pinching-out layers using the phenomena of wavelet shape variation within tuning zones. The procedure is based on construction of filters removing tuning effects form amplitude maps. In first stage the procedure was applied to synthetic seismic data (synthetic image of Rylowa gas reservoir). Positive results were obtained what allowed to apply filters to amplitude maps derived from recorded data.<br>Procedure application resulted in anomalies diminution what allowed to draw conclusions that some amplitude anomalies within studied area are caused by geometry of layers. <br>