Abstract
For the modeling of complex reservoirs with strong heterogeneity, for instance the deeply buried paleokarst reservoirs in the Tarim Basin, the traditional method by lateral interpolation and extrapolation of measured logs between well locations with the guiding of interpreted seismic horizons is driven by distance and often leads to non-geologic solutions, while the past improvements via adding seismic velocities or attributes information are still not accurate due to the resolution limitation or AVO (amplitude versus offset) effects contamination. In this paper, we present an amplitude-based modeling method by utilizing the heterogeneous information from seismic data to guide the geological model construction, based on the inverted pure P-wave data which have removed the AVO effects. The proposed method is applied in the impedance inversion of the paleokarst carbonate reservoirs in the Tarim Basin, where the reservoirs are characterized by substantial heterogeneity. Both the constructed Low frequency model (LFM) and the inverted impedance results of proposed method are more correlative with drilling data than that of traditional method. This method is more beneficial for strong heterogeneous reservoirs description especially in well insufficient or absent areas, suggested by the comparisons with traditional methods in the ZG8 area.
Highlights
Seismic data are routinely inverted into the relative impedance to provide quantitative predictions of reservoir properties-such as porosity, lithology fluid content etc., under specific conditions (Cerney & Bartel, 2007, Pedersen-Tatalovic et al, 2008)
It has to be further transformed into the true absolute impedance for reservoir properties predictions away from well control, via merging reliably low-frequency information of the constrained low frequency model (LFM) (Cerney & Bartel, 2007; Pedersen-Tatalovic et al, 2008; Zou et al, 2013; Grant, 2013)
The Ordovician carbonate reservoirs in this field are deeply buried (>5000m) (Yang et al, 2010) and characterized by strong heterogeneity and some degree of anisotropy. These reservoir spaces are formed by a product of complex karstification related to unclear paleokarst drainage systems and subsequent complicated tectonic disruptions during burial (Zeng et al, 2011; Sun et al, 2012; Zhang et al, 2011a; Zhang et al, 2011b). To reasonably describe this strong heterogeneous reservoir and achieve accurate properties for prediction, we propose an amplitude-based modeling method by utilizing the heterogeneous information from seismic data to guide the geological model construction, based on the inverted pure P-wave data which have removed the AVO effects
Summary
Seismic data are routinely inverted into the relative impedance to provide quantitative predictions of reservoir properties-such as porosity, lithology fluid content etc., under specific conditions (Cerney & Bartel, 2007, Pedersen-Tatalovic et al, 2008). These reservoir spaces are formed by a product of complex karstification related to unclear paleokarst drainage systems and subsequent complicated tectonic disruptions during burial (Zeng et al, 2011; Sun et al, 2012; Zhang et al, 2011a; Zhang et al, 2011b) To reasonably describe this strong heterogeneous reservoir and achieve accurate properties for prediction, we propose an amplitude-based modeling method by utilizing the heterogeneous information from seismic data to guide the geological model construction, based on the inverted pure P-wave data which have removed the AVO effects. The proposed method is applied in the impedance inversion of the paleokarst carbonate reservoirs in the ZG8 area, Tarim Basin
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