Estimation of reservoir lithology in field “A” using modeling of anisotropy parameter

The heterogeneity and anisotropy of rocks in the field is a necessity. Moreover, the existence of clay and carbonate sediment in Indonesia almost dominate the existing oil and gas reservoir. Ironically, the processing of seismic data is still much done by treating reservoir rocks as an isotropic homogeneous medium. Inaccuracies of results, therefore, always haunt the failure of exploration. Hockey stick phenomenon is the result of anisotropic medium that often appears on the far offset. Demand for the implementation of an anisotropic rock medium is now increasing and more important amid the exhaustive oil and gas reserves. NMO correction by using hyperbolic travel time on anisotropic media still displays the phenomenon of hockey stick at the remote offset. Usually this phenomenon will be muted on the processing of seismic data with the approach of isotropic earth models. This will result in the loss of some lithologic information. Therefore, this study was conducted using anisotropic approach to reduce residual moveout for data which has a very long offset. The method is to calculate the anisotropy parameter model of η which is controlled by core data. The results of this study showed that the Alkhalifah and Tsvankin method of non-hyperbolic travel time was better in the NMO correction for anisotropy medium with a long offset compared to the method of hyperbolic travel time. In addition, Alkhalifah and Tsvankin method can also estimate the lithology of a reservoir. The value of anisotropy parameter η from the equation itself has the same pattern as the gamma ray log. In reservoir, the sand has negative η value and shale has positive η value.