* Corresponding author: syamsu.rosid@ui.ac.id Reducing Residual Moveout for Long Offset Data in VTI Media Using Padé Approximation Indah Nur Pratiwi 1 , Mohammad Syamsu Rosid 1,* , and Humbang Purba 2 1 Departement of Physics, Faculty of Mathematics and Natural Science, University of Indonesia, Depok-Indonesia 2 PPPTMBG LEMIGAS, Jakarta-Indonesia Abstract. Modification of the hyperbolic travel time equation into non-hyperbolic travel time equation is important to increase the reduction residual moveout for long offset data. Some researchers have modified hyperbolic travel time equation into a non-hyperbolic travel time equation to obtain a more accurate value NMO velocity and parameter an-ellipticity or etha on the large offset to depth ratio (ODR) so that the residual moveout value is smaller mainly in large offset to depth ratio. The aims of research is to increase the reduction value of error residue at long offset data using Padé approximation then compare with several approximations. The method used in this study is to conduct forward modeling of the subsurface coating structure. The results of the three-dimensional analysis show that the Padé approximation has the best accuracy compared to the other travel time equations for ODR value up to 4 with an-ellipticity parameter is varying from 0 to 0.5. Testing of synthetic data for single layer on vertical transverse isotropy (VTI) medium obtained the maximum residual error value produced by the Padé approximation is 0.25% in ODR=4. Therefore, Padé approximation is better than other methods for reducing residual moveout. Keywords: Residual Moveout; Long Offset; Padé Approximation; Anisotop Medium 1 Introduction Technology in oil and gas sector in Indonesia is not good enough. Whereas oil reserves are running low. Some of the factors needed to find new oil reserves are to add information from seismic data obtained. Processing and interpretation of seismic data usually assume a homogeneous isotropy medium. However, the real subsurface are generally heterogeneous anisotropy medium. Anisotropic properties of rocks can be seen at the Normal Moveout (NMO) correction. The aim of NMO correction to eliminate the effect of distance. The NMO correction depends on offset and velocity. The problem caused when Normal Moveout (NMO) correction is the stretching effect. The trigger for stretching effect is influenced by frequency attenuation of seismic waves experienced by incoming ray velocity received at a far offset [1]. The effect caused when seismic data acquisition was done at a long offset is non-hyperbolic moveout [2]. The non-hyperbolic that appears is a hockey stick caused by anisotropic factors that occur in subsurface of the earth so that it cannot be reduced by NMO correction with hyperbolic travel time equation. The inaccurate selection of normal moveout (NMO) velocity will cause a normal moveout residual. This problem can be solved with the muting of data in the processing, but it can affect the loss of information in subsurface such as lithology, fluid, etc [1]. Non-hyperbolic travel time equation is needed to generate the best acuration of NMO velocity and residual move out, so the processed of muting data can be minimized. Some researchers have modified non-hyperbolic travel time equation. The purpose of modification is obtaining normal moveout (NMO) velocity more accurate so that the residual moveout value is smaller mainly in large offset to depth ratio (ODR). Hyperbolic traveltime equation was formulated by Taner and Koehler, but this equation is only accurate in offset to depth ratio (ODR)  1 [3]. Travel time equation was also modified by Alkhalifah, which derived from travel time equation with an-ellipticity parameter (  ). However, this equation in offset to depth ratio (ODR) < 2 [6]. Fomel and Stovas have also modified the equation, unfortunately, the accurately in offset to depth ratio (ODR)  2 [4]. Three years ago, Song et al. was modified the equation the accurate of this equation in normalized offset < 2 or offset to depth ratio (ODR)  4.5[5]. They suggest [4/3] and [7/6] order Padé approximation to applied for VTI media. The result obtained is the [7/6] order is better than [4/3] order Padé approximation. In this study, will use the modified travel time equation using Padé approximation in orde [7/6]. The approximation will be compared with hyperbolic, non- hyperbolic method by Alkhalifah, and Fomel and Stovas method to see the best accuration, which indicates the smallest residual reduction. The best method of the travel time with the smallest residual can be applied for increasing the image quality. , (201 https://doi.org/10.1051/e3sconf/201 E3S Web of Conferences 125 9) 9125 ICENIS 2019 15005 15005 © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).