Optimization and application of prestack seismic attributes to the mapping of channel sandbodies: A case study from the South Turgay Basin in Kazakhstan

Abstract

The Jurassic lithologic traps are well developed in the South Turgay Basin, Kazakhstan. The river channels are developed in multiple stages in this basin and the sandbodies are isolated and poor in continuity. Their exploration has entered a highly-mature stage. Post-stack seismic data are mainly used to map the channel sandbodies at present, but the effects are not satisfactory. Based on the thorough analysis of the characteristics of pre-stack gathers of channel sandbodies, various approaches including wavelet stretch correction, quality factor Q compensation and partly angle stack were used to improve the imaging quality of the channel sandbodies and optimize pre-stack seismic attributes which can better reveal the characteristics of channel sandbodies. Stratigraphic slice and the basic geologic characteristics of the basin were integrated to map the spatial distribution of the channels in the study area. The following conclusions were obtained. (1) The provenience was located to the northwest. (2) Channel sands of at least five stages occurred in the three fourth-order sequences in J3ak. Among these five-stage channel sands, at least three stages were developed in the SQ8-2. During these stages, channel sand development was the most extensive and strongest and the inheritance feature was also very prominent. (3) The early SQ8-1 sequence is characterized by the filling of channel deposits in a lake basin, while the late SQ8-3 sequence is smaller in scale, revealing the shrinkage of water volume.