Identifying updip pinch-out sandstone in nearshore subaqueous fans using acoustic impedance and the instantaneous phase in the Liangjia area, Yitong Basin, China

Drilling has shown that there is a large petroleum reserve in the Sheling Formation in the Liangjia area of the Yitong Basin from reservoirs of the nearshore subaqueous fan facies. To reduce the risk associated with exploration, the updip pinch-out or isolated sandstone in the nearshore subaqueous fan should be identified and described. Analysis of the 3D seismic reflection, instantaneous phase and acoustic impedance was conducted to identify and interpret the sandstone. Seismic reflection, instantaneous phase and acoustic impedance alone can not clearly identify the updip pinch-out of sandstone in the nearshore subaqueous fan. However, the combination data of acoustic impedance and the instantaneous phase has better detectability (it indicates the ability for identifying sandstone distribution) and is a more reliable indicator of the sandstone distribution than these seismic data alone. The sandstone and the updip pinch-out of the sandstone in the nearshore subaqueous fan can be identified more clearly and directly by the combination data of acoustic impedance and instantaneous phase than the 3D seismic reflection data alone. Combined analysis of the acoustic impedance and instantaneous phase in the sedimentary system is a valid approach for identification and description of the updip pinch-out sandstone or the isolated sandstone that can reduce the risk associated with exploration of lithological traps.

► The fans are modeled based on the geological and geophysical data. ► The combination data of impedance and the phase provide higher resolution. ► The updip pinch-out of the sandstone can be identified clearly by the combination data. ► The use of these two datasets is a new method for the sandstone description.