Application of pseudo-acoustic waveform inversion technique in predicting CO₂ storage reservoirs in the Yantai Depression, South Yellow Sea

Carbon dioxide geological storage can reduce emissions and sequester carbon and is a key approach to achieving carbon neutrality goals. The Cenozoic sandstone reservoirs distributed in the Yantai Depression of the South Yellow Sea Basin have good development conditions and significant carbon storage potential. Due to the severe overlap of wave impedance between sandstone and mudstone, strong stratigraphic heterogeneity, and widespread thin interbedding in the Yantai Depression, traditional seismic reservoir prediction methods struggle in effectively identifying rock types and reservoir boundaries. Based on 2D seismic and drilling data, petrophysical analysis and seismic inversion were conducted, for which pseudo-acoustic inversion technology was adopted to improve the accuracy of sandstone and mudstone recognition, and reveal preliminarily the vertical and horizontal distribution patterns of the Cenozoic sandstone reservoirs. Results shows that pseudo-acoustic inversion technology could effectively solve the problem of poor correspondence between wave impedance and lithology, and improved significantly the accuracy of lithology recognition. The inversion results indicate that four sets of reservoirs are developed vertically in the study area with varying physical properties and thicknesses. The Lower Yancheng Formation (Miocene) is the main reservoir with the largest thickness and best physical properties, while the reservoirs of the Sanduo Formation (Oligocene), Dainan Formation (Eocene), and Funing Formation (Paleocene) are relatively thinner but also have certain storage potential. Horizontally, the reservoirs exhibit superiority in pattern in the north and inferiority in the south, with the best reservoirs in the Lower Yancheng Formation in the Penglai Sag in the north, followed by the Qixia Sag in the middle, and the poorer reservoir development conditions in the Haiyang Sag in the south. This research provided a basis for site selection for carbon storage in the Yantai Depression.