Prediction of fractured-vuggy reservoirs within the Ordovician buried hills in the Qianmiqiao block, Huanghua depression

Gas reservoirs occurring within the Ordovician buried hills in the Qianmiqiao block of the Dagang oilfield have been identified for over two decades. However, the hydrocarbon accumulation model and enrichment patterns of these reservoirs remain unclear, leading to a torturous exploration and exploitation process, along with difficulties with the effective production of proven reserves. In recent years, with the advancement in related studies, researchers have gradually recognized the controlling effects of fractured-vuggy carbonate reservoirs on hydrocarbon accumulation and enrichment, changing the previous view of structurally controlled, layered hydrocarbon reservoirs. To predict fractured-vuggy reservoirs, this study employed high-accuracy 3D seismic data tailored to reservoir imaging. Through fine-scale reservoir calibration, the seismic responses of the fractured-vuggy reservoirs were determined. To achieve lateral identification of their planar positions and the vertical delineation of their top and bottom boundaries, this study conducted seismic facies identification and seismic facies-driven constrained sparse spike inversion (CSSI) by fully mining the reservoir information implicit in seismic data and innovating technical approaches. As a result, the spatial distribution of fractured-vuggy reservoirs was predicted. The prediction results, consistent with geological laws and aligning highly with actual drilling results, provide strong support for the selection, design, and deployment of efficient well locations in the fractured-vuggy carbonate reservoirs hosted by buried hills in the Qianmiqiao block. The results also serve as a reference for research on hydrocarbon reservoirs within buried hills in similar blocks of the Bohai Bay Basin.