Prediction of pore-dominated Carboniferous-Lower Permian carbonate reservoir at the Laoshan Uplift, South Yellow Sea Basin

Marine carbonate is a kind of important oil and gas reservoir in the Mesozoic- Palaeozoic on the Laoshan uplift of South Yellow Sea Basin. Due to lacking of drilling data and knowledge of heterogeneity of the carbonate reservoirs, seismic prediction is the only way for reservoir assessment in oil and gas exploration although it is a rather difficult. Taking the Carboniferous - Lower Permian limestone in the South Yellow Sea as an example, this paper analyzed the petrophysical characteristics and the logging - seismic response of the limestone. Petrophysical analysis reveals that the acoustic impedance of bioclastic limestone is higher than that of pure limestone and siliceous clastic rocks. The limestone with lower λρ has better petrophysical characteristics. Pre-stack simultaneous inversion technique is effective to predict the lithology and physical properties of the pore-dominated carbonate reservoir. The results further suggest that the Carboniferous - Lower Permian bioclastic limestone reservoirs are relatively developed on the Laoshan Uplift and strongly discontinuous and heterogenous. Reservoirs are mainly developed on ancient highlands, owing to the exposure to air of the limestone uplifted by the Indosinian tectonic movement, the filtration by freshwater and dissolution of limestone, which increased the secondary porosity of carbonate reservoir to some extent. Such reservoirs have been encountered in drilling cores. Therefore, the pore-dominated carbonate rocks with high porosity should be regarded as the first priority of petroleum exploration target for the Carboniferous - Lower Permian in the South Yellow Sea Basin.