番禺4洼古近系储层叠前反演预测技术研究
Pre-stack inversion for prediction of the Paleogene reservoirs in the Panyu 4 Sag
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摘要: 针对少井且构造沉积双复杂的古近系地层,为了提高储层反演精度,首先在地震资料处理时,采用稀疏脉冲反演一次波估算和各向异性Q叠前深度偏移两项关键技术,提高了地震道集质量和成像品质,然后采用叠前同时反演方法开展研究工作。方法步骤如下:①使用叠加速度,通过层约束Dix反演获得纵波阻抗低频模型;②使用分角度叠加数据和经过井震标定的子波进行弹性阻抗反演,得到远、中、近道弹性阻抗体;③通过Fatti反演,获得初始纵波阻抗、初始横波阻抗和初始密度;④开展叠前同时反演,获得最终的纵波阻抗、横波阻抗和密度;⑤利用岩性和物性反演结果,预测储层展布范围。该方法基于三维地震数据驱动,且对测井依赖程度低,可为类似地质条件下的储层预测工作提供借鉴。Abstract: To improve the inversion accuracy of reservoirs in the Paleogene strata with limited wells and sedimentary and structural complexity, two key technologies were used in seismic data processing: sparse pulse inversion for primary wave estimation and anisotropic Q-pre-stack depth migration (PSDM). This contributed to improved quality of seismic gathers and imaging. Then, the pre-stack simultaneous inversion method was applied as follows: (1) Stacking velocity and layer-constrained Dix inversion were employed to obtain a low-frequency model of P-wave impedance; (2) Elastic impedance inversion was performed using angle-stacked data and well-calibrated wavelets, yielding far, medium, and near elastic impedance; (3) Initial P- and S-wave impedance, as well as initial density, were obtained through Fatti inversion; (4) Pre-stack simultaneous inversion was performed to obtain the final P- and S-wave impedance and density; (5) Lithology and physical property inversion results were used to predict the reservoir distribution range. This method, driven by three-dimensional seismic data and exhibiting low dependence on logs, can serve as a reference for reservoir prediction under similar geological settings.
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