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    多波地震在四川盆地致密砂岩气藏勘探中的应用

    Application of multi-wave seismic techniques in tight sandstone gas exploration in the Sichuan Basin

    • 摘要: 多波地震勘探在岩性识别、储层刻画及含气性预测方面具有显著优势,但由于纵波与横波传播机制不同,同一地质界面在纵波(PP波)与转换横波(PS波)数据中往往表现出不同的运动学和动力学特征,导致PP波与PS波之间难以实现高精度匹配,尤其在目的层内部信号较弱时,匹配难度进一步增大。通过构建与PS波相似的拟横波地震数据,在大尺度上对PP波与PS波数据进行匹配,并采用动态滑动时窗进行局部自动精细匹配,实现了目的层纵横波精确匹配。在此基础上,利用转换横波数据计算相对横波阻抗,构建初始三维岩相体并作为约束,对转换横波实施相控地质统计学反演,形成高精度的三维岩相体。进而以高精度三维岩相体为约束,对纵波数据开展相控地质统计学反演,获取相控纵波阻抗反演结果。结合相控横波阻抗反演结果,计算得到纵横波速度比,实现储层与含气性的有效预测。该逐级相控多波联合预测方法提升了储层及含气性预测的精度,验证井结果显示,储层厚度与含气性预测值与实测值误差较小,证明了该方法的有效性。

       

      Abstract: Multi-wave seismic exploration offers distinct advantages in lithology identification, reservoir characterization, and gas-bearing property prediction. However, due to different propagation mechanisms of compressional waves (P-waves) and shear waves (S-waves), the same geological interface often exhibits different kinematic and dynamic characteristics in reflected compressional wave (PP-wave) and converted shear wave (PS-wave) data. This makes high-precision PP-PS data registration challenging, especially when the target formation exhibits weak internal signals. By constructing pseudo-S-waves similar to PS-waves, PP- and PS-data are first matched on a large scale. Dynamic sliding time windows are then employed for local automatic fine matching, ultimately achieving accurate registration of PP- and PS-waves within the target formation. On this basis, relative S-impedance is calculated using the PS-data to construct an initial 3D lithofacies volume, which is then used as a constraint to perform facies-controlled geostatistical inversion on the PS-data, resulting in a high-precision 3D lithofacies volume. This lithofacies volume serves as a constraint for facies-controlled geostatistical inversion on the PP-data to obtain facies-controlled P-impedance volume. Inverted P-impedance is combined with S-impedance to calculate P- to S-velocity ratio, thereby enabling effective reservoir and gas predictions. This progressive, facies-controlled multi-wave joint prediction method enhances the accuracy of reservoir and gas predictions. Verification well results show small errors between predicted and measured values for reservoir thickness and gas-bearing property, demonstrating the effectiveness of the proposed method.

       

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