Application of AVO Information-constrained Matching Pursuit Technique in Rich Coal Reservoir Characterization
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摘要: 针对西湖凹陷富煤环境下储层刻画精度低问题,本文结合煤层AVO截距、梯度特征,提出一种基于AVO信息约束的匹配追踪技术,压制煤层强反射引起的岩性假象,凸显储层真实、有效信号。该方法首先利用煤层4类AVO负强截距P、正强梯度G特点,构建煤层地震敏感因子P - G,放大煤层地震响应,并压制非煤层强振幅影响,实现煤层位置精细定位;在此基础上,将该煤层地震信息作为匹配追踪需要分解、重构的原始信号,利用复地震道分析技术提高信号快速匹配分解的效率,完成煤层强反射解耦。模型试算及实际资料应用表明:匹配追踪技术在精细定位煤层地震响应基础上,提高了匹配追踪算法去煤层强振幅效率;煤层解耦后地震数据较好地凸显储层横向展布变化,提高主力气层的纵向刻画精度。Abstract: To address the low accuracy of reservoir characterization in XiHu Sag in a coal-rich environment, this study developed a matching pursuit technology based on AVO information constraints combined with the AVO intercept and gradient characteristics of coal. It can suppress the strong reflectance lithologic artifacts caused by coal and highlight actual and effective reservoir signals. Based on the negative intercept P and positive gradient G of the AVO of coal, the seismic–sensitive factor P–G of coal identification was developed to amplify the seismic response of coal and suppress the high-amplitude response of non-coal. Then, to accurately identify the location of coal, the seismic information of coal was used as the original signal that needs to be decomposed and reconstructed by matching pursuit. Additionally, the efficiency of signal-matching decomposition was improved using the technology of complex seismic track analysis. Finally, the strong reflection elimination of coal was completed. Model trials and practical applications indicate that this method could accurately identify the seismic response location of coal and improve the efficiency of the matching pursuit algorithm. Moreover, the coal-eliminated seismic data can better highlight the lateral distribution changes of the reservoir and improve the vertical characterization accuracy of the main gas layer.
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表 1 靶区不同岩性弹性参数
Table 1. Elastic parameters of different lithologies in the target area
岩性 Vp/(m/s) Vs/(m/s) 密度/(g/cm3) 纵波阻抗/
((m/s)·(g/cm3))泥岩 4150 2220 2.65 10998 Ⅲ 类砂岩 3500 2375 2.40 8400 Ⅱ类a型砂岩 4600 2750 2.49 11454 Ⅱ类b型砂岩 4300 2610 2.47 10621 Ⅰ类砂岩 5300 3250 2.55 13515 煤层 2900 1500 2.00 5800 表 2 靶区不同岩性截距P、梯度G及P–G值
Table 2. Intercept P, gradient G, and P–G of different lithologies in the target area
岩性 截距P 梯度G P-G Ⅲ 类砂岩 -0.135 -0.123 -0.012 Ⅱ类a型砂岩 0.020 -0.183 0.203 Ⅱ类b型砂岩 -0.017 -0.147 0.130 Ⅰ类砂岩 0.103 -0.357 0.460 煤层 -0.301 0.369 -0.670 -
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