# 复杂波场页岩气探区速度分析方法探讨A Discussion on Velocity Analysis Method of Shale Gas Exploration Area with Complex Wave Field

DOI: 10.12677/JOGT.2018.406117, PDF, HTML, XML, 下载: 459  浏览: 1,490

Abstract: The wave field of XC Shale Gas Exploration Area was complex, and the stacking velocity was difficult to obtain. The velocity analysis by superposition energy method could not meet the processing requirements. This paper combined the characteristics of seismic data in the XC Shale Gas Exploration Area, focused on the impact of factors such as low signal-to-noise ratio and near-surface anomalies on the quality of the velocity spectrum, the targeted processing techniques and methods were proposed, a set of methods for precise extraction of seismic stack velocity in XC Shale Gas Exploration Area were summarized. Firstly, the original data were purified and the noise was suppressed by multi-domain and multi-method combination, and the signal-to-noise ratio was improved. Secondly, various residual static correction methods were used for maximally reducing the problem of high frequency static correction and improving the quality of seismic data. Finally, the relevant characteristics of instantaneous phase and the statistical phase correlation method were used to calculate the velocity spectrum, improve the precision of calculating speed. Better imaging results are obtained; especially the quality of structural imaging in the middle and deep layers is obviously improved.

1. 引言

2. 速度分析基本原理

2.1. 叠加能量法

$A=\frac{1}{N}{\sum }_{j=1}^{M}\left({\sum }_{i-1}^{N}{f}_{i,j+{r}_{i}}\right)$ (1)

2.2. 统计相位相关法

1) 设输入的道集为uij，表示第i道、第j个采样点。设初始时间为t0，选定其对应的速度v进行动校正，此时可以得到校正后的道集，再应用Hilbert变换法求取uij的瞬时振幅Aij和瞬时相位μij

2) 将整个道集分为若干部分，即样点分布分为c组，样点的相位表示为 ${\mu }_{is}\left(i=1,2,\cdots ,{n}_{s};s=1,2,\cdots ,c\right)$ ，且 ${\sum }_{s=1}^{c}{n}_{s}=M$ ，求取统计量R和W：

$R=\sqrt{{\left({\sum }_{s=1}^{c}{U}_{s}\right)}^{2}+{\left({\sum }_{s=1}^{c}{W}_{s}\right)}^{2}}$ (2)

$W=2\left({\sum }_{s=1}^{c}\frac{{R}_{s}^{2}}{{n}_{s}}-\frac{{R}^{2}}{M}\right)$ (3)

R假设检验与W假设检验是判断t0及所选定的v正确与否的标准。当R检验假设概率分布是单峰分布时，代表t0及所选定的v正确；当W检验假设概率分布在不同偏移距范围内，且都是相同的单峰分布时，代表t0及所选定的v正确。

3) 计算常规叠加能量的瞬时信息SB(t, v)：

${S}_{\text{B}}\left(t,v\right)=\frac{{\sum }_{i=1}^{M}B\left[{\sum }_{j=1}^{N}{u}_{ij}\left(t,v\right)\right]}{{\sum }_{i=1}^{M}L\left\{{\sum }_{j=1}^{N}B\left[{u}_{ij}\left(t,v\right)\right]\right\}}$ (4)

4) 计算能量函数SRWB

${S}_{\text{RWB}}=\left(\frac{R}{W}\right){S}_{\text{B}}$ (5)

3. 应用实例效果分析

3.1. 速度分析的预处理

3.1.1. 提高信噪比处理

Figure 1. The single shot result before (a) and after (b) denoising

Figure 2. The profile correlation before (a) and after (b) denoising

3.1.2. 剩余静校正处理

Figure 3. The profile correlation before (a) and after (b) residual static calibration

3.2. 统计相位相关法速度谱的求取

Figure 4. The velocity spectrums of different velocity analysis methods

Figure 5. The stack profiles of different velocity analysis methods

4. 结语

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