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近地表地层品质因子在川西北部地区地震勘探中的应用
Application of near-surface formation-quality factor to seismic prospecting in northwestern Sichuan Basin
杨智超,李敏,张璐,陈江力,张孟
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作者单位:东方地球物理勘探公司西南物探分公司
中文关键字:双井微测井 近地表 Q 值 谱比法 综合属性 模型 柘坝场
英文关键字:Twin-well microlog; Near-surface; Q value; Spectral ratio method; Attribute integration; Model; Zhebachang
中文摘要:川西北部地区近地表地层松散,低降速层厚度变化大,导致地震波传播衰减较强,严重影响地震资料的信噪比和分
辨率。因此必须对采集的原始资料进行合理的吸收衰减补偿,而以往近地表地层品质因子(Q)常用一个点的成果代表一个区域,
很难反映该地区复杂地表Q 值的变化情况。故基于双井微测井数据,利用谱比法求取单点的Q 值,通过拟合得到纵波速度与Q
值之间的关系式,再结合精细的表层速度结构调查成果,获得了复杂地表浅层Q 值结构模型的构建方法。结果表明:①针对岩性
分层较多的近地表结构,采用综合属性分层可以增加每一层的Q 值计算样点,从而降低计算结果的误差;②利用双井微测井和大
炮初至信息,构建的近地表Q 值模型能真实反映近地表纵向和横向上随地形、岩性、低降速带厚度、速度的变化时Q 值的变化情况;
③利用这种Q 值模型对地震资料进行反Q 滤波,有效补偿了近地表对地震波频率和能量的衰减。
英文摘要:In northwestern Sichuan Basin, most near-surface formations are loose, and great variation in thickness for low subweathered
zones, all leading to strong decay of wave propagation. Both signal-to-noise ratio (SNR) and resolution of seismic data are impacted
severely. So, it's necessary to conduct a rational absorption decay compensation to primary data acquired. Previously, however, the
near-surface Q value often took the result of one point to represent the whole area, which might hardly reflect the whole variation of this
Q value. In this study, based on twin-well microlog data, single-point Q value was at first calculated by means of spectral ratio method.
Then, the relational expression between P-wave velocity and Q value was established through fitting. Finally, on the basis of investigation
on surface velocity structure, a method to construct Q value structure model was developed for shallow strata with complex surface.
Results show that, (1) for some near-surface structures with multiple lithological layers, to implement both attribute integration and layers
classification may increase sample number to calculate Q value of each layer, so as to decrease calculation error; (2) the near-surface
Q value model based on twin-well microlog and first arrival information can reflect truly that, Q value changes vertically and laterally
with the variation of landform, lithology, subweathered-zone thickness, and near-surface velocity; and (3) when this model is used to
conduct inverse Q filtering, the frequency and energy decay of near-surface seismic wave are compensated effectively.
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国内统一连续出版物号:CN51-1159/TE |国内发行代码: |国际标准出版物号:ISSN1673-3177 |国际发行代码:
主管单位:中国石油西南油气田公司  主办单位:中国石油西南油气田公司勘探开发研究院
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