利用四井微测井观测数据估算近地表Q值

近地表品质因子估算及补偿已经成为高分辨率地震勘探的重要研究内容之一。微测井因其施工简单、成本较低被广泛应用于近地表结构调查。常规微测井观测数据受震源子波差异和检波器耦合响应差异影响,严重降低了近地表Q值估算精度,导致近地表吸收结构调查结果存在很大的不确定性。从生产实际出发,分析实际测井数据,探究常规微测井观测系统调查近地表吸收结构的局限性。采用四井微测井观测系统,提出一种同时消除震源子波差异和检波器耦合响应差异影响的近地表Q值估算方法。该方法联立多个直达波信号,经过合理运算,不但完全消除了震源子波差异和检波器耦合响应差异对Q值估算的影响,而且通过优选频带,有效规避了近场和高频噪声。中国东部某工区实际资料应用结果表明,该方法能获得稳定可靠的近地表Q值,采用基于波场延拓的反Q滤波技术补偿近地表吸收衰减,吸收补偿后的地震资料分辨率得到有效提高。

Near-surface quality factor estimation and compensation have become an important field of research for high-resolution seismic exploration.Uphole surveys are widely used to investigate near-surface structures because of their simple operation and low cost.However,the conventional method is affected by differences in the response of source wavelet and geophone coupling,which significantly reduce the estimation accuracy of the near-surface Q value,and there is substantial uncertainty in the investigation results of near-surface absorption structure.Therefore,a new four-hole observation system for estimating the near-surface Q factor is proposed herein to simultaneously eliminate the influence of the differences in response of source wavelet and geophone coupling.The influence of near-field and high-frequency noise on Q factor estimation is effectively eliminated by optimizing the frequency band range.Application results showed that the proposed method can obtain a stable and reliable near-surface Q factor.Therefore,absorption compensation can be applied to the seismic data using an inverse Q filter based on wave field continuation.The resolution of the seismic data significantly improved after absorption compensation.

“辽河油田千万吨稳产关键技术研究与应用”项目(2017E-1602)资助。