地震资料提高分辨率处理技术在乐山—龙女寺古隆起龙王庙组勘探中的应用

近几年的研究成果表明,四川盆地乐山—龙女寺古隆起斜坡上的下寒武统龙王庙组是重要的天然气勘探目标,但在地震剖面上龙王庙组顶界不易对比追踪,其储层识别困难,有必要开展有针对性的提高地震资料分辨率的处理技术攻关研究。为此,采用了以下技术措施:约束层析静校正加剩余静校正技术来提高静校正精度;叠前保真去噪技术提高资料信噪比;井控地震资料处理技术进行高频补偿,提高纵向分辨率;精细速度建模及叠前偏移技术提高横向分辨率及成像质量。最终获得的地震成果剖面主频为35~38Hz,频宽8~70Hz,分辨率及信噪比明显提高。对于龙王庙组储层厚度30m以上的地区,储层地震响应特征清楚,井、震匹配较好,龙王庙组滩体叠置接触关系清楚。但对于储层单层厚度小于20m的地区,在已提高分辨率处理的地震剖面上仍难以识别龙王庙组储层,需要通过地震正反演或提高地震采集原始资料的有效频宽来实现薄储层的地震识别。

Application of resolution improvement in seismic data processing technology to the Longwangmiao Fm gas reservoir exploration in Leshan Longnüsi Paleouplift,Sichuan Basin

Research in recent years has demonstrated that the Cambrian Longwangmiao Fm reservoirs on the slope of the Leshan Longnüsi Paleouplift are extremely prospective in natural gas exploration. However, on the seismic profile, it is hard to compare and trace the top boundary of Longwangmiao and to identify the reservoir bed. Therefore, the resolution of seismic data is necessary to improve. To this end, the constrained tomographic static correction technology and residual static correction technology were first applied to improve the seismic data resolution. Then, the pre stack high fidelity noise attenuation technology was employed to improve the signal-to-noise ratio of the data. Moreover, the well control seismic data processing technology was utilized for high frequency compensation and longitudinal resolution improvement. And finally the fine velocity modeling and pre stack migration technologies were used to improve the horizontal resolution and imaging quality. As a result, the final seismic profile had a dominant frequency of 35~38 Hz and a bandwidth of 8~70 Hz. Therefore, its resolution and signal-to-noise ratio were significantly improved. As for such reservoirs with the thickness of above 30 m, the reservoir seismic response features are clear, the seismic and logging data are well matched, and the stack and contact relation of Longwangmiao Fm facies are extremely clear. However, as for such reservoirs with the thickness of below 20 m, it is still difficult to identify the Longwangmiao Fm reservoir bed on the seismic profile undergoing resolution improvement, but this can be achieved by conducting seismic forward modeling and inversion or by improving the effective bandwidth of the original seismic acquisition data.