溶洞型储层成像分辨率分析

结合塔河油田溶洞型储层的特点,通过大量的数值模拟,分析了溶洞绕射波的波场特征,深入探讨了溶洞成像纵向、横向分辨率的本质,定量分析了信噪比对溶洞成像分辨率的影响,并给出了图像分辨率的概念及意义。研究表明:①溶洞的绕射波尾巴长,要选取较大的偏移孔径才能使绕射波能量得到较好的收敛;②溶洞较小时串珠远大于溶洞真实大小,随溶洞尺度增大串珠逐渐接近于溶洞真实大小;③纵向上不同高度的溶洞,如果连续地排在一起,实际上类似于一楔形体,其振幅变化呈调谐曲线;④传统的菲涅耳带半径不宜作为成像横向分辨率的评价参数,溶洞横向、纵向分辨率以λ大小为宜;⑤成像信噪比的改善趋势与炮集信噪比成反比,低信噪比资料成像处理后,溶洞的可识别度能得到明显提高;⑥要重视计算机图像分辨率的概念,注意高密度勘探最佳道距的合理选取。

Analysis of karst cave imaging resolution

Combining the characteristics of karst cave reservoir in the Tahe oil field, the paper analyzes the characteristics of ca ve diffracted wave field, probes into the nature of vertical resolution and lateral resolution in depth, and quantitatively analyzes the influence of signal noise ratio （SNR） to cave imaging resolution through a large number of forward modeling. In the end, this paper also gives the concept and significance of the image resolution. The results as fellows： ①The tail of diffracted wave of the karst cave is fairly long, so we need select a larger migration aperture to get a better convergent of diffracted wave ener gy; ②The size of string beads is far greater than the real size of cave when cave is small, beads gradually close to real size in crease with cave; ③If karst caves which have different vertical height continuously line together, as a whole which actually simi lar to a sphenoid, its variety of amplitude presents tuning curve; ③ The traditional Fresnel zone radius should not be used as e valuation parameters of the imaging resolution, the size of lateral and vertical resolution is appropriate to λ; ④The improvable trend of the SNR of imaging is inversely proportional to the SNR of shot gather, caves identification can significantly improve after imaging process for low SNR shot data; ⑤ We should pay more attention to the concept of computer image resolution and the appropriate selection of trace interval in high density exploration.