井间地震反射波成像技术探讨

The reflection imagine of seismic crosshole.

井间地震反射波的主频大约是地面地震反射的10倍,因而井间地震具有更高的分辨率,同时对成像精度的要求也就更高。以VSP-CDP成像方法为例,探讨了影响井间地震反射波成像质量的因素,指出井间直达波可作为检验成像精度的依据;在总结和比较井间和地面地震反射成像方法差异的基础上,提出无需速度建模的走时场延拓反射波成像方法,并推导出弱各向异性介质下纵波的走时延拓方程。实际井间资料的处理结果表明,走时场延拓反射波成像方法较之井间VSP-CDP反射成像方法的成像质量有了质的提高,其成像剖面与地面地震剖面相比,包含了更多的地层信息,由此说明,新的成像方法是可行和可靠的。

Compared to surface seismic, seismic crosshole has the higher resolution; the dominant frequency of crosshole is about the decuple quantity of the former.As the result, imaging of crosshole request more accuracy than surface.Factors of VSP-CDP mapping quantity for crosshole reflection are discussed,and point out that accuracy of imaging could be evaluated by firstbreak (direct wave). A new imaging method without velocity model by extrapolating traveltime of first break is presented,which based on travel-time equation of compress wave derived in weak anisotropy media, considering the difference of reflection imaging between surface and borehole survey. Results of field data demonstrated that the new method is reliable and feasible