三维地震勘探恢复性放炮法变通问题的讨论

A Discussion on Alternative to 3D Seismic Restoring Shooting

受地物影响,炮点的理论变观方法(恢复性放炮法)只能是三维地震数据采集过程中的一种补救措施而已,它只保证了设计覆盖次数不变的目的,而不能保证道集内炮检距和方位角不变的目的。一方面,变观后要求所有的炮检距均满足最大炮检距的限定条件显得过于苛刻;另一方面,对地层倾角较大或煤层埋藏较浅的勘探区,一个区的最大炮检距允许值也不一定是一个确定的值,通常的做法是取平均值。据此,提出了三维变观80原则,即在变观炮点不多或不集中时,只要变观炮点记录中有80%的炮检距或不低于80%的道满足最大炮检距要求,就可认为变观是成功的。这种实用的变观方法,对三维地震勘探野外数据采集工作有较明确的指导意义。

Because of ground object influences,the theoretical transformation of shotpoint (restoring shooting) can only be a remedial measure during 3D seismic data acquisition.It can only ensure designed folds keep unchanged but cannot ensure geophone offsets and azimuths within a trace gather keep unchanged.On the one hand,it is too rigor to ask all the geophone offsets to meet the limitation of the maximum offset; while on the other hand,the maximum offset is not a deterministic value in high strata dip angle or shallow coal seam buried area, an usual way is averaging. Thus, the paper put forward a principle of ″3D transformation 80″, that is when there are less transformed shotpoints or they are not concentrated, if more than 80% offsets or more than 80% traces can meet the requirement of maximum geophone offset,it is reputed that the transformation is successful. This practical transformation method has guiding significance in field 3D data acquisition.