深层高陡地层零井源距垂直地震剖面初至波特征分析及拾取策略.

In deep and high-steep formation, the first arrival wave of vertical seismic profiling (VSP) with zero well spacing appears bifurcation phenomenon or multiple wave, which makes the traditional VSP first arrival picking method unable to meet the processing requirements. Aiming at the problem of first-arrival pickup of zero-offset VSP, Numerical modeling analysis method was used to clarify the reason for the anomaly of zero offset VSP first-arrival wave in deep high and steep formation, because the formation dip angle is larger, the seismic wave far away from the wellbore reaches the geophone before the vertical incident wave through the high-speed formation, and the larger the formation dip angle is, and the greater the difference between the upper and lower medium velocities is, and the more obvious the bifurcation phenomenon is. The numerical simulation results are in agreement with the first-arrival field characteristics shown in the actual data. Then on the basis of this, a strategy of continuous downward picking along the shallow "first wave" in-phase axis based on forward modeling is proposed, which has been applied in the zero-offset VSP processing of Zhonghan 1 well in Tarim Basin and achieved good application effect. [ABSTRACT FROM AUTHOR]