【作者】 黄龙泽；

【导师】 刘怀山；

【作者基本信息】 中国海洋大学 ， 地球探测与信息技术， 2009， 硕士

【摘要】 在陆上地震勘探中,由于地表条件、人员疏忽等因素的影响会出现炮点定位不准确的情况;海底电缆施工过程中,由于洋流等因素的影响会使检波点的实际位置与预设位置不同,这些情况严重影响了后续的地震资料处理工作,因此需要对炮点或检波点进行二次定位。基于波动方程的炮点二次定位参考了常规地震偏移成像技术,将排列接收到的波场反向外推,使波场逐步收敛,最终波场收敛到炮点位置,以此来实现炮点二次定位。在具体实现中需要在地面划分网格,然后应用克希霍夫积分法反向外推波场,获得网格点的能量值,能量最高的网格点便是炮点位置。为了提高运算速度同时保证定位精度,在划分网格时需要先粗分网格,求得网格点能量值,然后在能量高的网格点区域重新细分网格,通过细分网格点的能量值来确定出炮点位置。在炮点二次定位中利用的主要是直达波的波场信息,因此在预处理时,需要突出直达波压制干扰波。文章分析了在不同信噪比下的波场收敛情况,在模型实验中信噪比为1.25时仍能准确实现炮点二次定位。波场外推的速度是炮点二次定位的一个重要参数,在选取速度时,以当地的地层速度为基准,在粗分的网格中进行速度扫描分析,获得最佳的波场收敛速度,然后用其进行波场外推,求得网格点的能量值,实现炮点二次定位。检波点二次定位主要应用于海底电缆。在海底检波点二次定位中,炮点位置已知而检波点位置未知,因此需要从多个炮点位置正向外推波场,使波场逐步延拓到检波点,以此来获得检波点的位置。在具体实现中需要从原始地震资料中抽取共检波点道集,然后在海底面划分网格,应用克希霍夫积分法正向外推波场获得网格点的能量值,能量高的网格点为检波点的真实位置。网格的划分原则与炮点二次定位一样,需要先粗分后细分。海底检波点二次定位中,同样选用直达波作为主要的波场信息,而直达波是通过海水传播到海底的,因此,波场外推的速度选用海水层的速度。基于波动方程的炮检点二次定位在模拟和实际地震资料处理中都得到了良好的效果,验证了这种方法的可行性。更多还原

【Abstract】 There are lots of factors such as terrain configuration and people’s neglect which can influence the positioning of shotpoint for inshore seismic exploration. The real position of receiver is different from the designed for ocean bottom cable because of the influences such as ocean current. These factors seriously affect the sequent processing of seismic date, so it’s necessary to reposition the shotpoint and receiver.The secondary positioning of shot point utilizes the technology of seismic migration. The wave field data is extrapolated inversely which is accepted by the receiver, at last the wave field will be converged the position where the shot point is. After dividing grids on land surface, the wave field will be extraploated depends on the kirchhoff integration, then the wave field will be converged to the grids. The gird with high energy is the position where the shot point is. The gird’s interspacing is large when deviding the grid for the first time, then decrease the distance between the grids. Thus, the arithmetic can speed up, and the accuracy can be guaranteed. The direct wave is most important for the secondary positioning of the shot point. So the direct wave should be retained and the disturbing wave should be rejected. The paper analysises the constriction of wave field in different signal to noise ratio, the real position of the shot point can be found out for the simulating data when the signal to noise ratio is 1.25. The velocity of wave field extrapolation is important to the accuracy of the secondary positoning of shot point. The velocity bases on the formational velocity and scans in the grids when the interspacing of grids is large. When the velocity is confirmed, using the velocity to extrapolate the wave field to confirm the position of the shot point.The secondary positioning of receiver which is used for ocean bottom cable is different from the secondary positioning of shot point. Because the position of shot point is known, the wave fields can be extrapolated from lots of shot points, at last they all reach the position of receiver. Thus, the position of the receiver can be found out. The first step is dividing grids on the sea floor, then with the help of kirchhoff integration, the energy of the grids comes out, the grid with high energy is the position of the receiver. The rule of the dividing grid is same to the shot point. The direct wave is the most important information in the second positioning of receiver, and the direct wave propagates through the sea water. So the velocity should be the same to the velocity of the sea.Both the simulating and real data results confirm that the secondary positioning of shot point and receiver is feasible.更多还原