可控震源高效采集滑动时距曲线设计技术

Slip sweep time-distance curve acquisition design and application by vibroseis

可控震源系统非线性特性产生的谐波噪声对滑动扫描或时变滑动扫描等高效采集方法地震记录造成较大干扰。给出了高效采集滑动时间与相邻炮间距离关系,即滑动时距曲线设计方法,既能最大限度规避或减少谐波干扰,又能保持高效采集。通过谐波形成和特征研究,理论计算谐波在地震记录上的分布范围,数值模拟谐波对上一炮地震记录干扰规律。通过工区实际试验地震记录分析谐波能量在时间与距离上的关系,初至前谐波随时间从低频到高频能量减弱,多阶谐波重叠分布,并随阶次增加谐波能量快速降低。得到地震记录初至前谐波最小能量在时间与距离上的分布曲线——最小谐波能量曲线,以不使该曲线进入上一炮地震记录或干扰最深目的层反射为原则,设计相邻两炮可控震源距离与滑动时间的关系曲线,即滑动时距曲线。在SZ沙漠区设计了三种滑动时距曲线,进行时变滑动高效采集方法段试验。通过处理剖面分析,验证了滑动时距曲线设计方法的正确性和有效性,规避和减少了谐波干扰,保证了高效采集资料质量,提高了施工效率,取得了比较好的效果。

Seismic recording of slip sweep or time-varying slip sweep is highly disturbed by the harmonic noise generated by the non-linear characteristics of the vibroseis system. The relationship between the slip time and the distance between the adjacent shots is given, that is the design method of slip time-distance curve, which can not only avoid or reduce the most harmonic interference, but also maintain the efficient acquisition. Through the study of the harmonic formation and features, the distribution range of harmonic in seismic recording is calculated and the interference law of the last shot record is simulated by numerical simulation.By analyzing the relationship between harmonic energy and time-distance from the real experimental seismic data in field, the energy of the harmonic is weakened from low frequency to high frequency with the time before first arrive, and the multi-order harmonic distributed with overlap and reduced rapidly with the increasing harmonic order. So that the minimum harmonic energy distribution curve in the time and distance is get. In principle of no harmonic interfere with the deepest target layer reflection, the relation curve between the adjacent two shots slip distance and slip time, that is the slip time-distance curve, is designed. Three kinds of slip time-distance curves in the SZ desert area are designed also, and the time-varying slip sweep efficient acquisition method is tested. By the analysis of the seismic processing profile, the correctness and effectiveness of the time-distance curve designing method are verified to be correct and efficient, the harmonic interference is avoided or reduced, the quality of seismic data is ensured, also the data acquisition efficiency is improved, and the great results are achieved.