混合偏移技术在克深1号构造带成像研究中的应用
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摘要
克深1号构造依据构造成因划分为盐上、盐下两个构造层,其主体构造部位盐下目的层反射能量弱,反射特征差,资料信噪比低,地震资料偏移成像的难度较大。文章从复杂构造地质模型正演入手,讨论了复杂构造共中心点道集反射波不能同相叠加及建立在零偏移距假设条件下的叠后偏移技术难以获得精确归位的原因,认为这类地区资料的偏移处理应分叠前的部分偏移和叠后的剩余偏移两步进行,这确定了适应这类地区精确成像的叠前叠后混合偏移方法。对叠前叠后混合偏移处理中的速度模型建立、反射波聚焦、反射波归位等关键技术进行了研究,认为叠前的部分偏移处理能部分降低了倾角、速度因素在共中心点叠加时带来的影响,得到了目的层更清晰的叠加成像;叠后用剩余速度场对叠前部分偏移的聚焦叠加结果进行叠后剩余偏移处理,较好解决了复杂构造反射波的准确归位。实际资料的处理结果表明偏移质量有明显提高,对查清克拉苏构造带目的层的构造形态有重要意义。
According to structural genesis, the structural belt Keshen-1 may be divided into two structural layers, i.e. super-saltbody and infra-saltbody structural layers. The infra-saltbody target layer at the structural main part is of the characteristics as weak reflection potential, unnoticeable reflection feafure and low signal-to-noise ration, so that the seismic migration imaging is very difficult. Proceeding from the forward geological model of complex structure and by means of discussing the reasons why the in-phase stacking of the CMP gather reflected waves of the complex structure can’t be realized and the precise homing is difficult to be achieved by the poststack migration technique based on zero offset assumption, the authors consider that the seismic migration processing of this kind of structures should be divided into two steps, i.e. prestack partial migration and poststack residual migration, thus establishing the prestack and poststack hybrid migration method beneficial to the precise imaging of these structures. Through researching the key techniques, as velocity model establishment, reflected wave focusing and reflection positioning techniques, in the hybrid migration processing, it was thought that the prestack partial migration processing can partially reduce the effects the dip and velocity factors on the CMP stacking, thus obtaining much clearer stack imaging; and the poststack residual migration processing may be carried out for the focusing stack of prestack partial migration by residual velocity field, thus solving the problem of the precise homing of reflected waves of the complex structure. The processing results of actual data indicate that the migration quality was obviously enhanced, which is of great importance to ascertaining the structural shape of the target layer in Kelasu structural belt.
According to structural genesis, the structural belt Keshen-1 may be divided into two structural layers, i.e. super-saltbody and infra-saltbody structural layers. The infra-saltbody target layer at the structural main part is of the characteristics as weak reflection potential, unnoticeable reflection feafure and low signal-to-noise ration, so that the seismic migration imaging is very difficult. Proceeding from the forward geological model of complex structure and by means of discussing the reasons why the in-phase stacking of the CMP gather reflected waves of the complex structure can’t be realized and the precise homing is difficult to be achieved by the poststack migration technique based on zero offset assumption, the authors consider that the seismic migration processing of this kind of structures should be divided into two steps, i.e. prestack partial migration and poststack residual migration, thus establishing the prestack and poststack hybrid migration method beneficial to the precise imaging of these structures. Through researching the key techniques, as velocity model establishment, reflected wave focusing and reflection positioning techniques, in the hybrid migration processing, it was thought that the prestack partial migration processing can partially reduce the effects the dip and velocity factors on the CMP stacking, thus obtaining much clearer stack imaging; and the poststack residual migration processing may be carried out for the focusing stack of prestack partial migration by residual velocity field, thus solving the problem of the precise homing of reflected waves of the complex structure. The processing results of actual data indicate that the migration quality was obviously enhanced, which is of great importance to ascertaining the structural shape of the target layer in Kelasu structural belt.
引文
1 伍志明等.高陡复杂构造的地震成像技术进展.天然气工业,2004;(2)
2 李亚林等.川东南门场高陡构造的地震成像技术试验研究.天然气工业,2004;(4)
3 鲁烈琴等.三维叠前深度偏移技术在西部复杂地区的应用与效果.石油地球物理勘探,1997;32(5):703～708
4 HerberV.f-Kdepthmigration.62ndAnnintSEG Mtg,1992:935-938
5 张叔伦.相位移方法的两个新算法.CPS/SECEAGE北京’98国际地球物理研讨会,1998:494～497
2 李亚林等.川东南门场高陡构造的地震成像技术试验研究.天然气工业,2004;(4)
3 鲁烈琴等.三维叠前深度偏移技术在西部复杂地区的应用与效果.石油地球物理勘探,1997;32(5):703～708
4 HerberV.f-Kdepthmigration.62ndAnnintSEG Mtg,1992:935-938
5 张叔伦.相位移方法的两个新算法.CPS/SECEAGE北京’98国际地球物理研讨会,1998:494～497
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