高精度三维地震勘探中的炮密度、道密度选择——YA高精度三维勘探实例
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摘要
与常规地震采集参数,如覆盖次数和面元大小等相比,在高密度三维地震采集设计中,讨论炮密度和道密度参数对叠前成像的影响显得更为重要。在导出炮密度、道密度与面元、覆盖次数的关系的基础上,通过对YA高精度三维观测系统及其五种退化方案叠前偏移效果、信噪比和采集成本的对比分析,本文认为:①由于地震数据的频带是有限的,叠前偏移效果与炮密度、道密度关系曲线存在一个门槛值,在门槛值内信噪比随炮密度或道密度的增加而明显增大,超过该门槛值,再增加炮密度或道密度时信噪比仅有微弱改善;②不同地区、不同深度的目标体炮密度或道密度门槛值是不一样的,构造简单地区的门槛值小,构造复杂地区的门槛值大,目的层浅的门槛值大,目的层深的门槛值小。因此,高精度三维勘探的炮密度和道密度的选择必须与构造复杂程度、地震勘探频带相适应,且应优先确定;面元和覆盖次数的选取只需满足炮密度和道密度的要求即可;减小组合基距或采用单点接收和高分辨率处理能拓宽频带,这两者会使炮密度和道密度相应提高;不应过分强调小面元、高覆盖次数,这样就使采集参数有更大的优选空间,真正体现基于叠前成像的观测系统设计的理念。
When comparing acquisition parameters in routine seismic exploration,such as fold,bin size and so on,discussion on the influence of shot density and trace density to pre-stack imaging in high density 3D seismic acquisition design seems more important.Base on the derived relationship between shot density/trace density and bin/folds,and by comparison and analysis of pre-stack migration effects,signal to noise ratio and acquisition cost between high precision 3D geometry design in YA area and its 5 degradation designs,the following conclusions were obtained in this paper:(1).As the bandwidth of the seismic data is limited,a threshold exists for relationship curve of pre-stack effect,shot density and trace density,under the threshold the signal to noise ratio increases with the shot density and trace density,however over the threshold,the signal to noise ratio only could improve a little bit if increasing shot density and trace density.(2).For different areas and targets buried in different depth there are different thresholds,the more complicated the areas are,the bigger the thresholds will be,and the shallower the targets are,the bigger the thresholds will be.Therefore selection of the shot density and trace density in high precision 3d needs to match the structural complexity and seismic exploration bandwidth,that should be determined with priority.It will be ok if the selected bin and fold could meet the need of the shot density ant trace density.Decreasing interval of geophones or adopting single receiver acquisition and high resolution processing could expand frequency bandwidth,the two measures could raise the shot density and trace density accordingly,no need to pay much attention to the small bin and high fold so that the acquisition parameters could have bigger optimization space,the idea of designing the geometry based on the pre-stack imaging can be truly reflected.
When comparing acquisition parameters in routine seismic exploration,such as fold,bin size and so on,discussion on the influence of shot density and trace density to pre-stack imaging in high density 3D seismic acquisition design seems more important.Base on the derived relationship between shot density/trace density and bin/folds,and by comparison and analysis of pre-stack migration effects,signal to noise ratio and acquisition cost between high precision 3D geometry design in YA area and its 5 degradation designs,the following conclusions were obtained in this paper:(1).As the bandwidth of the seismic data is limited,a threshold exists for relationship curve of pre-stack effect,shot density and trace density,under the threshold the signal to noise ratio increases with the shot density and trace density,however over the threshold,the signal to noise ratio only could improve a little bit if increasing shot density and trace density.(2).For different areas and targets buried in different depth there are different thresholds,the more complicated the areas are,the bigger the thresholds will be,and the shallower the targets are,the bigger the thresholds will be.Therefore selection of the shot density and trace density in high precision 3d needs to match the structural complexity and seismic exploration bandwidth,that should be determined with priority.It will be ok if the selected bin and fold could meet the need of the shot density ant trace density.Decreasing interval of geophones or adopting single receiver acquisition and high resolution processing could expand frequency bandwidth,the two measures could raise the shot density and trace density accordingly,no need to pay much attention to the small bin and high fold so that the acquisition parameters could have bigger optimization space,the idea of designing the geometry based on the pre-stack imaging can be truly reflected.
引文
[1]曲寿利.高密度三维地震技术——老油区二次勘探的关键技术之一.石油物探,2006,45(6):557～562
[2]钱荣钧.关于地震采集空间采样密度和均匀性分析.石油地球物理勘探,2007,42(2):235～243
[3]熊翥.高精度三维地震(I):数据采集.勘探地球物理进展,2009,32(1):1～11
[4]张永刚等.单点高密度地震数据处理分析与初步评价.石油地球物理勘探,2010,45(2):201～207
[5]王海等.观测系统对高密度地震采集资料的影响.石油地球物理勘探,2009,44(2):131～135
[6]赵殿栋.高精度地震勘探技术发展回顾与展望.石油物探,2009,48(5):425～435
[7]Sehroeder F W等著;高林译.覆盖次数和面元尺寸怎样影响数据可解释性.石油物探译丛,1999,(1):19～32
[2]钱荣钧.关于地震采集空间采样密度和均匀性分析.石油地球物理勘探,2007,42(2):235～243
[3]熊翥.高精度三维地震(I):数据采集.勘探地球物理进展,2009,32(1):1～11
[4]张永刚等.单点高密度地震数据处理分析与初步评价.石油地球物理勘探,2010,45(2):201～207
[5]王海等.观测系统对高密度地震采集资料的影响.石油地球物理勘探,2009,44(2):131～135
[6]赵殿栋.高精度地震勘探技术发展回顾与展望.石油物探,2009,48(5):425～435
[7]Sehroeder F W等著;高林译.覆盖次数和面元尺寸怎样影响数据可解释性.石油物探译丛,1999,(1):19～32
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