波阻抗多约束反演

Multiply constrained acoustic impedance inversion

海洋石油勘探开发研究中心, 河北新城074000

Research Ccnter of Offshore Oil Exploration and Development, Xineheng City, Internal Postcode 074000

当前流行的恢复波阻抗的方法是用人工方法从叠加速度中提取低频分量, 然后加入到相对阻抗中去形成绝对波阻抗。这种方法主观因素太强, 又存在着频率5Hz～10Hz左右的谱的缺口．不够可靠。此外, 还有一些纯数学的方法, 如时域最小熵的谱外推法等。但这些方法缺乏地质上先验信息构成的约束, 也存在着不可靠性。本文提出了一种多约束反演方法。它利用了声测井资料, 加入了地震记录所欠缺的低频和高频的约束, 也利用叠后保真剖面, 加入了中频约束和层位约束。因此, 能减少反演的多解性, 能较好地与声测对比；又由于加入了层位约束, 构造显示也较清楚。这种反演是一维的道反演, 又是批量运行, 具有使用方便和效率高的优点。

So far the absolute acoustic impedances are restored from relative ones by adding in low frequency components artificially cxtracted from stacking velocities. This procedure however suffers from its subjectivity and t he existcnce of a noteh at a frcquence range of 5-10 Hz. The time domain minimum entropy cxtrapolation is another pure mathomatical method for this end, it's however unreliable for lack of prior geological information as constraints. The paper presents a multiply constrained inversion technique which provides seismie records with constraints from low and high frequences and other constraints from medium frequences and strata by making use of sonic logging data and seismie data after true amplitude restoration and stacking, respectively. As a result, the ambiguity of solutions is reduced to improve the correlation with sonic logging data. The visibility of structures is also improve as a constribution of the constraints from strata, Moreovcr, the new method is a 1-D single trace invcrsion and runs in batches,so it has advantage of high cfficicncy and being easy to opcrate.