基于双差反演策略的时移地震AVO反演

Time-lapse seismic AVO inversion based on a doubledifference inversion strategy

叠前时移地震资料中包含着重要的振幅随炮检距变化(AVO)信息。对时移地震资料反演可以得到油藏开发前、后弹性参数的动态变化,进而能够勘探剩余油分布、优化注采方案、提高油田采收率等。但是由于不同年份时移地震数据间的反演不一致性常造成反演假象,导致不正确的解释结果。为解决上述问题,将时移全波形反演中的双差反演策略引入时移AVO反演;同时,使用改进的射线参数域地震纵波反射系数近似方程作为正演方程进行时移地震AVO反演。模型测试结果显示,所提的基于双差反演策略的时移地震AVO反演方法不易受基准模型的反演质量、基准模型反演和监测模型反演行为的不一致的影响,可以有效压制目标区域外的反演假象,使反演结果集中在目标区域,从而准确地反映储层变化,提高了目标区域的反演精度,并减小油藏解释的误差。该方法还具有较强抗噪性,可稳定、准确地反演储层的纵、横波阻抗变化,并有效地反映上覆地层压力变化造成的微小纵、横波阻抗变化。

The time-lapse pre-stack seismic data contains important amplitude variation with offset(AVO)information.The inversion of time-lapse seismic data can yield dynamic changes in elastic parameters before and after oil reservoir development,which is conducive to the exploration of remaining oil distributions,the optimization of injection-production schemes,and the enhanced oil recovery of oilfields.The inversion of time-lapse seismic data in different years,however,is inconsistent,which often leads to inversion artifacts and incorrect interpretation results.To solve the problem,this paper introduces the double-difference inversion strategy in time-lapse full waveform inversion(FWI)into time-lapse AVO inversion. Meanwhile,the improved approximate equation of the seismic P-wave reflection coefficient in the ray parameter domain is employed as the forward modeling equation for time-lapse seismic AVO inversion.The model tests indicate that the time-lapse seismic AVO inversion method based on the double-difference inversion strategy is not sensitive to the influence of the inversion quality of the baseline model as well as the inconsistency in inversion behaviors of the baseline model and the monitoring model.Moreover,it can effectively suppress artifacts outside the target area and concentrate the inversion results in the target area to accurately reflect the changes in the reservoir,which improves the inversion accuracy of the target area and reduces the errors of oil reservoir interpretations.With strong anti-noise performance,this method can also stably and accurately perform the inversion of the changes in the P-wave and S-wave impedance of the reservoir and effectively reflect the slight change in the P-wave and S-wave impedance caused by the pressure change of the overlying formation.