Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fo...Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.展开更多
在深层油气藏勘探中,地震波能量屏蔽现象(如煤层、膏盐层等)严重制约了深部目标层反射信号的清晰度,单一地震属性难以全面表征复杂地质条件。时频电磁法(Time Frequency Electromagnetic Method,TFEM)基于电磁波在不同地质体传播差异,...在深层油气藏勘探中,地震波能量屏蔽现象(如煤层、膏盐层等)严重制约了深部目标层反射信号的清晰度,单一地震属性难以全面表征复杂地质条件。时频电磁法(Time Frequency Electromagnetic Method,TFEM)基于电磁波在不同地质体传播差异,可有效穿透高阻、高速屏蔽层,在深部岩石属性探测与储层预测中具有独特的穿透能力。近年来该技术在深层油气勘探方面取得突破:研发了新一代发射系统;创新地提出双侧激发多线同步采集技术和四方位全覆盖同步激发采集技术,显著改善了照明均匀性,降低了阴影效应与各向异性影响。在处理技术方面,创新地提出了一种分步递进反演策略,这种方法核心在于构建多源数据协同约束与分步递进反演策略,通过渐进式优化,实现反演精度的层级提升。理论正反演模拟验证了方法的合理性与有效性,并在中国西部塔里木盆地8000 m超深井储层预测及东部深层火成岩储层评价中取得了显著的应用成效。展开更多
基金the National Key Research and Development Program of China(No.2016YFC060110403).
文摘Herein,a three-dimensional(3D)inversion method in the frequency domain based on a time–frequency transformation was developed to improve the efficiency of the 3D inversion of transient electromagnetic(TEM)data.The Fourier transform related to the electromagnetic response in the frequency and time domains becomes a sine or cosine transform under the excitation of downward-step current.We established a transformation matrix based on the digital fi ltering calculation for the sine transform,and then the frequency domain projection of the TEM data was determined from the linear transformation system using the smoothing constrained least squares inversion method,in which only the imaginary part was used to maintain the TEM data transformation equivalence in the bidirectional projection.Thus,the time-domain TEM inversion problem was indirectly and effectively solved in the frequency domain.In the 3D inversion of the transformed frequency-domain data,the limited-memory Broyden–Fletcher–Goldfarb–Shannoquasi–Newton(L-BFGS)method was used and modifi ed with a restart strategy to adjust the regularization parameter when the algorithm tended to a local minimum.Synthetic data tests showed that our domain transformation method can stably project the TEM data into the frequency domain with very high accuracy;furthe rmore,the 3D inversion of the transformed frequency-domain data is stable,can be used to recover the real resistivity model with an acceptable effi ciency.
文摘在深层油气藏勘探中,地震波能量屏蔽现象(如煤层、膏盐层等)严重制约了深部目标层反射信号的清晰度,单一地震属性难以全面表征复杂地质条件。时频电磁法(Time Frequency Electromagnetic Method,TFEM)基于电磁波在不同地质体传播差异,可有效穿透高阻、高速屏蔽层,在深部岩石属性探测与储层预测中具有独特的穿透能力。近年来该技术在深层油气勘探方面取得突破:研发了新一代发射系统;创新地提出双侧激发多线同步采集技术和四方位全覆盖同步激发采集技术,显著改善了照明均匀性,降低了阴影效应与各向异性影响。在处理技术方面,创新地提出了一种分步递进反演策略,这种方法核心在于构建多源数据协同约束与分步递进反演策略,通过渐进式优化,实现反演精度的层级提升。理论正反演模拟验证了方法的合理性与有效性,并在中国西部塔里木盆地8000 m超深井储层预测及东部深层火成岩储层评价中取得了显著的应用成效。
