Study On The Radiation Characteristics Of The Cross-well Directional Source And Compensate Its Energy

As a bridge between the well logging data and seismic data,Cross-well seismic technology plays an important role in improving the application accuracy and resolution of seismic data.But the radiation energy of the directional source in the borehole has a direction because of the borehole coupling and the source attribute.This energy imbalance affects the continuity of reflection events in the recorded data,and it has certain influence on the migration imaging results.So it is necessary to study the mechanism of inter well source radiation energy direction is generated and the compensation for the unbalanced energy.This paper analyzes why the cross-well seismic has the directional radiation energy.Basing on two different ideas,circular source array method and absorption attenuation layer method are proposed respectively to modeling the directional source in the borehole.The circular source array method sets up the radiation characteristics of the source by setting the source analytical solution,while the absorption attenuation layer method decays the wave-field excited by point source different in different directions to realize the directional energy.The forward modeling of cross-well directional source is made by using these two methods,and the influence of the main parameters involved in the simulation method on the modeling results was analyzed.Through forward modeling,it proves that the directional radiation energy of cross-well seismic source leads to the decline of reflection wave energy with the increase of angle of incidence.Then design a method to separate the direct wave and pick up the distribution of the direct wave energy automatically by using the ratio of energy method.On the basis of the approximate Zoeppritz equation,the energy characteristic curves of the reflected wave energy can be derived from the distribution characteristics of the direct wave by using the relationship between reflection coefficient and the transmission coefficient.Adding the curves into the cross-correlation imaging condition as a parameter,then energy compensation is realized in the process of reverse time migration imaging.According to forward modeling,direct wave energy separation,characteristic curve extraction and reverse time migration processing,the effect on imaging section of cross-well seismic source is solved,and a satisfactory imaging section is obtained.