Research On Reflected Wave Migration Of Array Acoustic Logging

Reservoir exploration and development work is gradually turned from the conventional type to non-conventional reservoirs.These small covert unconventional reservoirs generally have the characteristics of strata faults,cracks,holes and other small geological structure around the borehole.However,due to the low resolution of conventional surface and VSP seismic exploration,and the conventional sonic logging can only measure a shallow radial depth,these methods are difficult to effectively detect small geological structure described above.As a new logging technology,acoustic reflection image logging with respect to seismic surveys and conventional acoustic logging has the characteristics of high resolution and deeper radial depth of investigation,can effectively detect the geological structure 10-20 m away from the borehole.Select the appropriate migration method for complex geological structure is very important.Since the resolution of post-stack migration conventional is not high enough and cannot be applied in areas that velocities change largely,so the application in complex geological conditions and unconventional reservoirs is limited.Despite the high computational efficiency of pre-stack time migration,but it is not for areas with dramatic changes in velocities.Compared with it,pre-stack depth migration has high resolution,and can adapt to the complex geological conditions and the geological structure that velocities change largely in lateral,it can more accurately describe these tiny structures.This paper deduced the two dimensional acoustic and elastic wave equation respectively at first.Then the finite difference was used in the simulation of elastic wave propagation under borehole conditions mode and the Fourier finite difference pre-stack depth migration imaging method was used in migration.Also studied the factors affecting the migration imaging result,including velocity model,SNR,invasion layer around the borehole,then put forward the effective solutions to address these factors.Finally,using a variety of theoretical models to do a migration imaging process,it proved the accuracy of pre-stack depth migration imaging by processing and analysis the results.