Some Practical Aspects of Using VSP Interferometry in Horizontal Wells for Imaging Above and Below the Wellbore

With the increased number of horizontal wells being used to produce unconventional plays, there is a growing inventory of wells that can benefit from the use of interferometric processing methods. Seismic interferometry for VSPs in horizontal wells can move the surface shots to behave as if they are located at the positions of the receivers in the borehole. It removes the overburden travel path from the redatumed traces without using any velocity information or even surface shot statics. So an image can be made below the borehole using only the local velocity near the borehole. The added benefit of redatuming the shots into the borehole is that the upcoming reflected energy from changes in the lithology below the borehole can act like deep seismic sources allowing imaging of events above the borehole. It is also possible to redatum the receivers to the surface, making each shot into a receiver. This transforms the VSP data set into surface seismic data. I present some practical aspects of the method using synthetic examples to create a more intuitive understanding of the method.