MsMr-VSP: A specialized VSP survey for high-resolution imaging of stratigraphic clinoforms for carbonate reservoir monitoring

Seismic imaging of thin stratigraphic features requires high frequency seismic data, accurate estimation of subsurface velocities and high-resolution imaging techniques for proper focusing of seismic energy. Borehole seismic surveys meet all of these requirements and are known to provide higher resolution subsurface images compared to surface seismic mainly because of shorter ray paths and consequently less anelastic attenuation of energy received in a borehole. However, when imaging focus is constrained within a certain depth range of the target reservoir, standard walkaway borehole seismic surveys suffer from large incidence angles at longer source offsets. The reflected seismic waveform at higher incidence angles experiences amplitude and phase variations that are undesirable for imaging. Herein, we present a novel borehole seismic survey geometry – "Moving-source Moving-receiver Vertical Seismic Profile" (MsMr-VSP), where the receiver array is moved up the hole starting at the target depth, while the source is moved away from the well-head. An application of the MsMr-VSP survey is presented from Abu Dhabi, where it was used for high-resolution and improved quality imaging of thin clinoform features in a carbonate reservoir with reasonably low reflection angles and a high reflection point density maintained at the target level along the extent of the clinoform.