Real-time reflection point density mapping during three-dimensional (3D) vertical seismic profile (VSP) surveys

A method of generating a three dimensional (3D) vertical seismic profile (VSP) comprising:

• A) planning a 3D-VSP survey plan around a borehole based at least in part on an existing velocity model, the planning including planning a pattern of surface source points and selecting at least one subsurface target reflector;
• B) dividing the subsurface target reflector into a plurality of bins and assigning at least one surface source point to each bin, wherein the 3D-VSP survey plan further comprises a fold threshold for each bin, and for each bin,
• 1) firing at least one source at the surface source point assigned to the bin at a source firing time,
• 2) acquiring subsurface data as a result of the source firing,
• 3) updating the existing velocity model in real-time based on the acquired subsurface data,
• 4) calculating, in real time prior to a subsequent source firing for the bin, a fold value for the bin based on the updated velocity model,
• 5) comparing, in real time prior to a subsequent source firing for the bin, the the fold value for the bin to the fold threshold for the bin and,
• a) if the fold value for the bin is not within the fold threshold for the bin, repeating parts (1) through (5) for other source points assigned to the bin, or
• b) if the fold value for the bin is equal to or greater than an upper limit of the fold threshold for the bin, activating at least one source at a subsequent source point assigned to a subsequent bin and repeating parts (1) through (5) for each subsequent bin until the calculated fold value for each subsequent bin is equal to or greater than a lower limit of the fold threshold for the bin, for all bins.