Case Histories: Vertical Seismic Profiles
The literature is full of good examples of VSP success stories. These are just a few that I like. Be sure to correlate VSP results with logs and computed log results, such as a lithology - porosity display.

VSP in Faulted Section
Example shows VSP, dipmeter, and synthetic traces from sonic and density logs. Note the clear evidence of a fault on the dipmeter, which helps to explain why the log traces and VSP inversion do not tie.



Dipmeter with fault


VSP, sonic, and inversion with fault

VSP in Overpressured Section
Example shows seismic section and VSP overlay. Overpressure indications on VSP inversion trace predict required mud weights and potential drilling difficulty. Sonic and density trace from logs in final hole confirm the presence of overpressure at the same depth as the VSP prediction.


VSP used to predict top of overpressure zone

VSP in Deviated and Horizontal Hole
Example shows original seismic section and VSP with time scale gamma ray logs from two wells. Gamma ray defines sands of interest. VSP shows major fault through sand. This fault and others are drawn on a reprocessed, migrated seismic section, along with tracks of development wells. Gamma ray profile on each well again defines the sands. Finally a blowup of the seismic inversion section over the sand shows track of horizontal hole. The wellbore track is shown black where measurement while drilling gamma ray log indicated shale and white for sands.


VSP with gamma ray logs


Inverted VSP with well tracks and GR logs

Compare the original seismic map with dome shaped, faulted interpretation to the final map, which gives an entirely different picture of en-echelon faults. Future drilling will be greatly influenced by this change in the prospect orientation and shape.


Original interpretation (left), new interpretation (right)
 

Page Views ---- Since 01 Jan 2015
Copyright 1978 - 2017 E. R. Crain, P.Eng. All Rights Reserved