Time-lapse 2D interpretation of gas migration in shallow sand layers – Compared to reservoir simulation

Abstract

The work presented focuses on an area of the North Sea influenced by an underground blowout from the Saga Petroleum well 2/4-14. When hitting an Upper Jurassic sandstone, the well kicked and after several attempts to gain control, the drill pipe was cut and a cement plug set. 9 seismic site surveys were acquired over a period of 17months in order to monitor the underground flow of hydrocarbons. Comparing observations from the acquired seismic data to reservoir simulations and a later 3D seismic survey over the area, it is found that hydrocarbons have charged sand layers close to the wellbore. The reservoir simulations support the findings from time-lapse 2D seismic data analysis and substantiate the argument that time-lapse 2D seismic is a useful tool for monitoring shallow gas leakage.