Objectives/Scope

Creeping shale formations has over the last decade actively been used as permanent barriers for plugging & abandonment of wells across the North Sea. This paper gives an insight in how an innovative one trip system has been used to help qualify the Lower Hordaland formation as a barrier for plugging & abandonment of wells on the Gyda Field on the Norwegian Continental Shelf.

The Gyda Field is in the North Sea 280 km southwest of Stavanger in 66 meters of water. The Gyda reservoir is Upper Jurassic shallow marine sandstone at a depth of approx. 4000 meter. The evaluation and integration of data from wells drilled on the Gyda Field has concluded that the following formation groups are potential inflow zones that needs to be isolated in the permanent plugging of the wells Gyda reservoir, Farsund, lower Åsgard, and cretaceous/tertiary Inflow Group Forties/Lista.

The permanent plugging & abandonment of the 32 wells on the Gyda Field started in Q-1 2019, and needed an effective approach to qualifying creeping shale as a permanent barrier.

Methods, Procedures, Process

This approach was based on logging behind the 9 5/8" casing using an ultrasonic logging tool to locate the Lower Hordaland shale creep. The shale was successfully identified on the first wells, and the next phase was to prove, and verify that the creeping shales sealing capability.

A one trip tool system consisting of a disconnect tool, by directional cup tool and TCP perforating guns was used to perforated the casing, straddle the perforations and test the hydraulic sealing capability of the Lower Hordaland Shale.

Results, Observations, Conclusions

The result was 3 successful formation tests qualifying the Lower Hordaland shale as a permanent barrier. This innovative approach has improved the overall efficiency of the permanent plugging and abandonment of the wells on the Gyda Field significantly.

This paper describes the extensive work process that has been performed to plan, execute and verify the integrity of the lower Hordaland formation as a permanent barrier for plugging & abandonment.

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