After preliminary geotechnical studies indicated that the seabed was more friable than anticipated, EDF EN decided that jacket foundations would take longer and cost more than traditional monopile and gravity foundations.
However, it will still use jacket foundations supplied by STX for the substations.
Rival consortium Iberdrola and Eole-RES still plan to use jacket foundations, supplied by STX, in the two projects they bid for in competition with EDF EN.
The Iberdrola consortium said it took account of the friable nature of the sea bed and the foundations "will be installed according to the specifications so that they are perfectly anchored."
Once the outcome of the tender is announced, selected bidders will have 18 months to carry out more detailed sea-bed studies as part of a full risk assessment.
In a separate move, EDF EN and STX have announced plans to collaborate on a new vessel capable of carrying up to eight turbines.