An Electrokinetic Approach for Reducing Spudcan Base Suction

Suction at the base of an installed spudcan dictates the extraction resistance. Consequently, any reduction of the base suction will ease the extraction process and reduce offshore time and hence cost. This paper experimented the potential of using electrokinetic phenomena for reducing the base suction. Electrolysis of pore water was occurred by electrode reaction when an electric current is applied through an electrode inserted into a saturated clay deposit. This resulted in formation of a gas layer (and hence gap) underneath the base of the spudcan. To evaluate the effectiveness of creating a thin gas layer and reducing the base suction, model tests were conducted. Additionally, the safety concerns associated with the application of electric current in the sea were addressed through numerical simulations considering all the values in prototype scale. In summary, the base suction could safely be reduced through the formation of a thin gas layer. Additional energy is required to generate the gas layer; however, the energy consumption for spudcan extraction using electrode reaction was much smaller than using conventional methods such as water jetting, reverse circulation, spudcan vertical cycling. Offshore time required for a spudcan extraction or jack-up leg retrieval would also be significantly shorter.