Excavating deposits from an underground formation layer

A method of excavating deposits from an underground formation layer, comprising:

• drilling a well assembly, which penetrates the underground formation layer at a first, a second and a third location, which locations are triangularly spaced;
• drilling from these locations a channel assembly that traverses the formation layer and interconnects the locations;
• inserting a chain cutter string into a first section of the channel assembly that is located between the first and second locations;
• inserting a chain cutter control cable from the third location into a second section of the channel assembly;
• connecting the chain cutter control cable to the chain cutter string at a branchpoint of the first and second sections of the channel assembly;
• pulling the chain cutter string through the first section of the channel assembly while exerting a lateral force to the chain cutter string by the chain cutter control cable such that the chain cutter string is pressed against the wall of the first section of the channel assembly and is thereby induced to carve deposits from the underground formation layer;
• and
• flushing carved out deposits through the channel assembly and the well assembly.