Coiled tubing drilling with supercritical carbon dioxide

A method for using at least one of a supercritical fluid and a dense gas to perform maintenance within an existing borehole formed by a drilling apparatus within a substrate of a geological formation, comprising the steps of:

• (a) providing a material that exists in one of a supercritical phase state and a dense gas phase state at a temperature and a pressure within the existing borehole;
• (b) ejecting a fluid stream of said material, said temperature and pressure causing at least a portion of said material in said fluid stream to exist in one of a supercritical phase state and a dense gas phase state;
• and
• (c) performing the maintenance in the existing borehole with said at least the portion of the material.

A system for using one of a supercritical fluid and a dense gas to perform maintenance related to an existing borehole within a geological formation, comprising:

• (a) a supply source for a material that exists in one of a supercritical phase state and a dense gas phase state at a temperature and a pressure found within the existing borehole;
• (b) a drillstring having a distal end and a proximal end, said distal end being in fluid communication with said supply source, a tool defining a fluid outlet being mounted on the proximal end, said drillstring defining a fluid path from said supply source to said fluid outlet;
• and
• (c) means for controlling at least one of a temperature and a pressure at said fluid outlet, so that the material supplied through the fluid outlet exists in at least one of a supercritical phase and the dense gas phase, the material being employed to perform maintenance in the existing borehole.

A system for using one of a supercritical fluid and a dense gas to perform maintenance related to an existing borehole within a geological formation, comprising:

• (a) a supply source for a material that exists in one of a supercritical phase state and a dense gas phase state at a temperature and a pressure found within the existing borehole;
• (b) a drillstring having a distal end and a proximal end, said distal end being in fluid communication with said supply source;
• (c) a downhole motor in fluid communication with said drillstring, such that a fluid moving through said drillstring into said downhole motor drives said downhole motor;
• (d) a tool defining a fluid outlet mounted on the proximal end of said drillstring, such that said tool is in fluid communication with said drillstring, said tool being drivingly rotated by said downhole motor;
• and
• (e) means for controlling at least one of a temperature and a pressure at said fluid outlet, so that the material supplied through the fluid outlet exists in at least one of the supercritical phase and the dense gas phase, the material being employed to perform maintenance in the existing borehole.