System and methods for creating shaped, non-circular boreholes in rocks especially for use with
geothermal heat pump applications and for increasing
wellbore support in applications such as horizontal oil and gas drilling are described. The systems and methods when applied to geothermal heat pumps create an elliptical shaped hole that is optimized for placing
heat transfer tubes with a minimum of
grout used. The significantly reduced cross-sectional area of the elliptical borehole also increases the overall drilling rate in rock and especially in hard rocks. In horizontal hard-rock drilling, creation of a horizontal non-circular borehole or modification of a circular borehole to a non-circular geometry is used to stabilize the borehole prior to casing
insertion, and may also allow the use of lower mud pressures improving drilling rates. The
system uses a non-contacting
drilling system which in one embodiment uses a supersonic
flame jet
drilling system with a movable
nozzle that swings between pivot points. In a second embodiment the elliptical shaped hole is created by an
abrasive fluid or particle bearing-fluid or air jet
drill that moves between pivot points. In another embodiment a non-contacting
drill can use dual parallel nutating nozzles that create a pair of overlapping circular holes. The non-circular shaped hole is created by either the high temperature
flame or water-particle jet or chemically active fluid jet as it removes rock material by
erosion,
dissolution and or thermal spalling. Modifications of circular boreholes to a generally elliptical shape can also be done using milling or jetting techniques.