Methods and apparatus for forming a lateral wellbore

An apparatus for forming a lateral borehole from a cased wellbore, the apparatus comprising:

• a drill string having a drill bit disposed at a lower end thereof;
• a diverter disposed at an end of the drill bit with a temporary connection therebetween;
• a container, the container fixedly attached to a lower end of the diverter and constructed and arranged to house an exothermic heat source material;
• an anchor, fixable at a predetermined location in the cased wellbore;
• and
• a telescopic joint disposed between the container and the anchor, the telescopic joint movable from a retracted to an extended position, the exothermic material thereabove adjacent an area of cased wellbore where a window is to be formed when the joint is in the extended position.

A method of forming a lateral borehole from a cased wellbore, the method comprising:

• running an apparatus into a wellbore, the apparatus including a drill string, a drill bit, a diverter, a container having an exothermic heat source therein, a telescopic portion and an anchor;
• setting the anchor at a predetermined position in the wellbore whereby the exothermic heat source is adjacent the wellbore casing wall where the window will be formed;
• initiating combustion of the exothermic heat source, causing the heat source to remove the casing in the area where a casing window is to be formed;
• causing the telescopic joint to move from an extended to a retracted position after the window is formed, thereby locating the diverter adjacent the window;
• and
• lowering and rotating the drill string and drill bit to form the lateral wellbore.