Extended whipstock and mill assembly

A method for milling a window in a cased wellbore, the method comprising:

• selecting a mill having a cutting structure arranged and designed to mill a window in a well casing;
• selecting a whipstock having a plurality of ramp sections configured to move the mill in a lateral direction during milling of the window, the whipstock and mill being selected such that the configuration of the plurality of ramp sections cooperates with the cutting structure of the mill to adjust loading on the cutting structure of the mill and increase length of well casing milled;
• and
• milling the window in the well casing.

A cutting tool for cutting a window through casing disposed in an existing borehole, the cutting tool comprising:

• an attachment end portion adapted to couple to a drilling tubular;
• a cutting portion arranged and designed to cut through well casing disposed in an existing borehole;
• and
• a plurality of cutting elements disposed in a casing cutting section of the cutting portion, the plurality of cutting elements being sufficient in number to limit the absolute difference in calculated casing volume removed by radially adjacent cutting elements in the casing cutting section to less than about 35 percent.

A method of milling a window in a cased borehole, the method comprising:

• positioning a whipstock in a downhole location of a borehole in which a lateral borehole is desired, the whipstock having a plurality of ramp sections forming a ramp profile;
• rotating a tubular string carrying a mill disposed on a downhole portion of the tubular string;
• advancing the tubular string along the plurality of ramp sections of the whipstock, the ramp profile arranged and designed to deflect the mill into milling engagement with a wall of the borehole;
• milling a window through the wall of the borehole, each ramp section of the plurality of ramp sections having a length and angular orientation selected such that the window milled through the wall of the borehole permits components of a bottom hole assembly to experience a calculated dogleg severity no greater than about 8 degrees per 100 feet while negotiating the ramp profile of the whipstock and passing through the milled window.