Method and apparatus for milling a zero radius lateral window in casing

摘要

A flexible milling assembly for milling an orifice through a well casing. The milling assembly can include a drive yoke, and a plurality of straight and split yoke assemblies—all linked together and to a cutter head with universal blocks that enable the components to pivot relative to each other. A string of joint tubing connected to a prime mover on the surface is used to lower the milling assembly into a well and supply the driving torque. A split shoe coupled to a guide tube is positioned within the well casing where the orifice is to be milled. The milling assembly is guided through a curved passage within the split shoe to bring the cutter head into contact with the well casing. A protector assembly can be provided to enclose and protect the milling assembly when it is tripping into and out of the well casing.

主权项

1. A milling assembly for milling an orifice in a well casing, comprising:
a flexible joint assembly that includes a drive yoke couplable to a drive tube that applies a rotational driving force to the flexible joint assembly, the flexible joint assembly including a plurality of straight yoke assemblies, a plurality of split yoke assemblies, and a cutter head, the drive yoke being pivotally joined to one of the plurality of straight yoke assemblies through a universal block, each of the plurality of straight yoke assemblies being pivotally joined to at least one of the split yoke assemblies through additional universal blocks, a distal most of the plurality of split yoke assemblies being pivotally joined with the cutter head through another universal block; a cylindrical split shoe having a passage for guiding the flexible joint assembly to bend toward an internal surface of the well casing where the orifice is to be milled; and a tubular sleeve that is disposed around the flexible joint assembly, the tubular sleeve being coupled to the drive tube by at least one shear pin, such that in response to the tubular sleeve engaging a proximal end of the cylindrical split shoe, the at least one shear pin is sheared through causing a momentary decrease in a weight of the drive tube that is detectable on a surface above the well casing, indicating that the flexible joint assembly is proximate to a location where the orifice is to be milled through the well casing, the cutter head being disposed at a distal end of the flexible joint assembly to contact the internal surface of the well casing and to mill the orifice through the well casing as the drive tube rotates the flexible joint assembly and the cutter head.