Casing exit systems are used to sidetrack a
wellbore for many reasons, including re-entry of an existing wellbore, drilling
a bottomhole assembly that has become stuck and is too costly to fish out,
severe formation or drilling problems, the need to change the direction of a
wellbore, or the need to drill multiple exits from a single wellbore.
Big Rig one-mill casing exit system is
retrievable and has two retrieval tool options to accommodate severe hole
conditions. A complete system includes a whipstock combination, an orientation
device, an anchoring device, and a milling tool. This system provides a quicker
kickoff with a higher build rate in short-radius drilling applications. Decreased
length of the whipstock and a milling assembly consisting of only one multi-section mill form a significantly shorter window exit bottomhole assembly
(BHA). The reduced-length BHA is capable of passing through higher doglegs in
the wellbore. Our whipstock system provides an effective means to exit casing
and provide a window to run drilling BHA, liners, and completion equipment
through.
Big Rig field-proven Multi-section Taper Mill
is featured with hardfaced milling cone, water displace groove, nozzle and
joint. From bottom to top, it could be divided into four sections and each
section has its own function. The most far bottom section is spherical shaped for
orientation and dressed with carbide. When doing the window cutting, once any
point of this spherical mill head touches the casing inner wall the milling
starts and the window will be enlarged evenly and gradually. Section III is the
major section to cut the window and when full-drift OD is reached, the length
of smooth section II will be used for stabilization, minimizing any unnecessary
casing damage. The last section of the mill is for final fine grinding of the window.
By using only one mill, the window is cut, enlarged and grinded.